managing groundwater and surface water for native ... · south australia; melaleuca halmaturorum...

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© 2002 CSIRO To the extent permitted by law, all rights are reserved and no part of this publication covered by copyright may be reproduced or copied in any form or by any means except with the written permission of CSIRO Land and Water. Important Disclaimer: CSIRO Land and Water advises that the information contained in this publication comprises general statements based on scientific research. The reader is advised and needs to be aware that such information may be incomplete or unable to be used in any specific situation. No reliance or actions must therefore be made on that information without seeking prior expert professional, scientific and technical advice. To the extent permitted by law, CSIRO Land and Water (including its employees and consultants) excludes all liability to any person for any consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using this publication (in part or in whole) and any information or material contained in it.

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EXECUTIVE SUMMARY In addition to the damage caused to agriculture, infrastructure and water resources, dryland salinity is increasingly being recognised as a major cause of degradation of natural ecosystems in Australia. The National Land and Water Resources Audit (NLWRA, 2001) highlights that 630,000 hectares of remnant native vegetation and associated ecosystems are currently at risk, and that these areas are projected to increase by up to 2 million hectares over the next 50 years. Many areas predicted to be at risk of dryland salinity by 2050 contain National and State Nature Conservation Areas and Wetlands of International Importance. As a result, State and Federal policies on dryland salinity now recognise the need to protect these important natural assets, as well as agricultural land, water resources and urban infrastructure. As a result, natural resource managers are increasingly expected to protect areas of native vegetation that are affected by shallow saline groundwater.

Unfortunately, knowledge of groundwater and surface water interactions with native vegetation has lagged behind understanding of the other impacts of salinity. However, over the last 10 years, there have been a number of laboratory, lysimeter, field and modeling studies to investigate the interaction between soil, vegetation, groundwater and salt in areas of shallow saline groundwater. These include a range of vegetation types and environmental conditions (soils, groundwater and climate).

This report summarises the recent understanding described above in a guideline form that is useful for natural resource managers so that they can better predict likely native terrestrial vegetation responses to a range of management options. In this report the term natural resource managers refers to those involved in technical investigations (i.e. botanists, ecologists, hydrogeologists, hydrologists), those responsible for on-ground management of native vegetation, and those setting policy directions for the protection of native vegetation. While the latter are an audience for these guidelines, it is important to note that the guidelines do not specifically address policy and legislative requirements. Moreover, the guidelines have not received endorsement from any of the jurisdictions they may encompass, and as such represent the views of the authors only.

The report is broken up into several parts.

Part 1 is concerned with a range of background material.

• Chapter 1 outlines the background, objectives, scope and intended audience of the report. The guidelines are targeted at native terrestrial vegetation communities that are subject to occasional inundation and increasing salinisation due to groundwater rise. The primary vegetation communities of interest are those considered to be of conservation value where technical investigations are warranted.

• Chapter 2 outlines the issues associated with the impact of rising saline groundwater on native vegetation by discussing previous studies of relevance, providing some key examples and relating the issues to Federal and State policies and strategies, and Australia’s international obligations.

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Part 2 is concerned with identifying the processes of salinisation and the response of vegetation.

• Chapter 3 deals with groundwater discharge processes at the scales of the entire catchment, the discharge area and at specific sites. The combination of groundwater discharge, which includes seepage, evaporation from the land surface, groundwater uptake by vegetation, and soil leaching at different sites leads to different patterns of salt accumulation. Time scales for salt accumulation vary widely and are governed by depth and salinity of groundwater, climatic conditions, soil texture, plant water use and salt tolerance characteristics, and the frequency of significant leaching events. All of these variables contribute to the salt balance. This pattern of salt accumulation through groundwater discharge must be balanced by salt losses through leaching or run-off.

• Chapter 4 deals with plant responses to salinity, waterlogging and drought that include groundwater use by vegetation, thresholds and time scales for salt accumulation under vegetation, the concept of a critical water table depth and its shortcomings, specific plant physiological responses, and generalised responses of Australian native vegetation to salinity and waterlogging. The latter highlights the current lack of knowledge regarding the interaction between groundwater, surface water and vegetation due to a paucity of field studies of native communities. It is important to note that our knowledge of the responses of Australian native tree species to salinity, waterlogging and drought is predominately based on laboratory and glasshouse studies and a few field studies concerned primarily with revegetation rather than natural systems.

• Chapter 5 presents field-based case studies that illustrate the range of impacts of salinity on native vegetation health. These include: Eucalyptus largiflorens communities of the Chowilla Floodplain, Lower River Murray South Australia; Melaleuca halmaturorum communities of the Upper South-East, South Australia; Casuarina and Melaleuca communities of Toolibin Lake, Western Australia; and other selected Australian studies. To date these are the only comprehensive field-based studies in existence. While the lack of field studies makes it difficult to generalise, the limited data suggest that Melaleuca and Casaurina spp. are more salinity and waterlogging tolerant than Eucalyptus spp. which in turn are more tolerant than Acacia spp. It is clear that further field-based studies are required to enhance our knowledge of a wider range of species and communities so as to manage the impacts of the predicted increases in salinisation into the future.

Part 3 describes approaches and techniques for the assessment, monitoring and management of the health of native vegetation communities.

• Chapter 6 deals with planning a groundwater discharge investigation at the catchment, discharge area and site scales. Scoping investigations using mostly existing data for desktop assessments are discussed. These include initial assessment of site physical features, vegetation mapping and health assessment, airphoto interpretation and remotes sensing, topographic survey, groundwater depth and salinity, electromagnetic (EM) induction survey, soil type, salinity and water status profiles, inundation/flooding information, and

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climate. More detailed methodologies for identifying vegetation at risk, assessing its health status and determining the causes and processes leading to the risk are discussed. These include measurements of plant water stress, plant water use, identification of plant water sources, groundwater discharge estimation, remote sensing vegetation survey and vegetation growth modelling. The degree to which the more detailed approaches are used will depend on the conservation value of the community concerned and the available resources.

• Chapter 7 discusses some of the considerations when designing management plans for threatened vegetation communities. With very few exceptions, it will not be possible to completely restore a native vegetation community back to its natural condition. It is therefore important to clearly identify what is achievable for a given situation. Management goals can be summarised into three main categories: (i) recovery of the ecosystem; (ii) containment of further impacts; and (iii) adaptation to the new salinity regime. The decision will be based on the financial and technical resources available, ecological significance of the area and its current health, stakeholder aspirations, and other considerations. In most instances tradeoffs will be needed.

• Chapter 8 describes the techniques available for an ongoing plan to monitor progress of the improved management of a native vegetation community affected by salinity. As it will generally be a long-term process, the montoring plan should include well-designed and communicated protocols for sampling, and data management and review. Water table and salinity changes in time, photopoints and detailed vegetation growth monitoring are essential components of a plan.

Part 4 provides a brief summary of the report. Chapter 9 presents some concluding remarks whilst Chapter 10 presents the author’s views of the obvious gaps in the knowledge base.

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TABLE OF CONTENTS EXECUTIVE SUMMARY .......................................................................................................I TABLE OF CONTENTS....................................................................................................... IV ACKNOWLEDGEMENTS.................................................................................................... VI GLOSSARY ....................................................................................................................... VII

BACKGROUND ...............................................................................................................1

CHAPTER 1. OBJECTIVES, AUDIENCE AND SCOPE .........................................................3 BACKGROUND .....................................................................................................................3 OBJECTIVES.........................................................................................................................3 SCOPE ..................................................................................................................................4 AUDIENCE ...........................................................................................................................6 CHAPTER 2. DEFINITION OF THE ISSUES.........................................................................7 PREVIOUS STUDIES..............................................................................................................7 KEY EXAMPLES OF PROCESSES, VALUES AND ECOLOGICAL IMPORTANCE. ......................7 RELATIONSHIP TO EXISTING FEDERAL AND STATE POLICIES.............................................9

PROCESSES ...................................................................................................................11

CHAPTER 3. GROUNDWATER DISCHARGE....................................................................13 CATCHMENT......................................................................................................................13 DISCHARGE AREA .............................................................................................................14 SPECIFIC SITE ....................................................................................................................15 CHAPTER 4. PLANT RESPONSES TO SALINITY, WATERLOGGING AND DROUGHT .....16 GROUNDWATER USE BY VEGETATION..............................................................................16 THRESHOLDS FOR SALT ACCUMULATION UNDER VEGETATION.......................................17 PLANT PHYSIOLOGICAL RESPONSES .................................................................................19 GENERALISED RESPONSES OF AUSTRALIAN NATIVE VEGETATION TO SALINITY AND WATERLOGGING................................................................................................................21 IMPACTS OF CLIMATE VARIABILITY .................................................................................24 CHAPTER 5. CASE STUDIES ............................................................................................25 EUCALYPTUS LARGIFLORENS COMMUNITIES OF THE CHOWILLA FLOODPLAIN, LOWER RIVER MURRAY (SOUTH AUSTRALIA) ..............................................................................25 MELALEUCA HALMATURORUM COMMUNITIES OF THE UPPER SOUTH-EAST (SOUTH AUSTRALIA) ......................................................................................................................29 CASUARINA OBESA AND MELALEUCA COMMUNITIES OF TOOLIBIN LAKE (WESTERN AUSTRALIA) ......................................................................................................................31

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OTHER SELECTED AUSTRALIAN STUDIES......................................................................... 34

ASSESSMENT, MONITORING AND MANAGEMENT .......................................... 37

CHAPTER 6. ASSESSMENT ............................................................................................... 39 PLANNING GROUNDWATER DISCHARGE INVESTIGATION ................................................ 39 SCOPING INVESTIGATIONS ................................................................................................ 42 DETAILED MEASUREMENTS.............................................................................................. 49 CHAPTER 7. MANAGEMENT ........................................................................................... 54 GOAL SETTING .................................................................................................................. 54 CONSIDERATIONS IN SELECTING AN APPROPRIATE OPTION............................................. 55 CHAPTER 8 MONITORING .............................................................................................. 57 WATER TABLE AND SALINITY CHANGES IN TIME ............................................................ 57 PHOTOPOINTS .................................................................................................................... 59 DETAILED VEGETATION GROWTH MONITORING.............................................................. 60

SUMMARY ..................................................................................................................... 61

CHAPTER 9. CONCLUDING REMARKS ........................................................................... 63 CHAPTER 10. KNOWLEDGE GAPS.................................................................................. 64

REFERENCES................................................................................................................ 65

APPENDICES ................................................................................................................. 79

APPENDIX 1: DETERMINING MOISTURE, CHLORIDE AND OSMOTIC SUCTION CHARACTERISTICS OF SOIL SAMPLES ........................................................................... 81 APPENDIX 2: FILTER PAPER METHOD OF MEASURING MATRIC SUCTION OR POTENTIAL ON LOOSE SOIL SAMPLES ........................................................................... 83 APPENDIX 3: ATTRIBUTES FOR INDEX OF VEGETATION HEALTH: LAY AND MEISNER (1985) METHOD ............................................................................................... 85 APPENDIX 4: ATTRIBUTES FOR INDEX OF VEGETATION HEALTH: ELDRIDGE (1993) MODIFICATION OF GRIMES (1987) METHOD ...................................................... 86 DIAGRAMS DEPICTING VEGETATION HEALTH INDEX ATTRIBUTES ................................. 87 DIAGRAMS DEPICTING VEGETATION HEALTH INDEX ATTRIBUTES (CONTINUED)........... 88

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ACKNOWLEDGEMENTS This document was funded as part of Project CLW8 (Guidelines for Managing Groundwater for Vegetation Health in Saline Areas) which is managed by Land & Water Australia, formerly known as the Land and Water Resources Research and Development Corporation, a statutory authority within the Commonwealth Department of Agriculture, Fisheries and Forestry – Australia. We would also like to thank a number of stakeholders who provided valuable feedback on this report: Dr. Richard George (Dept. of Agriculture, Western Australia, Bunbury), Andy Spate (National Parks and Wildlife Service, Queanbeyan), Bernie Dunn (Wimmera Catchment Authority, Horsham), Mark Reid and Rexine Perry (Centre for Land Protection Research, Bendigo), and Peter C. Smith, Peter L. Smith and George Gates (Department for Land and Water Conservation, Parramatta).

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GLOSSARY Note: Many of the following terms are not strict scientific definitions, being rather more colloquial explanations of their meaning and significance. Anoxia: lack of oxygen in the soil due to waterlogging.

Aquifer: a saturated permeable soil or geologic unit that can transmit significant quantities of groundwater under a hydraulic gradient.

Capillary rise: the upward movement of groundwater through the soil caused by the surface tension of water in soil pores. When water tables rise to near the surface, drying of soil by evaporation and transpiration leads to high rates of capillary rise of groundwater. This is an important form of groundwater discharge and if the groundwater is saline then this process leads to salt accumulation in the soil profile.

Catchment: an area of land bounded by topographic or geologic features within which rainfall and/or groundwater drains to a particular point such as a stream or lake.

Dynamic equilibrium: refers to how a groundwater system/soil hydrology responds to naturally varying rainfall rather than any land use change. Land use change usually results in a transformation to a new dynamic equilibrium.

Evapotranspiration: loss of water to the atmosphere by evaporation from the soil surface and by transpiration from plants.

Groundwater: sub-surface water in soils and geologic strata that have all of their pore space filled with water (i.e. are saturated).

Groundwater discharge: the loss of water from a groundwater system (aquifer) to the atmosphere by evaporation, springs and/or transpiration over a given period.

Groundwater recharge: the addition of water to a groundwater system, most commonly through infiltration of a portion of rainfall, floodwater or irrigation water that moves down beyond the plant root zone to an aquifer.

Halophyte: plants that grow naturally in high concentrations of salt, and require some salts for optimum growth.

Hydraulic gradient: the change in hydraulic head in an aquifer with either horizontal or vertical distance, in the direction of groundwater flow.

Indigenous terrestrial vegetation: naturally occurring native vegetation growing on the land surface (i.e. not in water bodies such as streams, lakes and wetlands).

Ion toxicity: adverse effects of specific ions of salt in a plant that has difficulty in regulating the amount and type of salt taken up by the roots.

Isotope: atoms with the same number of protons but different numbers of neutrons. The slight difference in mass changes some of their physical and chemical properties. Measurement of the ratio of the concentration of the stable isotopes of water and carbon (2H, 18O, 13C) to their normal form (1H, 16O, 12C) can be a useful means of

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tracing sources of water. Use of isotopes that radioactively decay such as 3H and 14C can be a means of determining the age of water or plant material.

Isotopic signature: naturally occurring ratios of stable isotopes to normal elements in plant and animal tissue, soils and water.

Leaching: the removal of salt from the soil profile by water applied at or near the soil surface (rainfall, floodwater, irrigation). This water drains down through the soil profile taking salt with it.

Leaf area index: the ratio of total single-sided leaf surface area to the area of the canopy projected onto the ground.

Leaf or plant water potential: a measurement that provides an indication of the water status of a plant. It is reported as a negative number with the minimum observed value providing a measure of the plants ability to extract water from soils under extreme drought and/or saline conditions.

Natural resource manager: a person responsible for the management of any aspect of the natural environment.

Osmotic effects: plant stress and dieback due to physiological drought. Even though adequate water may be available in the soil profile, high concentrations of salt affect the ability of the plant to extract water from the soil (the osmotic potential is too low for the water to be available to the plant).

Physiological adaptations: adaptations as a result of climatic, edaphic, and biotic factors acting on an organism that result in it being better suited to its environment.

Remnant native vegetation: any remaining indigenous native vegetation regardless of the number of trees.

Root zone: the part of the soil profile where plant roots are active.

Salinity threshold: salinity level at which plant growth or health is inhibited.

Salt accumulation: when saline water tables rise near to the soil surface evaporation and water uptake by plants leads to a build up of salts left behind in the soil profile.

Salt balance: when the mass of salt entering a soil profile, groundwater system or catchment is balanced by an equivalent mass of salt exiting the area over the same time period. An example is a catchment in which the mass of salt entering the catchment via rainfall is equal to that leaving the catchment by stream flow at its outlet.

Sap water: water moving in the plant xylem from the roots to the leaves in response to transpiration.

Soil matric suction or potential: the amount of energy required to remove water held in soil pores due to the forces of surface tension. Can be reported as either a

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positive (suction) or negative (potential) number and is a measure of the dryness of the soil that is independent of soil texture.

Soil osmotic suction or potential: the amount of energy required to move water through a membrane that is permeable to water but not to solutes (in this context the membrane is a root surface). Can be reported as either a positive (suction) or negative (potential) number and is a measure of dryness of the soil to plants due to salinity.

Transpiration: loss of water vapour and other gases from leaves and other plant surfaces to the atmosphere. Also referred to as plant water use or uptake.

Water balance: a state of equilibrium where rainfall or irrigation water in a soil profile, groundwater system or catchment is accounted for by the sum of run-off, transpiration, evaporation, recharge and changes in soil moisture content.

Waterlogging: when a soil profile becomes saturated by either inundation or rising water tables entry of oxygen into the soil is limited. Once all of the existing oxygen in the soil has been used, plants will begin to dieback due to the anoxic conditions, as water uptake by plant roots requires adequate oxygen. Some plant species have adaptations that enable them to better survive such saturated conditions.

Water table: the level of groundwater in an unconfined aquifer. The soil pores and geologic strata below the water table are saturated with water.

WAVES: (Water, Atmosphere, Vegetation, Energy and Solutes) a one-dimensional numerical model of the groundwater-soil-vegetation-climate continuum, which accounts for the major processes affecting vegetation growth and water use and salt transport in soils underlain by a shallow fluctuating water table.

part one Background

CHAPTER 1. OBJECTIVES, AUDIENCE AND SCOPE

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Background Recent National Land and Water Resources Audit findings (NLWRA, 2001) suggest that approximately 5.7 million hectares of Australia’s agricultural and pastoral zone are within areas mapped to be at risk or affected by dryland salinity. Moreover, they predict that by 2050 as much as 17 million hectares may be at high risk. In addition to the damage to agriculture, infrastructure and water resources, dryland salinity is increasingly being recognised as a major cause of degradation of natural ecosystems in Australia. NLWRA (2001) suggests that of the area currently mapped to be at risk, 630,000 hectares of this is remnant native vegetation and associated ecosystems, and that these areas are projected to increase by up to 2 million hectares over the next 50 years. As shown in Figures 1 and 2, many areas predicted to be at risk of dryland salinity by 2050 contain National and State Nature Conservation Areas and Wetlands of International Importance. As a result, State and Federal policies on dryland salinity now recognise the need to protect these important natural assets, as well as agricultural land, water resources and urban infrastructure. In addition to salinisation arising from land use change, it is also probable that there may be further impacts caused by climate change, although these are not clear at this stage.

Unfortunately, knowledge of groundwater and surface water interactions with native vegetation has lagged behind understanding of the other impacts of salinity. Fortunately, there is scope to better understand these responses by studying how naturally salt and waterlogging tolerant vegetation survive successfully, and this can provide an indication of the way forward. Over the last 10 years, there have been a number of laboratory, lysimeter, field and modelling studies to investigate the interaction between soil, vegetation, groundwater and salt in areas of shallow saline groundwater. These include a range of vegetation types and environmental conditions (soils, groundwater and climate). Such studies have only been made possible because of recent developments in technology; for example heat pulse techniques to study water use of trees. The studies have shown a variety of vegetation responses to changes in their saline environment. This variable response is explicable and even predictable on the basis of an understanding of common soil and vegetation processes operating across a wide range of vegetation and environmental conditions.

Objectives Increasingly, natural resource managers are expected to protect areas of native vegetation that are affected by shallow saline groundwater.

The aim of these guidelines is to incorporate the recent understanding described above in a form that is useful for natural resource managers so that they can better predict likely vegetation responses to a range of management options.

In these guidelines the term natural resource managers refers to those involved in technical investigations (i.e. botanists, ecologists, hydrogeologists, hydrologists), those responsible for on-ground management of native vegetation, and those setting policy directions for the protection of native vegetation.


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Scope

These guidelines are targeted at native terrestrial vegetation communities that are subject to occasional inundation and increasing salinisation due to groundwater rise.

The term native vegetation in these guidelines refers to vegetation that is indigenous to the area in which it is growing, and does not include areas of re-vegetation or forestry. As these guidelines are concerned only with terrestrial vegetation, they do not address in-stream or frequently inundated littoral zone vegetation communities. Although introduced species (such as the salt tolerant grasses Agropyron and Puccinellia spp.) are not the target of these guidelines, several have been intensively studied (Bleby et al., 1997) and provide good information on plant responses to salinity and inundation.

The primary vegetation communities of interest are those considered to be of conservation value where technical investigations are warranted.

However, in areas where investigations are not possible, the information provided here may help in making reasonable guesses as to likely vegetation responses to salinisation and management intervention.

These guidelines describe the general issues, processes, investigation techniques and management options for native vegetation communities influenced by shallow saline groundwater. It is important to note they are not a comprehensive prescription of how to address every situation as the site-specific nature of the problem renders this impossible. For example, management options in irrigation areas are likely to differ from those in dryland areas.

While policy makers are an audience for these guidelines, it is important to note that the guidelines do not specifically address policy and legislative requirements. Moreover, the guidelines have not received endorsement from any of the jurisdictions they may encompass, and as such represent the views of the authors only.



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Figure 2. Dryland salinity risk in 2050 (NLWRA, 2001) and locations of Ramsar Wetlands of

International Importance (Environment Australia, 1998; http://www.ea.gov.au/water/wetlands/ramsar/index.html)



Audience There is a range of target audiences for these guidelines, each of which may be interested in different aspects and issues of managing native vegetation in saline areas. Summarised below are the potential target audiences and the issues they are likely to face, some of which are addressed in these guidelines, others of which are outside the scope of this document.

Federal and State policy makers • Risks to conservation areas, particularly those of international and national significance • Levels of protection required and the types of intervention possible • Health, threat and rehabilitation indicators (early and late) • Need for engineering options for management

State purchasers of technical information • Possible management options • Necessary investigations and expertise required • On-going monitoring requirements • Planning and implementation of management plans • Need for engineering options for management

State providers of groundwater information • Plant water use characteristics – both amount and source • Plant responses to salinity, waterlogging, and groundwater/surface water regimes • Thresholds for plant health - flooding, leaching, salt removal • Wetland and surface water management • Impacts of irrigation drainage water • Need for engineering options for management

State providers of environmental information/National Parks and Wildlife • General groundwater and salinisation processes • Plant physiology of salinity, waterlogging and flooding • Importance of wetting and drying cycles • Plant community succession • Need for engineering options for management

Catchment, landscape, groundwater, irrigation boards and committees and their salinity and revegetation officers • The importance of the issue for them • Their role in prioritisation, planning and implementation • Salinisation processes, time scales and intervention options • Tradeoffs in water allocation for humans and the environment • Plant breeding and genetics for salt and waterlogging tolerance • Need for engineering options for management

Water corporations, companies and boards • Various information required by the above groups

Consultants • All of the above, and types of investigations and studies required, and methods available

Educators • All of the above

CHAPTER 2. DEFINITION OF THE ISSUES


CHAPTER 2. DEFINITION OF THE ISSUES In this chapter we define the issues associated with the impact of rising saline groundwater on native vegetation by discussing previous studies of relevance, providing some key examples and relating the issues to Federal and State policies and strategies, and Australia’s international obligations.

Previous Studies The implications of salinity for biodiversity conservation and management have been highlighted in a recent report published by the Australian and New Zealand Environment and Conservation Council (ANZECC Taskforce on Salinity and Biodiversity, 2001). This report deals with all aspects of biodiversity (plants, animals and micro-organisms) and highlights the current severity of the problem, the extensiveness of the areas that may be at risk, and the need for integrated programs for salinity management and biodiversity conservation. It also highlights the general lack of significant research on the impacts of salinity on biodiversity. Another important broad-scale study that relates terrestrial vegetation health to shallow groundwater conditions is that of Hatton and Evans (1998). This study deals not only with native terrestrial vegetation, but also with groundwater impacts on in-stream, near-stream, cave, aquifer and wetland ecosystems. While it briefly discusses the detrimental impacts of saline groundwater, it concentrates mostly on the dependence of ecosystems on groundwater (i.e. beneficial effects). This work has recently been followed up in more detail by a project carried out under the National River Health Program (Sinclair Knight Merz, 2001) and has led to the development of a draft groundwater dependent ecosystems policy for New South Wales (Department of Land and Water Conservation, 2002).

The degradation of native vegetation specifically by dryland salinity has received most attention in Western Australia. A summary of the consequences of a changing hydrologic environment for the native vegetation in southwestern Australia is provided by George et al. (1995) and Cramer and Hobbs (2002). The serious loss of biodiversity has led the Western Australian government, in partnership with the community, to commence the development and implementation of recovery plans for threatened species and ecological communities (Blythe et al., 1995; Department of Conservation and Land Management, 2001). One such plan (Toolibin Lake) is described in detail in these guidelines.

For more general discussion on the impacts of land use change on biodiversity and ecosystem function refer to Hobbs (1993), Hobbs et al., (1993) and Hobbs (1998).

Key Examples of Processes, Values and Ecological Importance.

River Murray Floodplain (South Australia)

Recent estimates have identified that approximately 26,000 hectares of the 100,000 hectare floodplain of the lower River Murray is affected by salt, and that this figure is likely to increase to about 40,000 hectares by 2050 and 50,000 hectares by 2100 (Murray-Darling Basin Ministerial Council, 1999).

The floodplain of the lower River Murray contains a variety of wetland types and is one of the eight Wetlands of International Importance listed under the UNESCO Ramsar



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Convention (Environment Australia, 1998) in the Murray-Darling Basin. The Chowilla floodplain in particular is the largest single reserved area of floodplain in this region and is an important wildlife breeding area for key species, including Murray cod (Maccullochella peeli), freckled duck (Stictonetta naevosa) and Murray tortoise (Emydura macquarii).

Extensive field investigations on the Chowilla floodplain have identified raised water table levels and reduced flooding (both caused by river regulation by locks and weirs), as the key drivers in the observed decline in Eucalyptus largiflorens (black box) health across the floodplain. An economic analysis (Sinclair Knight Merz, 1999), performed as part of a feasibility study for the 7,000 hectares of floodplain influenced by the proposed Chowilla Groundwater Control Scheme (Sharley and Huggan, 1995), determined two types of environmental values for the Chowilla floodplain. Use-values, defined as benefits to users of the environment, for example for fishing, hunting, sightseeing, recreation, house-boating and wildlife viewing, were estimated at $187 per hectare. Non-use values, or conservation values, were based on the satisfaction people derive from knowing some aspect of the environment is to be preserved even though they may never visit the area, and were estimated to be $1390 per hectare (Sinclair Knight Merz, 1999). Crudely, this suggests a value of between $5 M and $40 M for the 26,000 hectares of floodplain affected by salinity.

Lower Wimmera River and Terminal Lakes System (Victoria)

The Wimmera River in northwest Victoria normally terminates in Lake Hindmarsh, Victoria's largest body of freshwater (Figure 3). However, in very wet years it may overflow via Outlet Creek into Lakes Albacutya, Brambruck and Agnes and eventually onto the Wirrengren Plain in Wyperfeld National Park. In most years the Wimmera River does not have sufficient flow to replace evaporative losses from Lake Hindmarsh, hence Lake Albacutya fills only intermittently. It last filled in 1974 and has been dry since 1983. Outlet Creek has not flowed to Wirrengren Plain since 1917. Lake Albacutya is a Ramsar listed Wetland of International Importance (Environment Australia, 1998). It is an intermittent brackish to saline lake of 5,731 hectares and has a Eucalyptus camaldulensis (river red gum) woodland fringe with some E. largiflorens and grasslands on the dry bed of the lake. When full, it supports large numbers of waterfowl, including swans, coots and ducks especially large numbers of the rare freckled duck, one of Australia's most endangered wetlands birds. Over 80% of the E. camaldulensis communities in this area (south of Jeparit to the Wirrengren Plain) are visibly affected by dieback and the most likely causes of the dieback are probably rising water tables and salinities, and reduced occurrence of flooding (Wouters, 1993).

Figure 3. Location of the Wimmera River terminal lakes, Western Victoria.



Toolibin Lake (Western Australia)

Toolibin Lake is the last remaining freshwater wetland in the southwest of Western Australia and as such is recognised as a threatened ecological community under a State classification system (non-statutory), and is listed on the Register of the National Estate and under the Ramsar Convention as a Wetland of International Importance due to the high number of breeding waterbird species. The area has extensive stands of Casuarina obesa (swamp sheoak) and associated Melalueca strobophylla and Eucalyptus rudis (flooded gum) communities (Froend et al., 1987). This was the typical vegetation association occurring in wetlands of this area before clearing for agriculture induced rises in groundwater (Halse et al., 1993). The major cause of tree mortality has been attributed to the accumulation of salt in the lake bed sediments due to capillary rise of shallow groundwater and saline surface water inflows (Froend et al., 1987). The lake is important as a breeding area for waterbirds as extensive dense thickets of C. obesa and Melaleuca spp. occur through much of the inundated area. Live vegetation in the lake is important for providing suitable nesting sites and the fresh/brackish water is of sufficiently high quality for growth of emergent vegetation and is suitable for young birds. The periodic drying of the lake also allows persistence of the trees growing in it (Northern Arthur River Wetlands Committee, 1987). As one of the recovery catchments for natural diversity, under the Western Australian Salinity Action Plan, the State government provides additional resources for its management (State Salinity Council, 2000a).

Relationship to Existing Federal and State Policies Recognition of the importance of protecting the natural environment is a feature of much Federal, State and Territory legislation and policy. While few specifically address the impacts of salinisation on native vegetation (with the notable exception of (WA Department of Conservation and Land Management, 2001), many recognise the value of native vegetation for biodiversity, and emphasize management and protection of remaining areas.

At the Federal level, Australia has a number of international obligations in relation to World Heritage properties, the RAMSAR Convention on Wetlands (Ramsar, 1971), the JAMBA (JAMBA, 1981) and CAMBA (CAMBA, 1988). Treaties for the protection of migratory birds and their environment, and the Bonn Convention on the Conservation of Migratory Species of Wild Animals (CMS, 1983). These obligations are covered by the Environment Protection and Biodiversity Conservation Act 1999 (Environment Australia, 1999). Other important Federal policies and strategies relevant to these guidelines include the AFFA Natural Resource Management policy (AFFA, 1999a), the Murray-Darling Basin Integrated Catchment Management Policy (Murray-Darling Basin Ministerial Council, 2001), Draft Basin Salinity Management Strategy (Murray-Darling Basin Ministerial Council, 2000) and Floodplain Wetlands Management Strategy (Murray-Darling Basin Commission, 1998), the National Action Plan for Salinity and Water Quality (AFFA, 2000), the National Principles for the Provision of Water for Ecosystems (ARMCANZ and ANZECC, 1996), the National Strategy for Ecologically Sustainable Development (AFFA, 1992), and the Council of Australian Governments (COAG) Water Reforms (AFFA, 1999b).

As part of the Dryland Salinity component of the National Land and Water Resources Audit (NLWRA, 2001) all of the States have assessed the extent and impacts of dryland salinity and have reported them as follows: South Australia (Barnett, 2000); Victoria



(Clifton, 2000); New South Wales (Littleboy et al., 2000); Western Australia (Short and McConnell, 2000); Tasmania (Bastick and Walker, 2000); and Queensland (Gordon, 2000). Northern Territory had previously identified areas at risk of dryland salinity (Tickell, 1994; Tickell, 1994a; Tickell, 1994b; Tickell, 1997). A salinity audit of the entire Murray-Darling Basin has also recently been completed (Murray-Darling Basin Ministerial Council, 1999). Most States and Territories also have salinity management strategies, or are in the process of either considering or preparing them. Those available at present include: South Australia (Government of South Australia, 2000a; Government of South Australia, 2000b; Government of South Australia, 2000c); Victoria (Government of Victoria , 2000); New South Wales (New South Wales Government, 2000); and Western Australia (State Salinity Council, 2000a; State Salinity Council, 2000b; Frost et al., 2001).

The States and Territories also have specific legislation, policies and strategies relating to conservation of the natural environment and the management of land and water resources. Some key documents that describe these include: South Australia (Department of Environment and Heritage, 2001); Victoria (Natural Resources and Environment, 2000); New South Wales (Native Vegetation Advisory Council NSW, 1999; Native Vegetation Advisory Council NSW, 2000a; Native Vegetation Advisory Council NSW, 2000b; Department of Land and Water Conservation, 1998; Department of Land and Water Conservation, 1999; Department of Land and Water Conservation, 2000; Department of Land and Water Conservation, 2001a; NSW State Wetland Action Group, 2000); Western Australia (Government of Western Australia, 1999; Department of Conservation and Land Management, 2001; Water and Rivers Commission, 2000a; Water and Rivers Commission, 2000b); Tasmania (Department of Primary Industries, Water and Environment, 2001); and Queensland (Environmental Protection Agency, 1999; Environmental Protection Agency, 2000; Department of Natural Resources and Mines, 2001a; Department of Natural Resources and Mines, 2001b).

part two Processes

CHAPTER 3. GROUNDWATER DISCHARGE


CHAPTER 3. GROUNDWATER DISCHARGE Soil salinisation and consequent vegetation dieback results from discharge of saline groundwater that has risen close to the land surface (usually < 5 m). To understand the salinisation of a specific site and how it may change in the future, determination of the groundwater discharge rates and processes is crucial.

Groundwater discharge information needs to be obtained at a number of levels: the overall catchment, the entire discharge area of the catchment, and at specific sites of interest within a given discharge area.

This chapter briefly discusses investigation of groundwater discharge within this hierarchical framework. For more detailed information on groundwater discharge processes and estimation of rates see Salama (1996) and Martin and Metcalfe (1998). For examples of case studies refer to the Special Edition of Agricultural Water Management (Volume 39, 1999).

Catchment Groundwater rise is caused by increases in recharge in a catchment due to changes in land use from native vegetation to dryland crops or pastures that use less water, or to irrigated agriculture. The pressure from this additional recharge can either be transmitted laterally through the aquifer or vertically, resulting in water tables rise. This increased recharge eventually must discharge from the groundwater system. The discharge will occur where the aquifer cannot transmit the additional recharge, i.e. the aquifer capacity is exceeded. This may occur due to a number of factors: (i) the aquifer becomes more constricted due to thinning or narrowing (e.g. basement highs); (ii) groundwater gradient decreases due to changes in topography e.g. break of slope; and (iii) the permeability of the aquifer decreases e.g. dykes, faults, fining of sediments. In the case, where the recharge greatly exceeds the capacity of the aquifer to transmit the water laterally, the aquifer fills up much like a bathtub. It is this groundwater discharge and the salt that it carries to the land surface and into streams and wetlands that lead to the adverse consequences of salinity (Figure 4). For salinity to occur there needs to be a source of salt, and this is generally the soils and/or the groundwater.

In salinised catchments, salt storage is found to be sufficient to maintain redistribution at damaging concentrations for 100's to 1000's of years. In the absence of a water source, the salt stored in the soil would be immobile and of no significance. The salinity of the groundwater need not be high for land salinisation to occur, as evaporation will concentrate the salts.

Under natural conditions, the groundwater system/soil hydrology responds to naturally varying rainfall such that catchment discharge approximates recharge entering the groundwater system in a dynamic hydrological equilibrium (balance). Increased recharge, resulting from changes in land use, means that catchment discharge must also gradually increase until the system reaches a new dynamic equilibrium where the catchment discharge approximates the new recharge rate. This occurs over decades to tens of thousands of years, and is related to the length of the flow path, permeability of the aquifer and the groundwater gradient (Gilfedder, et al., 2001).



Figure 4. Conceptual diagram of a groundwater system showing increased saline groundwater discharge to the land surface, streams and wetlands resulting from increased recharge

under lands cleared for cropping in the uplands of a catchment. This is one of 15 groundwater flow systems defined by Coran et al. (1998).

The average water table depth will rise to a level where sufficient discharge can occur. In steeper land this can be only a small area with a high discharge density, whereas in flat terrain it can be a large area with a small discharge density (Walker, 2000).

The quantity of discharge has little to do with management of the discharge area; it is largely a groundwater response to recharge.

Discharge Area The spatial distribution of groundwater discharge within a catchment can be extremely complicated. It will generally be focused in lower parts of the landscape where heavy-textured soils are a common feature (Figure 4), or upslope of geological features such as bedrock highs, faults, dykes or other topographical features (Figure 5). It is important to note that groundwater use by vegetation is also a form of discharge. Areas in a catchment with high rates of saline surface groundwater discharge can be relatively easily identified, as they are usually features like salt lakes, springs, seeps, soils with distinctive salt efflorescence, or areas of dying trees or shrubs. Areas where the discharge rates are not sufficiently high to exhibit obvious saturated conditions, but are still significant causes of soil salinity, can often be identified by the presence of salt tolerant vegetation such as Halosarcia spp. (samphire), Maireana spp. (bluebush), Atriplex spp. (saltbush), and various grass species. Good information is available on identifying soil salinity using indicator plant species, for example, the booklet “Salinity Indicator Plants: A Guide to Spotting Soil Salting”, available at http://www.nre.vic.gov.au/.

Intermittent or permanent inundation by surface water is a common feature of discharge areas. Areas of groundwater discharge are very hostile environments being high in salt and often either waterlogged due to inundation or very dry following periods of very low rainfall or lack of flooding. This temporal variability in climatic conditions can cause large fluctuations in water tables beneath discharge areas leading to complex variations in discharge fluxes through time.



Figure 5. Conceptual diagram showing groundwater discharge areas in relation to topography,

geology and groundwater flow systems (Salama, 1996).

Specific Site Investigation of groundwater discharge at a specific site involves field measurements to determine groundwater depth and salinity, soil water status, salinity and texture, and vegetation health (and possibly groundwater use) variations across the site. The details of these measurements are presented in Chapter 6. When carrying out specific field investigations it is important to always keep in mind that plants respond to external factors rather than control them; i.e. by way of water use strategies, adaptation to conditions and stress responses. In general, stress is imposed by long-term trends in drought, reductions in flooding, increased waterlogging and salt accumulation. Stress responses include lowering of leaf water potential, senescence, change in rooting characteristics, leaf drop, osmotic drought effects, storage of salt within the plant, and salt toxicity.

CHAPTER 4. PLANT RESPONSES TO SALINITY, WATERLOGGING AND DROUGHT



Groundwater Use by Vegetation Groundwater discharge through the land surface can occur either by direct seepage and evaporation from the soil surface of water transported upwards by capillary rise, or by groundwater uptake and transpiration by vegetation.

Groundwater uptake is often only at low rates in saline areas (Thorburn, 1996), but can still be an important additional source of water that ensures survival during dry periods.

In areas with low salinity, uptake of groundwater can be significant, leading to lowering of water tables.

There are two main mechanisms of groundwater use by vegetation: (i) direct uptake from the saturated zone below the water table, and (ii) uptake from the capillary fringe, or in the soil profile immediately above where groundwater has moved upwards by capillary rise. The former process is not believed to be common. It is difficult for roots to grow and function under saturated conditions, as oxygen is required for plant respiration. However, there are some species, such as mangroves and some Eucalypts (with the capacity to produce aerenchyma in root tissues) that have the ability to transport oxygen within their roots. For most terrestrial plants, the latter process is the means by which plants utilize groundwater, as both oxygen and water are readily available in this zone.

With the exception of some species of halophytes, most plants exclude much of the salt contained in the groundwater at the surface of their roots. For plants that take water directly from (and below) the water table, salinity builds up in the groundwater itself and, because of the large depths available to the roots and the large storage volume, it generally takes considerable time before salt accumulates to concentrations that significantly affect plant water uptake (see Figure 6).

Conversely, salt quickly accumulates in zones of root extraction in and above the capillary fringe, leading to rapid reduction in use of water from this zone (Vertessy et al., 2002).

The only way in which this process can be reversed is if there is a large addition of water to the soil profile (floods, high rainfall) that leaches the salt downwards to the water table or removes it through run-off and aquifer throughflow.

The combination of groundwater discharge and soil leaching at different sites leads to different patterns of salt accumulation. Plants react in a predictable way to the changed salinity patterns via root dieback, growth and transpiration.



For ecosystems to be stable in such conditions, the pattern of salt accumulation through groundwater discharge must be balanced by salt losses through leaching or run-off. Additionally, for sustainability the vegetation must have suitable plant physiological characteristics to react to and tolerate high salinity and waterlogging (and their changing patterns) and climate variability that leads to extreme conditions.

Thresholds for Salt Accumulation under Vegetation

Critical water table depth

Early studies of salt accumulation in response to shallow water tables defined the simple concept of a critical water table depth, below which upward capillary rise is reduced to an extent that long-term salt accumulation is minimised (Talsma, 1963; Peck, 1978).

A critical water table depth of 2 m has been assumed for most Australian contexts. However, this concept is too simplistic as most areas that are underlain by relatively shallow and saline groundwater actually experience alternating cycles of salt accumulation during dry periods and salt leaching during periods of rainfall or flooding.

Vegetation dieback occurs when this dynamic equilibrium is disturbed by changes in the groundwater and/or surface hydrology, such that the soil profiles accumulate salt in the dry times at rates exceeding what can be leached down again during the infrequent wet periods.

Time scales

Time scales for salt accumulation are important for determining whether leaching events due to inundation from floods or high rainfall occur often enough to prevent salinisation of the soil profile. Once a system is disturbed by land use change, the dynamic equilibrium may significantly change. Three examples illustrating a range of time scales for salt accumulation are presented below.



Figure 6. Patterns of soil salt accumulation in (a) a mangrove tidal flat, (b) Melaleuca halmaturorum on an inter-dunal flat in the Upper South East, S.A., and (c) Eucalyptus largiflorens on the Chowilla floodplain, lower River Murray, S.A. The soil water potential (x axis) is at quasi-steady state over a day in the case of a mangrove tidal flat (a). It changes throughout a 12-month period in the case of the inter-dunal flats of the Upper South East (b) , and over a 20-year period in the case of the Chowilla floodplain (c). In the case of the mangroves salt accumulation is a top-down process but is balanced by upward diffusion. For M. halmaturorum on inter-dunal flats salt accumulation is also a top-down process, whereas it is a bottom-up process for E. largiflorens on the River Murray floodplains. (Solid arrows represent upward movement of salt by groundwater discharge, hollow arrows represent downward leaching of salt.

Mangroves (various Avicennia, Aegiceras, Rhizophora and other species) typically grow in saline coastal flats and experience daily inundation of seawater due to tidal movements. This frequent and regular pattern of inundation of saline seawater results in a quasi-steady state salt profile (Fig 6a) whereby salt movement into the soil by convection is balanced by the diffusion of the concentrated salt back to the soil surface. These continual high salt concentrations in the soil mean that mangroves transpire at only a small fraction (< 15%) of the potential evaporation rate (Passioura et al., 1992). This is an example of a natural system that still maintains a dynamic equilibrium.

Melaleuca halmaturorum (swamp paper bark) communities in the Upper South East region of South Australia are the dominant species of the inter-dunal flats that are natural groundwater discharge areas in this region. The flats are flooded in winter and the resultant recharge causes water tables to rise to the surface. The vegetation uses groundwater that has risen to the soil surface at the end of winter. As salt accumulates at high concentrations towards the end of summer the surficial roots die and the tree roots extract water from below the saline zone at the soil surface. At the start of winter salt is leached to the water table by rainfall. Consequently, the water table quickly recharges causing the moderately saline groundwater to rise to the soil

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surface. The leaching of the soil profile with the winter rainfall and flooding is a key component of the survival of these communities (PPK Environment and Infrastructure and CSIRO Land and Water, 1997). The process of salt accumulation and then leaching over a 12-month period is shown in Figure 6b. This is an example of a moderately disturbed system that, while undergoing some change, still maintains some semblance of a dynamic equilibrium”.

Eucalyptus largiflorens (black box) forests and woodlands comprise the dominant vegetation communities of the floodplains of the lower River Murray. Under natural conditions saline water tables beneath the floodplains were deeper (generally > 4m), and large floods occurred much more frequently (1 in 3 years), than under present conditions. Whilst salt accumulation due to groundwater discharge by vegetation occurred naturally under these conditions, leaching from the relatively frequent flooding resulted in soil salinity profiles that did not affect the health of the salt and drought tolerant vegetation over the long-term. The lower frequency of larger floods, together with raised groundwater levels (from building of locks and weirs for river regulation), has led to a change in the balance between leaching during floods and salt accumulation by vegetative discharge. This balance has shifted about an order of magnitude towards salt accumulation with resultant vegetation death (Walker et al., 1994). Measurements suggest a time for salinisation of the soil profile of about 15-20 years for a water table depth of 4 m and clay content of 30% (Figure 6c). This is an example of a greatly disturbed system in which the dynamic equilibrium no longer exists.

From these examples and results from other studies, it is clear that the time scales for soil salinisation vary widely and the processes leading to salt accumulation can be very complex.

Factors such as the depth and salinity of the groundwater, climatic conditions, soil texture, plant water use and salt tolerance characteristics, and the frequency of significant leaching events govern long-term salt accumulation.

All of these factors together control the maintenance of a “salt balance” in the soil. Of these processes the hydrological factors, depth and salinity of groundwater and leaching frequency, are the most disturbed by land use change.

Plant Physiological Responses For plants, a saline environment is defined as one in which there is a high concentration of soluble salts in the soil where plants are growing (Flowers and Yeo, 1986).

This leads to a two-phase response in most plants (Figure 7): (i) firstly, a reduction in the plant water availability due to osmotic effects, leading to water deficit and stress; and then (ii) ion imbalance or toxicity, ultimately leading to death.

Drought and salinity both exert water stress on plant roots and therefore inhibit water uptake. Hence, the processes controlling plant growth in dry soils are similar to those for saline soils (Munns, 1993). When soils are waterlogged, the availability of oxygen to the plant required for root respiration is reduced, thus causing anoxia that



inhibits water use and therefore growth. In addition, nutrient imbalance may also affect waterlogged plants as some ions are more available in these anoxic environments (Ponnamperuma, 1972).

Figure 7. Illustration of the two-phase growth response to salt for three varieties of a given species that differ in salt tolerance: sensitive (S), moderately tolerant (M) and tolerant (T). The varieties differ in the rate at which salt reaches toxic levels in leaves, and hence the rate at which leaves die. The timescale is weeks or months, depending on the level of salinity, and the sensitivity of the species. During Phase 1, the growth rate of all varieties is low because of the osmotic effect of the salt outside the roots: this affects the varieties equally. During Phase 2, leaves in the more sensitive varieties start to die. This exerts an additional effect on growth, and a difference in salt tolerance between varieties develops (Munns, 1993).

Mechanisms of salinity, waterlogging and drought tolerance in plants have been extensively reviewed (e.g. Flowers et al., 1977; Greenway and Munns, 1980; Levitt, 1980; Barrett-Lennard, 1986; Munns, 1993; Allen et al., 1994; Bell, 1999; Niknam and McComb, 2000). In brief, drought and salinity tolerance involves several physiological adaptations to minimise the effects: (i) stomatal control to minimise water loss; (ii) exclusion of salts at the root/soil interface; (iii) salt storage in senescent (dormant) leaves to maintain low ion concentrations in developing leaves; (iv) tissue and/or enzyme tolerance to salinity which allows internal storage of salt; and (v) tolerance to, and recovery from, xylem vessel embolism to allow the exploitation of soils with more negative water potentials. Most drought and salt tolerant species employ several of these mechanisms simultaneously when exposed to highly saline soils. In the case of waterlogging, anoxia impairs the capacity of roots to absorb water and results in stomatal closure, and reductions in water use, mineral absorption and net gas exchange. A common counteracting response to waterlogging with fresh water is the production of adventitious roots just below the water level, thus increasing water use (McEvoy, 1992; Akilan et al., 1997a; Akilan et al., 1997b). It is important to note that waterlogging and salinity can reduce tree and crop growth more than either salinity or waterlogging alone (Barrett-Lennard, 1986; van der Moezel et al., 1988; Marcar, 1993; Allen et al., 1996). For example, it has been demonstrated that species of Eucalyptus with the highest tolerance to waterlogging alone show more

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tolerance to saline waterlogged conditions, and that waterlogging alone is more detrimental than low to moderate salinity (van der Moezel et al., 1991).

Plant responses to these stresses can be typified by threshold values of key environmental parameters such as groundwater depth and salinity, and frequency of inundation.

Threshold values also exist for key plant parameters that govern tolerance to salinity, drought and waterlogging such as minimum pre-dawn and midday leaf water potential, stomatal conductance, and oxygen consumption rate and critical pressure (concentrations).

Leaf water potential and stomatal conductance relate directly to the driest soil water conditions (due to either lack of water per se and/or drought due to the osmotic effects of high salinity) that the plant roots can extract water. Oxygen consumption and critical pressure relates to the ability of the plant to survive periods of anoxia due to waterlogging. Often these thresholds act in combination, an example of which is taken from the study of Jolly et al. (1994), and is shown in Figure 8. The health of black box trees at sites on the Chowilla floodplain of the lower River Murray is declining due to the impacts of river regulation. In this case there is a composite threshold that separates those sites in good health from those suffering health decline. This composite threshold is referred to as the “balance line” and is comprised of a combination of the water table depth and a factor related to the frequency of flooding.

Figure 8. Effects of environmental factors on Eucalyptus lariflorens (black box) health (0=dead to 5=healthy). The balance line is from theory in Jolly (1993) W is the proportion of time the site is undundated and n is a parameter related to soil texture, and in this case has

a value of 3 (loamy clay) (Jolly, 1993).

Generalised Responses of Australian Native Vegetation to Salinity and Waterlogging Most of our knowledge on the salinity and waterlogging tolerance of native Australian species is derived from laboratory and glasshouse studies. One of the problems in utilizing and comparing data from these studies is the lack of uniformity in the

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treatments tested (differing salinity levels, lengths of waterlogging, study durations, response measurements etc.). Moreover, in recent times it has become clear that these types of studies, in which the salinity, irrigation, nutrition and energy are generally kept constant or are closely controlled, are often not representative of the highly variable conditions experienced in the field. Furthermore, the majority of these studies use individual juvenile plants (up to 1 year old), and so the observed responses are unlikely to be representative of mature communities of plants. Unfortunately field data are not available for most species.

The studies that have been carried out to date are too numerous to list here, however a number of comprehensive summaries and reviews have been published that provide useful reference material (Marcar et al., 1995; Marcar et al., 1999; Bell, 1999; Marcar et al., 2000; Niknam and McComb, 2000). The latter paper highlights the disparities in salinity tolerance determined in the glasshouse compared to that measured in the field. Whilst recognizing the shortcomings of the laboratory and glasshouse studies it is still useful to compare the relative salt and waterlogging tolerance of the major Australian native tree species and this was carried out by (Bell, 1999) and is reproduced in Table 1.

It can be concluded from these data that as a general rule of thumb Eucalyptus is generally more tolerant of waterlogging and salinity than Acacia, but less tolerant than Melaleuca and Casuarina. There are of course exceptions to this generalisation.

While the data presented in Table 1 provide some guidance, it should be emphasised that there is a clear need to carry out a great deal more detailed field-based investigations of key vegetation communities. These study areas should be chosen to provide information on species that are widely distributed in areas threatened by salinity, but for which little field-based information currently exists.

Further field-based studies are extremely important as much of our understanding of vegetation responses to salinity in the field situation comes from studies of a handful of species, in a small number of locations.

These future studies should also be targeted to include sites where health decline is thought to be due to a combination of the effects of salinity, waterlogging and drought, as these interactions are still poorly understood in the field context.

While clonal varieties of native species (e.g. E. camaldulensis), and non-native species such as the salt tolerant grasses Agropyron and Puccinellia spp., are not the focus of these guidelines, several have been intensively studied in the field, and provide good information on plant responses to salinity and inundation (Akilan et al., 1997a; Jarwal et al., 1996; Bleby et al., 1997). Lambert and Turner (2000) provide a good summary of the salinity tolerances of native and clonal varieties from a plantation forestry viewpoint.

The tolerance of native Australian species to drought is less studied than that of salinity and waterlogging effects. Much of the work has been on a small range of Eucalyptus species and has tended to be site or region specific. As such, to our knowledge there have been no attempts to generalise the responses and so reference should be made to the individual studies; key ones include Pook et al. (1966);



Landsberg and Wylie (1983); Myers and Neales (1984); Carbon et al. (1981); Colquhoun et al. (1984); Crombie et al. (1988); and Davidson and Reid, (1989).

Table 1. Relative salt/waterlogging tolerance* levels of Australian tree species from a range of

published sources (Bell, 1999).

Note: seawater is approximately 30,000 mg/L NaCl

Very highly tolerant (tolerates waterlogging with 12,000 mg/L NaCl) Casuarina equisetifolia1,9 M. glomerata1

C. glauca1,6,9,11 M. halmaturorum1,11

C. obesa1,9 M. lanceolata11

Melaleuca acuminata1 M. lateriflora1

M. bracteata6 M. leucadendra5,11

M. aff. calycina10 M. subtrigona10

M. cardiophylla10 M. squarrosa11

M. cuticularis11 M. styphelioides11

M. cymbifolia10 M. thyoides1,10

M. decussata11 M. uncinata11

M. eleuterostachya1 Highly tolerant (tolerates 9,000 mg/L NaCl)

Acacia stenophylla1,11 E. sargentii1,7,8,11

Casuarina crista5,9,11 E. spathulata1,7,8,11

Eucalyptus camaldulensis1,2,5,6,8,11 E. intertexta1

E. campaspe11 E. microtheca1

E. cladocalyx var. nana 7,8 E. raveretiana1,6

E. halophila10 E. striaticalyx1

E. kondininensis11 E. tereticornis1,6

E. occidentalis1,8,10,11 Moderately tolerant (tolerates 6,000 mg/L NaCl)

Acacia ampliceps11 E. leptocalyx10

A. aff. lineolata4 E. leucoxylon8

A. auriculiformis5 E. maculata2

A. mutabilis subsp. stipulifera4 E. moluccana2,6

A. salicina11 E. ovata11

Casuarina cunninghamiana5,6,9,11 E. patens8

Eucalyptus aggregata11 E. platypus var. heterophylla7,8

E. argophloia2 E. redunca8

E. camphora11 E. robusta2,6,8,11

E. cladocalyx8 E. rudis11

E. drepanophylla2 E. tereticornis11

E. floctoniae8 E. uncinata10

E. goniantha10 E. wandoo8

Mildly tolerant (tolerates 3,000 mg/L NaCl) Acacia cyclops4,11 E. melliodora6

A. brumalis4 E. paniculata2

A. patagiata4 E. pellita2

A. redolens4 E. urophylla2

Eucalyptus angulosa10 Grevillea robusta2

E. citriodora2 Melaleuca quinquinervia5,11

E. grandis2,6 Mostly intolerant (intolerant of 3,000 mg/L NaCl)

Acacia aulacocarpa5 E. polycarpa2

Casuarina decaisneana3 E. saligna2

Eucalyptus cloeziana2 Lophostemon confertus2

E. intermedia2,6 Pinus caribaea var. hondurensis2

E. pilularis2

1(van der Moezel and Bell, 1990); 2(Sun and Dickinson, 1993); 3(Clemens et al., 1983); 4(Craig et al., 1990); 5(Sun and Dickinson, 1995a); 6(Dunn et al., 1994); 7(Greenwood et al., 1994); 8(Greenwood et al., 1995); 9(van der Moezel et al., 1989); 10(van der Moezel and Bell, 1987); 11(Marcaret al., 1995).

*It is important to note that tolerance levels relate to salt and waterlogging. Further information regarding the salinity tolerance of native shrub and grass species, can be found at various sources including the web address on page 14 and at http://www.agric.wa.gov.au/environment/land/salinity/measurement/Plant_salt_tolerance.htm



Impacts of Climate Variability

Climate variability is often an important determinant in the growth and long-term survival of vegetation in areas undergoing salinisation. While vegetation health may slowly be declining in these areas, it is often sustained periods of drought or lack of flooding that result in significant dieback. Conversely, extended periods of inundation can also cause dieback of vegetation.

Conversely, extreme rainfall and flooding events can often revitalise vegetation communities under salinity stress through leaching of salt from soil profiles and increased plant water availability. Therefore, plant sustainability in saline areas is controlled more by the extreme climatic conditions than the generally prevailing climate. The plant water use strategy must be such that the vegetation survives the long dry periods often at the expense of growth. On the other hand, very wet periods can provide much needed leaching as well as a plentiful supply of water for a short time. A good example of the beneficial impacts of a wet period is the partial recovery of one of the black box communities on the Chowilla floodplain. Slavich et al. (1999b) modelled the growth of a black box community currently in very poor health for the period 1970 to 1994 using a soil-vegetation-atmosphere transfer model (WAVES; Zhang and Dawes, 1998) calibrated with field data from that site. They found that the large, long duration floods of 1974-76 led to greatly improved tree growth in subsequent years by significant leaching of salt from the soil zone. The peak in improved tree growth occurred 12 years after the floods but declined thereafter as the soil salinities in the root zone slowly increased again, resulting in a gradual decline in root zone water availability (Figure 9).

Figure 9. Modeled root zone water availability and canopy leaf growth (as leaf area index) of a Eucalytpus lariflorens (black box) community on the Chowilla floodplain for the

period 1970-94. (Slavich et al., 1999b)

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CHAPTER 5. CASE STUDIES


CHAPTER 5. CASE STUDIES In this chapter we present several case studies that illustrate the range of impacts of salinity on native vegetation health. We discuss three of the studies in some detail and provide a short summary of the remainder. In all cases, further information is available in detailed scientific papers and reports, including a special issue of the journal Agricultural Water Management (Volume 39, 1999). The locations of the case studies are shown in Figure 10.

Figure 10. Map showing location of the case study sites.

Eucalyptus largiflorens Communities of the Chowilla Floodplain, Lower River Murray (South Australia) The Chowilla floodplain is located near the border of NSW, SA and Vic (Figure 11). This ~200 km2 area is dominated by a series of anabranch creeks of the River Murray that have been made permanent by the regulation of the river by locks and weirs during the 1920-30’s. The distribution of the terrestrial vegetation in this low rainfall (mean <250 mm yr-1) area is primarily determined by the availability of water and concentration of salt in the soil profile. The floodplain vegetation comprises two dominant eucalypt species, Eucalyptus camaldulensis (river red gum) and Eucalyptus largiflorens (black box). E. largiflorens is more drought and salt tolerant than E. camaldulensis and occupies approximately 40% of the floodplain area. Groundwater beneath the Chowilla floodplain fluctuates between 2 and 4 m of the surface and is influenced by floods (frequency of 2-25 years depending on the floodplain location) and fluctuations in adjacent watercourses. Groundwater salinity (as electrical conductivity, EC) ranges from 10 to 60 dS m-1. The Chowilla floodplain is a natural discharge area (10-40 mm yr-1) for the saline regional groundwater systems. This leads to the permanently flowing anabranch creeks continuously contributing large salt loads to the River Murray, particularly during flood recessions (Walker et al., 1994).



The hydrology of the floodplain has been greatly modified by river regulation, with water table levels much closer to the surface, and large floods much less frequent than under natural conditions. This has led to long-term salt accumulation in the floodplain soils and is the primary cause of vegetation health decline, particularly the E. largiflorens communities (Jolly and Walker, 1996; Margules and Partners et al., 1990) (Figures 12 and 13).

Figure 11. LANDSAT image showing the location of the Chowilla floodplain.

Figure 12. Eucalyptus largiflorens (black box) woodland dieback on the River Murray floodplain,

Chowilla.

Chowilla Study Site

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Poor Black Box

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DIRECTION OF GROUNDWATER FLOW

Mallee

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DIRECTION OF GROUNDWATER FLOW

Figure 13. Groundwater and vegetation health changes on lower River Murray floodplains, pre

and post river regulation, vegetation clearance and irrigation. Note that in the case of the Chowilla floodplain there are no irrigation impacts.

A draft environmental impact statement was prepared in 1988 (National Environmental Consultancy, 1988) which proposed to minimise the salt loads from Chowilla by surface water control of the anabranch system. Public consultation found that the potential for adverse environmental impacts was of high importance, particularly following the inclusion of much of the Chowilla floodplain in the Riverland Wetland of International Importance under the UNESCO Ramsar Convention (Environment Australia, 1998) in 1987. This lead to the initiation of intensive field investigations aimed at determining the nature of the processes controlling black box tree health.

Results from a series of studies indicate that the water use strategies of E. largiflorens were influenced by salinity (Thorburn et al., 1993a). E. largiflorens box was found to be reliant on saline groundwater for transpiration, together with water from the surface soil after rain or floods (Table 2, Thorburn, 1993a; Jolly and Walker, 1996; Akeroyd et al., 1998). Groundwater was usually taken from the capillary fringe but roots were observed below the water table and were also considered to proliferate in the surface soils after flooding and rainfall events (Akeroyd et al., 1998). The sources of water used by the trees, and the extent to which groundwater was used was influenced by site conditions. The sources of water for a tree at a given site did not change rapidly throughout the year as the changes in salinity in the root zone occurred over longer time scales. This was a result of the deeper and more stable water table. The impact of groundwater salinity on tree water use strategies was therefore most obvious from a comparison of sites of differing groundwater salinity, as these produced different patterns of salt accumulation.

The influence of groundwater salinity on tree water use strategies was also most obvious during dry periods. The surface soils were too dry for trees to extract water, and so the only available water source was in the deeper soil zone. Water in this deeper zone was often saline due to the movement of salt from the groundwater up into the soil, producing a front of salt above the groundwater. Trees overlying highly saline groundwater (65 dS m-1) had a limited zone from which they were able to extract



water, and were reliant on the water that could be transported from the groundwater to the top of the salt front. However, at sites with less saline groundwater (35 dS m-1), trees were able to use deeper groundwater, which may have led to a higher rate of groundwater use. The lower limit to soil water extraction (the plant threshold) was determined from the minimum plant water potential. E. largiflorens were able to reach leaf water potentials of -2.5 to -3.5 MPa (Eldridge et al., 1993), permitting the uptake of water at salinities up to ~60 dS m-1 (the equivalent groundwater salinity threshold). Similar measurements on E. camaldulensis on the Chowilla floodplain (Mensforth et al., 1994) showed that they also used saline groundwater some of the time, but were slightly less salt tolerant than E. largiflorens. The minimum leaf water potential measured for E. camaldulensis was –2.6 MPa, which is equivalent to using water with a salinity of ~40 dS m-1.

Table 2. Depth in the soil profile from where water was extracted; percentage of transpired water

that originated from the groundwater; and groundwater discharge fluxes (mm d-1) by E. largiflorens (sites BH, BM and BT) and E. camaldulensis (Site RM) trees in different

seasons (Tables 3 and 4, Thorburn et al., 1993).

BH BM BT RM Summer 1991 Source (m) 1.7-3.3 0.2-0.6 0.2 / 3.0 0.1 / 2.8 % Groundwater 100% 100% 65% (± 18%) 79% (± 8%) Discharge (mm d-1) 0.3 nda nda 1.0 Winter 1991 (a) c (b) c Source 0.2 / 4.0 0.9-1.3 0.2-0.9 0.1 / 4.0 0.3 / 2.4 % Groundwater 44% (± 21%) 100% 100% 51%(± 17%) 58% (± 10%) Discharge 0.13 0.3 0.2 0.1 1.0 Autumn 1992 (a) (b) Source 0.8-1.3 0.3-0.7 0.5-0.6 1.3-3.2 0.3 / 3.2 % Groundwater 100% 100% 100% 100% 76% (±9%) Discharge 0.3 0.2 0.2 2.0 1.5

a not determined, as transpiration measurements were not made b tree water source was a mixture of water from 0.2 m and 0.4 m depth c measurements a and b, groundwater transpiration rates changed twice during a season

The uptake of saline groundwater results in an accumulation of salt above the groundwater table (Thorburn et al., 1993a). As this salt front progressed to the soil surface over time, less groundwater could be used at the more saline sites. The rate at which the salt front moved upwards was found to be influenced by the groundwater salinity, soil hydraulic conductivity and water content, and the proximity of the roots to the groundwater (Thorburn et al., 1995). Major leaching events such as floods were found to be important in maintaining the salt front at a depth that did not adversely affect tree water uptake. Infiltrating flood waters were suggested to push the accumulated salt bulge back down towards the groundwater, hence maintaining the water uptake of the floodplain trees (Thorburn et al., 1995). As described above, regulation of the River Murray has led to rises in the water table beneath the floodplain (greater capillary rise) and to much less frequent flooding (less leaching of salt). This has resulted in long-term salt accumulation in the floodplain soils that reduces water availability and causes decline in vegetation health, and ultimately death. This processes is summarised conceptually in Figure 14.



Figure 14. Long-term salt accumulation mechanism in River Murray floodplain soils.

Melaleuca halmaturorum communities of the Upper South-East (South Australia) Melaleuca halmaturorum (swamp paper bark Figure 15) forms a significant component of the remaining native vegetation communities of the Upper South East region of South Australia (Figure 10). The topography of this regional groundwater discharge area consists of a series of remnant dunes and interdunal flats formed by the retreat of the coastline. M. halmaturorum occurs in the shallow saline (up to 70 dS m-

1) ephemeral swamps on the interdunal flats, which are localised discharge areas. Groundwater depth fluctuates between the soil surface, at the end of winter following recharge by rainfall, and falls to 1-2 m below the soil surface in response to evaporation induced discharge over summer. Local vertical discharge processes dominate regional groundwater discharge, with lateral groundwater flow rates being low.

Figure 15. Melaleuca halmaturorum (swamp paper bark) community near Duck Island, southeast

of Keith, South Australia.

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Mensforth (1996) showed that the transpiration of M. halmaturorum varied seasonally from 0.7-3.4 mm day –1, was limited by salinity, and that the plant water use strategy was responsive to processes of salt accumulation and waterlogging in the root zone. They also found that M. halmaturorum used groundwater for a large proportion of the year as a result of significant capillary up-flow. However, the zone of root water uptake was dependent on a combination of site processes, which dynamically influenced water availability in the unsaturated zone over the year (shown diagrammatically in Figure 16). The M. halmaturorum trees used groundwater from the soil surface at the end of winter in response to groundwater rise and inundation of the soil profile. During summer they used water from deeper in the soil profile in response to salt accumulation in the surface soils. At the end of summer, although there were high salt concentrations near the soil surface the soil was generally moist and roots were extracting water from below the saline zone. Winter rainfall quickly recharged the groundwater, leached salt from the soil profile, and caused the moderately saline groundwater to rise to the soil surface. Waterlogging caused the roots to die back to near the soil surface. Subsequent evapotranspiration then caused the water table to drop quickly. The roots began to grow, drying the soil until the concentration of salts in the soil solution was too high for more water to be extracted. The roots once again began to die back at the soil surface due to the high salinity. This sequence of events occurred over a time period of 12 months.

The ability of M. halmaturorum to not only survive under these conditions but also to utilise saline groundwater was considered to be enhanced by its ability to withstand low leaf water potentials. The extremely low leaf water potentials (<-6 MPa), generated in the leaves of M. halmaturorum were comparable with those of mangroves. The need for even lower potentials appeared to be avoided by having a dynamic root system that grew in response to the falling water table, after dying back in winter due to waterlogging. In addition to these plant salinity tolerance characteristics, environmental characteristics such as annual groundwater fluctuations maintained salinity in the root zone at baseline levels.



Figure 16. Seasonal root activity and depth of water extraction of Melaleuca halmatorurum

(swamp paper bark).

Casuarina obesa and Melaleuca communities of Toolibin Lake (Western Australia) Toolibin Lake is the last remaining freshwater wetland in the southwest of western Australia with extensive stands of Casuarina obesa (swamp sheoak), Melaleuca spp. and Eucalyptus rudis (flooded gum) (Froend et al., 1987). This vegetation association is typical of the naturally occurring wetland vegetation of this area prior to rises in groundwater induced by clearing for agriculture (Halse et al., 1993). The major cause of tree mortality has been attributed to the accumulation of salt in the sediments of the lake bed due to capillary rise of shallow groundwater, and to inundation with saline surface water inflows (Froend et al., 1987).

C. obesa dominates the seasonally inundated bed of the lake (Figure 17) whilst Melaleuca spp. occur on slightly raised sections of the lake floor and E. rudis is found along the margins of the lake, especially to the west were sediments are thinnest, and along inlet drains. Secondary salinisation has had a greater effect on the lake margin species than on those inhabiting the environments of the lake bottom or the uplands region, which are unaffected by inundation. Melaleuca strobopylla and E. rudis have suffered the most from periods of inundation and increasing soil salinity, to the point of widespread mortality. Although the C. obesa have suffered some dieback, the increased salinity has generally still been within its range of tolerance (Environmental Protection Agency, 1999). Measurements of soil salinity and the calculation of percentage inundation from tree elevation and observations of tree vigour and xylem pressure potential response indicated that tree deaths in the Melaleuaca spp. and C. obesa were due to increased levels of salinity. Death and low vigour in E. rudis was attributed to both increasing salinity and prolonged inundation (Froend et al., 1987).



Flood level

Figure 17. Dense Casuarina obesa stands on the floor of Toolibin Lake showing flood level

equivalent to lake outflow level.

Remediation includes short to medium term engineering measures to decrease salinity within the lake and long-term rehabilitation measures within the catchment. The (Toolibin Lake Recovery Team and Toolibin Lake Technical Advisory Group, 1994) recommended the installation of groundwater pumps along the western shoreline in an attempt to lower the water table elevation below the root zone of the emergent vegetation (Figure 18), and the purchase of a 200 m wide band of previously cleared farmland along the western shoreline to be replanted and act as a buffer and natural drawdown zone. To control saline inflows to the lake a 5.5 km diversion channel was constructed to take water from the Northern Arthur River upstream of Toolibin Lake and divert it around the western boundary of the lake, rejoining the river downstream of the outflow from Lake Walbyring (Figure 19). A separator/barrage was constructed at the upstream end of the channel, the gates of which may be opened to allow saline flows down the diversion channel, or closed to direct fresher flow in the lake. In the short to medium term (20-30 years) the engineering solutions have been undertaken to buy time for more sustainable catchment management actions to take effect. Long-term actions predominantly involve broadscale revegetation of key parts of the catchment together with changed farming practices. Modelling by George et al. (2001) predicted that catchment treatments, including revegetation in key parts of the catchment together with a phase farming system, would be ineffectual in saving the lake unless eighty per cent of the recharge area was revegetated. The Lake Toolibin management system was awarded the inaugural National Salinity Prize (sponsored by the Institution of Engineers Australia, the National Action Plan for Salinity and Water Quality and the Murray Darling Basin Commission) in May 2002.



Figure 18. Submersible pump (P11) and observation bores on the bed of the eastern section of

Toolibin Lake, pumping 250 KL day-1 @ 70 dS m-1. Other sections of the lake are more heavily vegetated as in Figure 17.

Figure 19. Location of Toolibin Lake and schematic showing diversion channel, production bores and observation bores.



Other Selected Australian Studies In this section we briefly describe a number of other case studies of relevance. While some are not concerned with native vegetation, the processes observed can still provide valuable insights into vegetation responses to salinity.

Casuarina glauca and Eucalyptus camaldulensis Plantations (Queensland)

Whilst the water use characteristics of E. camaldulensis (river red gum) have been well documented, relatively little is known of the transpiration rates, groundwater use and other water use characteristics of Casuarina glauca (swamp oak). Cramer et al. (1999) carried out a comparative study of the two species at three saline discharge sites in southeast Queensland. They combined measurements of transpiration rates and isotopic identification of water sources to determine groundwater discharge rates for the two species. Whilst both species accessed groundwater and had conservative water use rates (1.3-3 mm day-1 for C. glauca and 1 to 3 mm day-1 for E. camaldulensis), C. glauca showed greater potential than E. camaldulensis to discharge saline groundwater (C. glauca had a maximum groundwater discharge rate of 2.6 mm day-1). C. glauca showed a greater reliance on groundwater as the primary water source which was more likely related to its greater salt tolerance. It was concluded that determining water use alone may give little insight into the ability of tree species to discharge groundwater. Furthermore, for a given transpiration rate, it is the ability of a particular species to utilise saline groundwater which will ultimately determine their effectiveness for groundwater discharge.

Atriplex nummularia Plantations (New South Wales)

Slavich et al. (1999a) studied the water use characteristics of Atriplex nummularia (old man saltbush) at two sites near Wakool in southern New South Wales. Both sites were established over shallow saline water tables at 1-2 m depth and the plants were annually grazed. Measurements were carried out in both dry summer and moist winter conditions. Transpiration of A. nummularia was found to be very low (<0.3 mm day-1) throughout the monitoring period, and was associated with low leaf area, stomatal conductance and xylem water potential. At most times of the year the plants extracted water from the shallow soil zone, except at the end of summer when half of the plant water use was derived from groundwater. Overall, it was concluded that although A. nummularia can establish and grow slowly on highly saline land, its capacity to transpire saline groundwater is small relative to recharge from irrigation and rainfall. As such, these plantations are likely to have little hydrological influence, a conclusion that challenges numerous unsubstantiated claims that Atriplex spp. use large amounts of saline groundwater.

Groundwater Use by Lucerne (New South Wales)

It is widely believed that deep-rooted perennial plants such as lucerne (Medicago sativa) are able to reduce recharge and use shallow groundwater, thus controlling shallow groundwater levels. Zhang et al. (1999) combined lysimeter studies of lucerne water use with WAVES modelling to give a more accurate picture of the relationship between plant water uptake, salt accumulation, groundwater salinity and plant growth. The use of lysimeters allowed for the measurement of upward capillary flow from the



groundwater, salt accumulation in the soil and other components of the water balance that are difficult to measure in the field. The use of lysimeters also made it possible to determine the response of lucerne to a large step increase in groundwater salinity (from 0.1 to 16 dS m-1). By artificially enriching the isotopic concentration of the groundwater it was also possible to determine how much of the upward capillary flow was being used by the plant. The study came to a number of important conclusions. In the presence of a shallow groundwater table, lucerne did not appear to derive much of its water from the water table directly, preferring to use fresher water stored in the soil profile. The size and vigour of the canopy developed decreased with increased salt in the root zone. Root water extraction patterns changed as a result of an increase in salinity of the groundwater, and exaggerated drying at the surface. The processes of drying out of the soil water store caused upward capillary flow of groundwater, and could have a significant impact on groundwater levels in the short term. Upward capillary flow caused salt to be brought into the soil and root zones and this led to a reduction in transpiration, plant growth, and upward flow. If this process had operated without some irrigation, the lucerne crop would not have been sustainable, or there would have been a large reduction in leaf area. While the focus of this study was a perennial pasture plant, many of the observed responses to salinity may have applicability to less salt tolerant native vegetation.

Eucalyptus camaldulensis and E. occidentalis Trial (New South Wales)

A number of studies have suggested that Eucalyptus occidentalis (swampy yate) has good salt tolerance compared with other common Eucalyptus species and is therefore suitable for planting on saline sites. In a comprehensive field study, Benyon et al. (1999) measured growth and water use of 7-year-old E. camaldulensis and 6-year-old E. occidentalis across a salinity gradient on a saline discharge site near Wellington, New South Wales. They found that E. occidentalis performed better than E. camaldulensis on saline soil and exhibited less growth reduction with increasing root zone salinity. A 10% reduction in height growth was observed for E. camaldulensis when the mean root zone salinity was as low as 2 dS m-1, whereas for E. occidentalis it was only evident at ~10 dS m-1. Similar responses to salinity were observed for factors such as stem diameter and crown volume. In all cases, differences in transpiration rates per unit leaf area were small, compared to differences in the average leaf area per tree. Differences in leaf area were more significant, both between E. camaldulensis on non-saline soil and on moderately saline soil, and between both species on moderately saline soil. Most importantly, on moderately saline soil, E. occidentalis had twice the leaf area as E. camaldulensis, and hence used twice the amount of water per tree. Overall, the study confirmed that E. occidentalis had superior salt tolerance than E. camaldulensis in the field situation, but also that both species responded to increased salinity by reducing their water use and hence growth.

Kyabram Plantations (Victoria)

There have been a number of field and modelling studies of tree water use/groundwater interactions at a plantation near Kyabram in northern Victoria (Heuperman et al., 1984; Heuperman, 1995); Feikema et al., 1997; Heuperman, 1999; Silberstein et al., 1999; Feikema, 2000). The mixed Eucalyptus spp. plantation was established in 1976 and was not irrigated, except for the first 7 years. A network of observation bores and piezometers were installed within and outside the plantation in



1982. Between 1982 and 1993, the water table beneath the plantation was lowered by up to ~4 m compared with the adjacent area, but the effect did not extend more than about 40 m from the plantation edge. Furthermore, there was little impact on the piezometric levels in the aquifer beneath the plantation, and so the trees reversed the hydraulic gradient underneath the plantation. This caused the plantation site to become a ‘sub-surface discharge area’, and resulted in a buildup of soil salinity and an increase in groundwater salinity beneath the plantation. Modelling results suggest that as the salt storage in the soil increased there was a gradual decline in tree water use, and the water table began to rise. The results of this study provide an important reminder that unless there is an effective salt removal mechanism (either vertical or lateral leaching), tree growth in areas of shallow saline groundwater will result in salt buildup in soils and groundwater, with detrimental impacts of tree growth and survival.

part three Assessment, monitoring and

management

CHAPTER 6. ASSESSMENT


CHAPTER 6. ASSESSMENT In this chapter we briefly discuss investigations that can be used to assess the health of a native vegetation community and the biophysical (soil, climate, surface water and groundwater) conditions and relationships that have contributed to the current condition. We firstly describe how to plan a groundwater discharge investigation and we then describe in greater detail the techniques suggested. We divide the investigative techniques into those of a scoping nature, where mostly existing data are used for desktop assessments, and more detailed field measurements and numerical modelling studies. The degree to which the more detailed approaches are used will depend on the conservation value of the community concerned and the available resources.

Planning Groundwater Discharge Investigation

Catchment scale

It is important to determine if the catchment is at equilibrium in order to assess whether the area of groundwater discharge is still expanding. Measuring changes in water tables in existing discharge areas is not a good indicator of this due to time lags between increased recharge and discharge, and responses to local hydrologic effects such as flooding. It is best to use hydrographs in recharge areas, where sufficient lengths of records exist. In most cases there are no long-term hydrographic records available and so groundwater flow systems modelling approaches such as that of Dawes et al. (2001), Gilfedder et al. (2001) and George et al. (2001) are the only way to determine the groundwater discharge response to the increased recharge (Figure 20).

Figure 20. Idealised response of the generalised flow systems, Local, Intermediate and Regional, to a step change in a uniform recharge rate (Dawes et al., 2001; Gilfedder et al., 2001).



In terms of catchment management, it is very difficult, without costly engineering, to change the amount and timing of discharge from a catchment, however it may be possible to change the distribution. The three main options for discharge management are: (i) recharge control; (ii) engineering options; and (iii) living with salt. These are discussed briefly in Chapter 7, and in more detail in Walker et al. (1999), Stirzaker et al (2000), and many other publications.

Entire discharge area

Having identified all of the discharge areas in a catchment, it is important to estimate the fluxes of groundwater that must be discharged through them. This involves estimating the mean recharge across all of the areas of the catchment that are clearly not discharge areas. Without any detailed measurements of the recharge beneath the different land uses and soils of the catchment, this will be a very rough estimate, but a worthwhile one to make. Use should be made of the large body of recharge information; Walker et al. (1999), Petheram et al. (2000) and Stirzaker et al. (2000) are good starting points. To estimate the resulting flux of discharge it is simply a matter of rearranging the steady-state groundwater balance equation:

R *Ar = D * Ad to D = R * Ar / Ad (1)_

Where R is the catchment recharge, D is the discharge and Ar and Ad are the areas of recharge and discharge respectively. For example if the recharge areas of a 100 ha catchment total 80 ha and have a mean recharge flux of 30 mm yr-1, then the 20 ha of discharge area must have a discharge flux of 120 mm yr-1.

Specific discharge site

An initial electromagnetic (EM) induction survey along transects will provide an indication of the variability in soil type, salinity and water status and therefore assist in deciding on sampling locations, for piezometer installation, and vegetation and soil sampling. Installation of a limited number of piezometers along these transects, combined with surveying for surface topography, will provide good information on the water table depth variations across the site. Sampling of water from the piezometers will provide information on the groundwater salinity. Soil sampling at a number of depths down the profile when installing the piezometers will enable soil type, salinity and water status variations across the site to also be determined.

Salt accumulation rates along a transect can be estimated from the water table depth, groundwater salinity and soil texture data using empirical relationships (Gardner, 1958; Warrick, 1988; Thorburn et al., 1992), or soil water and solute transport models such as WAVES (Zhang and Dawes, 1998). The latter is more difficult to apply but is more realistic as it enables the impacts of the variability in climate and site inundation to be included. As discussed in Chapter 4, there are varying degrees of dynamism of salt accumulation in discharge areas due to differences in timing of inundation events and rates of upward groundwater flow (Figure 21).



Figure 21. Contrasting examples of the dynamism of salt accumulation in discharge areas. In the case of Melaleuca halmaturorum in the inter-dunal flats of the Upper South East of South Australia, salt regularly accumulates throughout the profile during summer and

autumn and then leaches down again during winter and spring. Alternatively, for Eucalyptus largiflorens on the Chowilla floodplain of the lower River Murray, salt accumulates slowly over a 15 to 20 year period, and is only leached down again by

extreme floods.

Groundwater uptake by vegetation in discharge areas and the resultant rates of salt accumulation in soils can also be estimated using simple analytical models such as that of Thorburn et al. (1995) that do not require vast amounts of data to use. The Thorburn et al. (1995) model is based on root zone salt and water balances and assumes that (i) both water and salt are drawn upwards from the water table in response to plant water extraction in the soil; and that (ii) the uptake of water by the plant concentrates the salt in the soil solution until some threshold salinity is reached, above which the plants can no longer extract the water. The depth at which the threshold salinity is reached is called the salt front. The rate at which groundwater is taken up is controlled by the passage of groundwater through the soil, from the water table to either the salt front or the bottom of the root zone, whichever is closer to the surface. An example of the use of this simple analytical approach to estimate time frames for salt accumulation is shown in Figure 22. This example, taken from Thorburn (1996), models a clay and a loam soil, both of which have a constant water table at 4 m depth and an initially salt free soil. The groundwater salinity is expressed relative to the plant threshold salinity. These simulations demonstrate how the distance over which water must move through the soil to reach the roots increases with time as plants concentrate the salt in the root zone (i.e. the salt front moves upwards over time). This process occurs rapidly in the early times when the soil is relatively salt free, but slows down as the salt concentrations in the soil increase closer to the salinity threshold of the plant. The movement of the salt front is faster if the relative groundwater salinity is lower, because the plants can take up more

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groundwater before their salinity threshold is reached. If a flooding or extreme rainfall event occurs in which salt is leached from the profile, this whole process will start again.

Figure 22. Simulated change in depth of the salt front with time in a clay soil (solid lines) with two different relative salinities, and in a loam soil (dashed line). The two Y scales are

given for convenience. This example is taken from Thorburn (1996), and was simulated using the simple analytical model of Thorburn et al. (1995).

The final step is to relate the salt accumulation rates, climate and inundation conditions to the current vegetation health and assess how it might respond to any given changes in the groundwater regime (water table rises as recharge increases; or falls due to the benefits of management; and/or fluctuates due to variations in climate and inundation).

Scoping Investigations

Initial Site Condition Assessment

An initial visual assessment of the site may provide an indication of past land use and an appraisal of the current condition of the site. Assessment of site disturbance would include a visual estimate of the percentage of regrowth, bare ground, erosion features, poor drainage and compaction as indicated by standing water or patchy plant growth. A percentage estimate of weed cover is also a useful indicator of site disturbance. Other parameters to look for would be damage due to grazing, disease, birds and insects, coppicing, fire and the encroachment of salt tolerant plants. Information on the surrounding area such as land use, proximity to irrigation and its history, particularly date of disturbance should also be collated, even if it is anecdotal in nature.

Distance betw

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Vegetation Mapping and Health Assessment

Mapping of the extent, composition, structure and health of vegetation is essential in order to define the conservation value of a specific community and establish baseline data for evaluation of regeneration or decline.

A good starting point is any existing maps of the area containing vegetation information. The National Land and Water Resources Atlas (http://audit.ea.gov.au/anra/atlas_home.cfm) has land use information Australia-wide. Detailed floristic composition and health of both the understorey and overstorey and community structure are desirable, but it many instances will not be available and so specific surveys will need to be carried out. Floristic composition, classification and structure of vegetation communities are usually mapped using the methods based on those of Beadle and Costin (1952) and Specht, (1970). More recently Heard and Channon (1997) have developed a methodology for surveying native vegetation. For all aspects, use should be made of aerial photography and remotely sensed data wherever possible, as described below. Assessment of vegetation health is usually carried out using visual techniques that are quantified by assigning numerical health indices based on one or more easily observed criteria. The simplest method is that of Lay and Meissner (1985) which uses a health scale of 0 (dead) to 5 (healthy), together with a vigour scale of 0 (dead) to 5 (optimum growth). A more comprehensive method with greater resolution is that based on Grimes (1987) methodology by Eldridge (1993). In this method a score of 1 to 5 is given for each of four criteria (crown size, crown density, dead branches and crown epicormic growth) and the scores summed to provide an overall health scale of 4 to 20. Both methods are described in Appendices 3 and 4.

Airphoto Interpretation

Comparison between historical and modern aerial photographs can provide spatial and temporal information on changes in both the area of vegetation cover and its health.

Photographic interpretation of land features and their changes over time are also possible. This can be very important as vegetation clearance can also cause erosion and sedimentation that in turn may affect the surface drainage network, with consequent impacts on vegetation health. All available photos of the site should be sought in order to build a comprehensive time sequence of events. An example of changes in vegetation health over time is shown in Figure 23 (taken from PPK Environment and Infrastructure, 1998). In this case, historical aerial photography spanning a 54 year period was used to reconstruct the increasing dieback of riparian vegetation on the River Murray floodplain in response to increased saline groundwater inflows resulting from irrigation development.



Figure 23. Use of historical aerial photography to reconstruct the increasing dieback of riparian vegetation on the River Murray floodplain near Lock 4 in response to increased saline

groundwater inflows resulting from irrigation development (PPK, 1998).

Topographic Survey

Ground surface elevation data are essential for determining the nature of the surface drainage network and thereby identifying areas where surface flooding may occur, and the flooding frequency and duration of inundation.

Surface elevations are also required for reducing groundwater data to a common datum so that contouring of groundwater levels can be carried out and flow directions determined. Spatial analysis of both the surface elevations and groundwater contours can also identify areas likely to be prone to waterlogging. Detailed topographic surveys are time consuming, require specialized surveying equipment and are therefore often expensive to carry out. Approximate surveys can be carried out rapidly using hand held global positioning systems, although resolution in both the horizontal and vertical directions is likely to be no better than ~5m. Most Australian States and Territories are presently planning and developing high-resolution Digital Elevation Model (DEM) coverages for their jurisdictions.

Groundwater Depth and Salinity

Measurement of groundwater depths and salinities, both beneath the vegetation communities and across the surrounding region, is essential.

Groundwater depths are measured using piezometers or observation wells. For details on the installation of piezometers and the measurement of their water levels see Hunt and Gilkes (1992), Crossing and Simons (2000) or Henschke (2001). For interpretation of piezometer water level data see hydrogeological texts such as Freeze and Cherry (1979). Groundwater samples for salinity are collected by pumping or bailing from piezometers. It is important to purge the piezometers prior to taking the sample. This involves pumping out stagnant water sitting within the piezometer and sampling the uncontaminated water that then enters the piezometer from the surrounding groundwater. Generally, the equivalent of three times the volume of the

All trees healthy

No irrigation

Irrigation at Loxton

Lock 4

Trees to south unhealthy (due to Loxton irrigation)

Lock 4

Bookpurnong1998

Large areas of unhealthy or dead trees

Further irrigation development

Dead trees

Lock 4

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Irrigation development at Bookpurnong from 1964

Dead trees

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Irrigation at Loxton

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Dead trees

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Irrigation development at Bookpurnong from 1964

Dead trees

Bookpurnong1945

Bookpurnong1972



water standing in the piezometer should be removed prior to sampling, or until the piezometer has dried twice and recovered to 50% (for low yielding piezometers).

EM Survey

Electromagnetic (EM) induction surveys are useful for qualitative site investigations as large areas can be mapped in a rapid and cost effective manner.

EM instruments measure the bulk electrical conductivity of a soil to a defined depth. As the electrical conductivity of a soil is a complex function of soil structure, texture, mineralogy, water content and salt concentration, these surveys are qualitative in nature, but still very useful for site characterisation. However, these instruments can be used quantitatively with calibration of measurements with soil properties (Cook et al., 1992; Bennett et al., 2000). EM can be utilised at a range of scales for both depth and area. The most commonly used ground-based EM devices are those manufactured by Geonics Ltd., which have a range of inter-coil spacings and frequencies (McNeill, 1986). For shallow exploration of soil salinity and texture the EM38 is commonly used as it can cover large areas quickly without ground electrodes (Figure 24). The EM38 penetrates to depths of 1.5 metres and 0.75 metres in the vertical and horizontal dipole modes respectively and reads electrical conductivity directly (Bennett and George, 1995).

Figure 24. Electromagnetic survey using a Geonics Ltd. EM38 across a transect.

The EM31 is a larger instrument that has an effective depth of exploration of about six metres and is used to map deeper soil profiles, geological variations, or any subsurface feature associated with changes in the bulk conductivity. The EM38 and EM31 devices can be mounted onto mobile vehicles (such as quad bikes) to survey larger areas in a more cost-effective way (Martin and Metcalfe, 1998) The EM34 is used for deeper exploration, and has up to 3 inter-coil spacings to give variable depths of exploration down to 60 metres. Further details on these (and other) Geonics Ltd. Instruments can be found at http://www.geonics.com. To cover very large areas (>10,000 ha) and/or to obtain deep profile information an airborne EM survey should be considered. When combined with other geological data, airborne EM (and other



geophysics) can be of use in constructing a conceptual model of the hydrogeology of the site. A summary of the use of airborne geophysics for salinity management can be found in George et al. (1998). For a comprehensive summary of the use of EM methods in salinity investigations refer to Cook and Williams (1998) and Martin and Metcalfe (1998).

Soil Type, Salinity and Water Status Profiles

For quantitative information on the soil type, salinity and water status of a site, field sampling of soil profiles using augering or drilling are necessary.

Hand augering or dry drilling should be carried out to the depth of the water table, with sampling more frequent near the soil surface as this is where salinity and soil water conditions change most rapidly (suggest sampling intervals of ~0.1 m for 0-1 m, ~0.2 m for 1-2 m, and ~0.5 m for > 2m depth). Soils can be described using the standard terminology (McDonald et al., 1990) on the basis of these soil profiles to a depth of 1.5m. Soil from a given sampling interval should be mixed and a sub-sample placed in a 500ml glass jar and sealed with electrical tape. The samples are then analysed for gravimetric water content, chloride concentration of the soil water, and matric and osmotic suction using the methods described in Appendices 1 and 2. Soil salinity can be approximated by measuring the electrical conductivity of a 1:5 soil:water solution (EC1:5) or saturated paste extract (ECe) using methods described in Rayment and Higginson (1992). If desired, particle size distributions of some of the samples can also be measured using the pipette method (Lewis, 1983), to provide information on soil textural changes with depth. A more crude measure of soil texture can be done in the field using the ribbon test as described by McDonald et al. (1990).

The results for each parameter should be plotted up as profiles with depth. Gravimetric water content and matric suction profiles describe the moisture status of the soil. Gravimetric water contents can be used to determine exactly how much water is stored in the profile (in part determined by the soil texture), whereas matric suctions describe how available the water is, irrespective of the soil texture (the higher the matric suction, the drier the soil, and hence the lower the water availability). Chloride and osmotic suction profiles describe the salinity status of the soil. The availability of soil water to plants is governed by a combination of matric suction (how much water is available per se) and osmotic suction (is it of low enough salinity for the plant to extract). The overall plant water availability is determined by the total soil suction (addition of the matric and osmotic suctions). For a plant to be able to extract any water at all from the profile the total soil suction must be less that plant water suction (or if you are using potentials, the negative values of the suctions), the total soil potential has to be greater than the plant water potential.

Examples of these types of data are shown for two sites in Figure 25. In this case the Lignum site generally has higher water contents throughout the soil profile than the Dead Black Box site. This is due primarily to the profile being comprised of a heavier textured soil as the matric suction data show that the profile has less water available (has higher matric suctions), particularly in the surface 1 m, suggesting that this zone is the active root zone for the vegetation and evaporation. The chloride concentrations (and therefore osmotic suctions) under the Lignum site are reasonably low in this zone, but when combined with the matric suctions, the total suctions are



fairly high (4-5 MPa) suggesting that the vegetation may be suffering some water stress at the time of sampling, caused primarily by lack of water per se (although the maximum plant water suction for lignum is ~8 MPa suggesting that the plants may still have been extracting some water). At the Dead Black Box site, the matric suctions in the surface 1 m are slightly lower suggesting minimal plant water extraction, but relatively high rates of evaporation from the soil surface. The chloride and osmotic suction values are extremely high, leading to such high total suctions that there is no water available to most plants. Salinisation of the root zone is the likely cause of tree death at this site.

Other soil physical parameters typically measured include bulk density and permeability (for methods see Rayment and Higginson, 1992). More detailed soil chemical properties include pH, cation exchange capacity, total soluble salts, exchangeable sodium percentage and total organic carbon (for methods refer to Topp et al., 1992).

Figure 25. Water content, chloride, matric, osmotic and total suction profiles from two sites on the Chowilla floodplain in South Australia (McEwan et al., 1991).

Information on Inundation/Flooding

Many sites that undergo salinisation are subject to inundation or flooding.

Floodplains experienced inundation under natural conditions, providing an important supplementary water supply and a means by which accumulated salt could be leached from plant root zones. Therefore, any changes to the flooding regime of these areas are likely to have consequences for vegetation health. Many of Australia’s larger rivers are highly regulated for water supply, which has resulted in a reduction in flood frequency and duration and changes to stream/aquifer interactions. Conversely, clearing of catchments usually results in increased runoff that in turn can lead to the increased incidence of flooding and hence waterlogging, particularly in low-lying areas. Clearing also leads to increasing stream salinities and when these waters

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inundate a site, salt can be added to the soils and groundwater systems. For these reasons it is important to try to establish the inundation regime of a site, both historically and under current conditions. This can be quite difficult due to lack of data, with anecdotal recollections of land managers often the only evidence available. Use should be made of any available historical aerial photography and topographic survey data. In areas subject to regular inundation such as floodplains, satellite data from multiple times can be used to construct maps of areas inundated at different river flows. An example of the use of LANDSAT Thematic Mapper and Multi-Spectral Scanner data for flood mapping is shown in Figure 26, where the extent of two different size floods on the Chowilla floodplain is shown. As described by Overton et al. (1999), multiple satellite images can be combined with hydrological modelling and Geographical Information Systems (GIS) to predict areas which are inundated at any given river flow.

Figure 26. Map of the Chowilla floodplain showing the extent of inundation of two floods of

contrasting size and return period. Satelite imagery used to construct these maps was analysed by P. Hutton and R. Fisher of CSIRO Division of Water Resources.

Climate

Long-term rainfall and evaporation records are essential for understanding the climatic context in which the decline in health of a vegetation community has occurred.

Drought alone can be an important determinant of vegetation health, as well as exacerbating problems caused by salinity and/or waterlogging. Long-term rainfall



records can also assist in identifying any correlation with groundwater depth changes such as large episodic rainfall events, and seasonal variation, as described above. Long-term climatic records are available for many stations from the Bureau of Meteorology (http://www.bom.gov.au/), or in software packages such as: MetAccess (http://www.hzn.com.au/metacces.htm); Rainman (http://www.dpi.qld.gov.au/qcca/4781.html); and SILO (http://www.dnr.qld.gov.au/resourcenet/silo/index.html).

Detailed Measurements

Plant Measurements

A number of detailed field measurements can be made to determine plant stress (leaf area, leaf water potential, stomatal conductance), and water use (heat pulse) and source(s) (stable isotopes of water).

Plant Water Stress: Plants that are under water stress need to lower their leaf potentials to enable their roots to absorb water at the low water potentials that exist in the soil. The rate at which water is lost to the atmosphere through leaf (and stem) stomata is governed by the stomatal conductance. When plants are under stress they generally try to limit water loss by closing their stomata, thereby reducing the stomatal conductance. Another means of limiting water loss is leaf drop, so measurements of leaf area over time can also help identify increasing stress. Leaf water potential is most commonly measured with a pressure chamber known as the Scholander bomb (Scholander et al., 1965). The apparatus consists of a pressure chamber in which a twig with several leaves (or a single leaf), is placed, with the twig (or petiole), protruding through an aperture in the chamber lid which is sealed with a rubber washer. Pressure is added to the chamber from a nitrogen gas source, until water in the xylem first appears at the cut surface of the twig/petiole. This point represents the pressure that is needed to balance the tension that was in the xylem vessels when the twig/leaf was cut. Providing equilibrium is achieved, the xylem water potential will be equal to the water potential of the source water at the depth(s) of plant water uptake. The trees/twigs are sampled prior to sunrise, when it is assumed that the plants have equilibrated overnight with the soil or groundwater, and again at midday. Plant water potential can also be measured directly using a thermocouple psychrometer (Turner, 1981). Minimum leaf water potentials observed for species such as E. camaldulensis (Mensforth et al., 1994), E. Largiflorens (Zubrunich, 1996), M. halmaturorum (Mensforth, 1996) are –2.5 MPa, -4.0 MPa and –12.0 MPa respectively. Stomatal conductance is usually measured with a diffusion porometer such as the Licor 1600 or Delta-T AP4. Measurement of leaf area is most easily carried out using the Adelaide module method (Andrew et al., 1979). This involves removing a branchlet and counting the equivalent number of modules on the tree. The leaf area of the module is then scaled up to the whole tree.

Water Use: Plant water use can be estimated from sap flow velocity using the heat pulse technique (Swanson and Whitfield, 1981). This method uses heat as a tracer of sap velocity. In brief, a heater probe and two temperature sensors are inserted into the sapwood (conducting tissue) of a tree and a short (<1 second) pulse of heat is released from the heater. The temperature sensors are located at fixed distances above (10 mm) and below (5 mm) the heater and their measurement of the heat dissipation



allows separation of the convective and diffusive components of the pulse. The convection flux is used to derive the sap flux. Continuous measurements of sap velocity at regular intervals are converted to daily tree transpiration (L tree-1 day-1) using the methods of Hatton et al. (1990). Transpiration on an areal basis can be estimated from the daily tree data by scaling on conducting wood area thus:

Transpiration (mm day-1) = Tree transpiration (L day-1) x plot conducting wood area (cm2) (2) Tree conducting wood area (cm2) x plot area (m2)

For examples of the use of the heat pulse technique in this way see Jolly and Walker (1996) and Thorburn et al. (1993a).

Water Source(s): Measurement of the stable isotopes of water (2H and 18O) provides a means of determining from where plants acquire their water. In principle the process is simple, matching the isotope concentration of water transpired (i.e. water in the conducting tissues of plants), with the possible water sources that the plants may be accessing (groundwater, stream water, shallow or deep soil water; Figure 27).

Figure 27. Potential plant water sources, soil water, groundwater, rain, and twig isotopic content in per mille deuterium.

The isotope data can be used in conjunction with soil water potential data to help infer the depth of extraction from soils. The basis for the stable isotope technique is that different waters will have varying isotopic signatures caused by their history of condensation and evaporation. The isotopic composition of twigs (not leaves as leaf water is evaporatively enriched due to transpiration) has been found to be consistent with the water extracted by roots and transported through the sapwood. It is therefore possible to sample the twigs causing minimal destruction to the plant and also allowing for mixing to take place in the trunk. This technique has been validated for several native species in field situations including Eucalyptus spp. (Thorburn et al., 1993b; Mensforth et al., 1994; Kennett-Smith et al., 1993), Melaleuca spp. (Mensforth, 1996), Atriplex spp. (Slavich et al., 1999a) and Casuarina spp. (Cramer



et al., 1999). Xylem water is extracted from the twig material by azeotropic distillation (Revesz and Woods, 1990). The 2H and 18O concentrations of the potential source waters and the water extracted from the plant material are determined by mass spectrometry. It is important to point out that there are potential sources of error with the method and users are referred to Walker et al. (2001a) and Walker et al. (2001b) for a complete description and discussion of the methodology.

Groundwater Discharge Estimation

In addition to use by vegetation, groundwater can also discharge as evaporation at the soil surface. If the groundwater is saline to any degree, significant salt accumulation may result, particularly in topographically lower regions that have shallow water tables (salt lakes are natural examples of evaporative groundwater discharge). As water table levels rise in catchments, evaporative discharge can become a significant component of the groundwater balance and therefore requires quantification. The rate of evaporative discharge is highly dependent on groundwater depth and the soil physical properties of the zone between the water table and the surface. The maximum (i.e. soil-limited) steady upward evaporative discharge flux (qm) that can be sustained from a water table, at a depth d, is given by (Gardner, 1958; Warrick, 1988; Thorburn et al., 1992).

qm = A d-n (3)

where A and n are constants dependent on the soil texture. Direct measurement of evaporative discharge is generally difficult due to problems in obtaining accurate values for the soil parameters A and n, and so the discharge rates are more commonly inferred using soil profiles of environmental tracers such as chloride or the stable isotopes of water (Barnes et al., 1989; Salama, 1996). Typical discharge rates from bare soils in agricultural areas with water tables at approximately 1 m depth range from 1-10 mm day-1, and in bare salt flats the rate is of the order of 0.01-0.1mm day-1 (Thorburn et al., 1992).

Remote-Sensing Vegetation Survey

Remotely sensed satellite data can be useful in mapping vegetation and its changes as imagery can be obtained for the same location at multiple times. For example, LANDSAT Thematic Mapper satellite data have been collected over all of Australia on a 16-day cycle since 1983 and have a pixel size of 30 m. Similarly, LANDSAT Multi-Spectral Scanner data with a pixel size of 80 m have been collected since 1972. These satellites provide data in the visible, infrared, and thermal infrared portions of the electromagnetic spectrum. For example, Overton et al. (1994) used a combination of LANDSAT 5 Thematic Mapper and digital orthophotography to map riparian vegetation in an area of the Chowilla floodplain (Figure 28). In later work, Overton et al. (1996) mapped changes in vegetation on the Chowilla floodplain between 1988 and 1995 by analysing changes in the normalised difference vegetation index (NDVI) derived from the LANDSAT 5 imagery (Figure 29). NDVI is a measure of vegetation greenness and so changes in NDVI over time can indicate areas of vegetation experiencing increasing (or decreasing) stress.



Vegetation of Monoman IslandChowilla Anabranch Region, South Australia

Water

Bare GroundGrassland

Chenopods

Dune

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Black Box Closed WoodlandBlack Box Open Woodland / Lignum

River Red Gum ForestMallee

Metres

0 300

Figure 28. Map of riparian vegetation in an area of Chowilla floodplain constructed using LANDSAT 5 Thematic Mapper and digital orthophotography (Overton et al., 1994).

Chowilla FloodplainVegetation Change

Landsat TM Band 1Difference

DN(1988) - DN(1994)

1988-1994

Increase

Decrease

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Figure 29. Changes in Chowilla floodplain vegetation determined from NDVI changes derived from LANDSAT 5 Thematic Mapper imagery (Overton et al., 1996).



Vegetation Growth Modelling

Computer models of vegetation responses to salinity and water availability can be valuable tools in understanding the processes of vegetation health decline. Furthermore, they can be a valuable aid for testing the likely improvements in vegetation health in response to management changes such as lowering of water tables and manipulation of surface water inundation regimes. A particularly useful tool for this purpose is WAVES (Zhang and Dawes, 1998), an integrated one-dimensional unsaturated zone model that simulates energy, water, carbon, and solute balances of the soil-vegetation-atmosphere system on a daily time step. It also includes water and solute interactions between the soil zone and underlying groundwater. WAVES predicts the dynamic interactions and feedbacks between processes and hence is well suited to investigations of vegetation growth response to climate and transient soil water and salinity status. The model consists of four modules that simulate the energy, water, carbon (plant growth), and solute (salt) balances (Figure 30).

Figure 30. Conceptual diagram showing the major processes modelled by WAVES (Zhang and Dawes, 1998).

A good example of the use of WAVES to investigate the processes of vegetation dieback due to soil salinisation is the study of Slavich et al. (1999b). Field studies over several years were used to calibrate the model for Eucalyptus largiflorens at a number of sites experiencing varying degrees of soil salinisation on the Chowilla floodplain. The model was then used to carry out an historical reconstruction of the vegetation response to increasing soil salinisation over the period 1970-1994. For an example of the predictions for one of the sites refer to Figure 9. In this case, the model showed that there was a large increase in water availability (due to leaching of salt from the soil profile) following the long floods of 1974-76 and this led to improvements in vegetation growth (indicated by increased leaf area index) for 12 years after these major floods. However, the lack of any flooding for another 18 years resulted in salt accumulation in the soils that reached a critical level in 1987 in which water availability had reduced to a level where the vegetation began to dieback. The model was then used to predict improvements in vegetation health that may arise from various combinations of water table lowering and increased flooding.

Runoff InfiltrationSoil Layer 1

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CHAPTER 7. MANAGEMENT


CHAPTER 7. MANAGEMENT In this chapter we discuss some of the considerations when designing management plans for threatened vegetation communities. They are not intended in any way to be prescriptive, as every situation is different, as are the aspirations and resources of the custodians and other stakeholders of a vegetation community. We only briefly describe some of the management options as most are discussed in greater detail elsewhere. Good general sources of information concerning ecological restoration include Hobbs and Norton (1996) and Hobbs and Harris (2001). The following websites contain general information on the management of salinity:

National Dryland Salinity Program, http://www.ndsp.gov.au Australian Natural Resources Atlas, http://audit.ea.gov.au/ANRA/atlas_home.cfm Salinity, Western Australia, http://www.agric.wa.gov.au/environment/land/salinity

Goal Setting While seemingly obvious, this is the most important step in the management process. With very few exceptions, it will not be possible to completely restore a native vegetation community back to its natural condition. Cramer and Hobbs (2002) highlight the need to set priorities for the protection and restoration of native vegetation at risk based on an assessment of relative threat and probability of persistence or recovery. It is therefore important to clearly identify what is achievable for a given situation. Management goals can be summarised into three main categories: (i) recovery of the ecosystem; (ii) containment of further impacts; and (iii) adaptation to the new salinity regime. The decision will be based on the financial and technical resources available, ecological significance of the area and its current health, stakeholder aspirations, and other considerations. In most instances tradeoffs will be needed (Figure 31).

The overall aim of the plan is to manage the vegetation community to meet an environmental outcome agreed to by all stakeholders.

Blythe et al. (1995) and George et al. (1995) provide guidance and case study examples for the management of native vegetation affected or threatened by salinity.

Figure 31. Example of some of the trade off decisions that will need to be made when setting realistic goals for the management of an affected or threatened native vegetation

community.

Recovery, Containment, Adaptation

Judgements

Current health

Environmental value

Capital and on-going costs of restoration

Stakeholder aspirationsand expectations

Future catchment salinity regime

Hydrology and hydrogeology

Others?

Recovery, Containment, Adaptation

Judgements

Current health

Environmental value

Capital and on-going costs of restoration

Stakeholder aspirationsand expectations

Future catchment salinity regime

Hydrology and hydrogeology

Others?



Considerations in Selecting an Appropriate Option The hydrology and hydrogeology of the catchment will in part define the management options available, along with the characteristics of the plant community itself. It is therefore important to obtain as good an understanding of these as possible prior to selecting a management option. For the site itself, there is a need to determine salt balances in the soil and shallow groundwater and how they may change under different managements options. This is important, as the possibility for salt removal will be an important determinant of the most appropriate option. In general terms the main options for dealing with salinity, all of which can be used in combination, are:

Recharge control: This involves changing land use practices within a catchment so that much more of the rainfall is used by the crops, pastures and other vegetation, and hence recharge beneath these land uses is significantly reduced. Using rainfall where it falls with high water use species is the goal of this option. However, to date no agricultural cropping/grazing systems have been shown to have recharge rates as low as those under native vegetation; only tree plantations exhibit anything like the natural recharge regime. While recharge control is clearly desirable and will in the long-term reduce the volumes of groundwater that will need to be discharged, in nearly all cases there will continue to be significant areas of groundwater discharge (which may also continue to expand) that pose a threat to native vegetation. Identification of these areas and their likely expansion is an important component of a management plan.

Engineering options: In situations where recharge control can not reduce discharge, at least in the short-term, groundwater control options such as drains and bores can be used to protect key environmental (and other) assets. These can be effective in reducing groundwater levels and removing salt in discharge areas but have the downside that they are expensive to install and maintain, and need some form of disposal for the saline groundwater extracted. In some States it is not permissible to dispose of saline water into streams, irrespective of whether they are already saline or not. Notwithstanding these shortcomings, it is probable that they will form important management options for vegetation communities deemed to be of high enough conservation value to justify their recovery (e.g. Toolibin Lake in Western Australia, Chowilla floodplain in South Australia).

Living with salt: In areas of native vegetation the implications of choosing to live with increasing salinisation is that the plant ecology will evolve to a range of more salt tolerant species. This may have flow-on effects on other components of the ecology and may also have implications for human uses of the site. The key to successful management in these areas is to prevent, as much as possible, any further soil degradation.

In discharge areas where vegetation communities are suffering dieback or have been destroyed by salinisation, there are a number of additional options that can be considered:

Revegetation with salt tolerant trees and shrubs: This is often carried out with the aim of improving the aesthetics of the discharge area, stabilising any erosion and other degradation of the soils, and lowering the underlying water table. However, it is often misunderstood that transpiration of saline groundwater by vegetation will lead to build-up of salt in the soils, causing eventual death of the trees (e.g. Hatton et al., 1998), and so in the long term will reduce the aesthetic and erosion control benefits. Irrigation of the plantations will assist in leaching accumulated salt from the soil, however this is



unlikely to be an option in most areas, and even when it is it is likely to be expensive. Revegetation is unlikely to increase groundwater discharge rates significantly as transpiration of saline groundwater generally occurs at rates less than 1 mm day-1 (Thorburn, 1996; Morris et al., 1998; Morris and Collopy, 1999), comparable to discharge from bare soils. It therefore provides only minimal water table control (George et al., 1999), and in addition, has a high risk of tree mortality. Field and modelling results reported by George et al. (1999) and George et al. (2001) suggests that revegetation in recharge areas will only lead to significant reductions in water table levels if considerable areas of catchments (>50%) are planted. Furthermore, they will be more effective in local-scale aquifers with high transmissivity than regional-scale ones, and the impacts rarely extend more than 30 m from the planted area. Vertessy et al. (2002) provide a good summary of issues concerned with planting trees in saline areas.

Improving the inundation/flooding regime: Any additional water that can be provided to a discharge area is likely to be of benefit for leaching accumulated salt in the soils from the plant root zone and to provide a supplementary water supply. This is most easily achieved by manipulation of low salinity lateral sub-surface and surface water flows to direct them to the discharge area. However, care must be taken to ensure that unintended waterlogging of the area does not occur. It is also important to be aware that holding water at high levels for long periods in wetlands can result in the raised of groundwater levels in the surrounding area. The only time water should be held in wetlands for long periods of time is in situations where historically the wetland was a permanent water body. In all other cases, wetlands should be managed to provide alternating periods of wetting and drying, as close as possible to the historic behaviour.

CHAPTER 8 MONITORING


CHAPTER 8 MONITORING In the previous chapters we discussed methodologies for identifying a threatened vegetation community, assessing its current health, and determining the causes and processes leading to the threat. Having determined its conservation value, designed an agreed management plan to prevent further degradation or to actively restore the community, the final step is to (i) assess risks, and (ii) design an on-going plan to monitor the progress of the improved management.

Management of a vegetation community affected by salinity will be a long-term process and so the monitoring plan will need to account for this. It will also need to recognise that staff are likely to change throughout the course of the plan and therefore well designed and communicated protocols for sampling and data storage, recovery and review will need to be implemented.

A good example of the long-term commitment required is the monitoring from 1977 to present of Toolibin Lake in Western Australia.

Water Table and Salinity Changes in Time

Continual monitoring of groundwater depth and salinity, both within the threatened vegetation community and in the surrounding area, is important for assessing the on-going salinisation threat and the benefits of management that have been implemented.

Records of groundwater depth are most useful for assessing risk when sufficiently long and frequent data are available. When interpreting groundwater data it is important to be aware that water tables can fluctuate at a range of temporal scales. For example (Figure 32), they can be episodic in response to very large rainfall events, fluctuate due to varying climatic conditions, or can exhibit long-term water table rise or fall in response to land use changes. They can also demonstrate various combinations of these behaviours. In order to account for seasonal and episodic variation in groundwater levels and establish long-term trends, it is necessary to monitor water table depths on at least a monthly basis. It is also important to be aware that in many situations rising water tables are driven by increasing pressures in underlying semi-confined and confined aquifers, and so installation of piezometers at multiple depths at a site is often required. Also of importance is to interpret the data in the context of the groundwater flow systems they are monitoring. Tools such as FLOWTUBE (Dawes et al., 2000) can assist in reviewing and interpreting groundwater level data in this context. Groundwater salinities generally fluctuate much less than water table levels and so annual measurements are usually sufficient



Figure 32. Examples of hydrographs showing continuous water table rise due to land use changes,

episodic rise due to large rainfall events, and fluctuations in response to varying climatic conditions (data courtesy of Department for Water Resources, South Australia).

Rainfall is displayed as cumulative deviation to show the long-term trend.

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Photopoints Photopoints are established to provide visible evidence of vegetation and landscape changes over time. A protocol is established so that subsequent photographers can repeat precisely the photograph taken. Two markers are installed, one with height markings in the site to be photographed, the other “camera peg” approximately 10m to its north (to ensure the sun is usually behind the photographer). The lens of the camera is set at a determined height (generally ~1.5m) above the ground and it is focused on the site marker at exactly 1.5m above ground. Future photos adopt the same procedure. Examples of the use of photopoints for two sites on the River Murray floodplain are shown in Figure 33.

Figure 33. Photopoints at two sites on the River Murray floodplain. In both cases dieback of the

trees between the two times is clearly evident. Note the inconsistancy in camera positioning between (a) and (b).

(a) Site 1. 16/05/1996 (b) Site 1. 18/10/2000

(c) Site 2. 16/05/1996 (d) Site 2. 09/11/1999

(a) Site 1. 16/05/1996 (b) Site 1. 18/10/2000

(c) Site 2. 16/05/1996 (d) Site 2. 09/11/1999



Detailed Vegetation Growth Monitoring To obtain representative long-term growth measurements, multiple numbers of trees within a defined area (quadrat) should be monitored. Tree growth can be measured by a number of different parameters. Tree height can be determined from measuring the slope to the top of a tree using a clinometer and corrected for observer height and distance from the tree base. Crown diameter can be derived from the mean of two measurements of projected foliage taken at 90° to each other. Trunk diameter is normally measured at a standard height (typically 1.5 m), and is referred to as diameter at breast height (DBH). Leaf area is both difficult and time consuming to measure, but is the most sensitive of all of the methods, particularly for slow growing trees. Leaf area is most easily carried out using the “Adelaide” method (Andrew et al., 1979). For dense canopies, faster indirect methods that rely on correlations between total leaf area and light penetration can be used (Martens et al., 1993; Chen, 1996; Nackaerts et al., 2000).

part four Summary

CHAPTER 9. CONCLUDING REMARKS


CHAPTER 9. CONCLUDING REMARKS Over recent years literature has become available on the field responses of vegetation to salinity. From this we know that vegetation health in saline areas is not only controlled by the depth to the water table, but also by groundwater salinity, soil type, plant rooting depth and salinity tolerance, and the frequency and duration of leaching events. This improved understanding of the processes of soil salinisation and consequent vegetation health decline has progressed the simple concept of a 2 m critical water table depth being the main criteria for salinity risk. Whilst our understanding of the vegetation responses to salinity is generally good, it should be emphasized that it is based on only the few select species that have been studied intensively. There is a need for further studies on species that are widely distributed in areas at risk of salinisation.

There is now a range of tools available for critical analysis where salinity is threatening a vegetation community. At a bare minimum, some site characterisation is always required as part of desktop and modelling studies. The more field information collected, the greater the confidence in the understanding of the processes and the predictions of future outcomes from improved management. As with all forms of monitoring, the best results come from programs that commence early, measure often, and continue for long periods of time. While a range of tools exist for analysing individual sites, further development of methodologies that scale from individual sites up to the community and regional scale are required. Better remote sensing techniques for large-scale mapping of vegetation composition and health are integral to this capability.

The management of threatened vegetation communities is not only a biophysical issue, but also a socio-economic issue. The level of intervention required for full protection of vegetation is likely to be expensive in most circumstances. Hence, for individual cases there will always be tradeoffs that recognize the intrinsic conservation value, the capital and on-going costs of restoration, stakeholder expectations, etc. Setting of clear management goals that meet the environmental outcomes agreed to by all stakeholders is crucial for this process to succeed.

CHAPTER 10. KNOWLEDGE GAPS


CHAPTER 10. KNOWLEDGE GAPS A number of obvious knowledge gaps have been identified in the preparation of these guidelines. It is recognized however, that they are in no way comprehensive, and are merely the opinions of the authors.

1. Detailed investigations of unstudied vegetation communities. Further detailed research sites of key vegetation communities should be established to add value to the existing knowledge base. These study areas should be chosen to provide information on species that are widely distributed in areas threatened by salinity, but for which little information currently exists. They should also be targeted to include sites where health decline is thought to be due to a combination of the effects of salinity, waterlogging and/or drought, as these interactions are still poorly understood. As discussed above, much of our understanding of vegetation responses to salinity comes from studies of a handful of species, in a small number of locations.

2. Research into the influence that ageing plays in the health of long-lived tree species. At present, it is not known whether the decline in tree health is a response to ageing, as well as changed environmental conditions. Ageing may also play a role in the capacity of an individual plant to adjust to changed environmental conditions. The effects of ageing may take the form of accumulated stress, where a young tree that has not experienced as many droughts is able to survive, while an older tree in the same environment dies. Alternatively, stress can lead to loss of function in older trees and so the community decline in health may be related to predominance of non-reproducing geriatric trees, rather than stressful environmental conditions. The declining health of this community would need to be addressed in terms of encouraging recruitment, rather than managing the environmental conditions to enhance the health of the aging population. The influence of tree ageing has not been taken into account in these guidelines, as this issue has not, to our knowledge, been studied in Australia.

3. Further development of methodologies to scale site understanding to the community and regional scale is required. As discussed above, most of the current analysis tools are aimed at studying conditions and processes at individual site. Whilst some research has commenced in this area (Holland et al., 2002), it is still in its infancy.

4. Further development of remote sensing techniques for large-scale mapping of vegetation composition and changes in health over time. While some work in this area has commenced (Overton et al., 1994; Overton et al., 1996), the potential usefulness of this approach is such that greater efforts to develop robust techniques is warranted.

part five References

REFERENCES


AFFA. (1992). National Strategy for Ecologically Sustainable Development. Agriculture Fisheries and Forestry Australia, Canberra.

AFFA. (1999a). Managing Natural Resources in Rural Australia for a Sustainable Future. Agriculture Fisheries and Forestry Australia, Canberra.

AFFA. (1999b). Progress in Implementation of the COAG Water Reform Framework. Report to COAG by High Level Steering Group on Water. Occasional Paper. Agriculture Fisheries and Forestry Australia, Canberra.

AFFA. (2000). National Action Plan for Salinity and Water Quality [Web Page]. Available at: http://www.affa.gov.au/docs/nrm/actionplan/index.html.

Akeroyd, M.D., Tyerman, S.D., Walker, G.R. and Jolly, I.D. (1998). Impact of flooding on the water use of semi-arid riparian eucalypts. Journal of Hydrology 206, 104-17.

Akilan, K., Farrell, R.C.C., Bell, D.T. and Marshall, J.K. (1997a). Responses of clonal river red gum (Eucalyptus camaldulensis) to waterlogging by fresh and salt water. Australian Journal of Experimental Agriculture 37, 243-48.

Akilan, K., Marshall, J.K., Morgan, A.L., Farrell, R.C.C. and Bell, D.T. (1997b). Restoration of catchments water balance: responses of clonal river red gum (Eucalyptus camaldulensis) to waterlogging. Restoration Ecology 5, 101-8.

Allen, J.A., Chambers, J.L. and Stine, M. (1994). Prospects for increasing the salt tolerance of forest trees: a review. Tree Physiology 14, 843-53.

Allen, J.A., Pezeshki, S.R. and Chambers, J.L. (1996). Interaction of flooding and salinity stress on baldcypress (Taxodium distichum). Tree Physiology 16, 307-13.

Andrew, M.H., Noble, I.R. and Lange, R.T. (1979). A non-destructive method for estimating the weight of forage on shrubs. Australian Rangelands Journal 1, 225-31.

ANZECC Taskforce on Salinity and Biodiversity. (2001). Implications of Salinity for Biodiversity Conservation and Management. Australian and New Zealand Environmental Conservation Council, Canberra.

ARMCANZ and ANZECC. (1996). National Principles for the Provision of Water for Ecosystems. Occasional Paper SWR No. 3. Agriculture and Resource Management Council of Australia and New Zealand and the Australian and New Zealand Environmental Conservation Council, Canberra.

Barnes, C.J., Allison, G.B. and Hughes, M.W. (1989). Temperature gradient effects on stable isotope and chloride profiles in dry soils. Journal of Hydrology 112, 69-87.

Barnett, S. (2000). Extent and Impacts of Dryland Salinity in South Australia. National Land and Water Resources Audit Dryland Salinity Project Report. Canberra.

Barrett-Lennard, E.G. (1986). Effects of waterlogging on the growth and NaCl uptake by vascular plants under saline conditions. Reclamation and Revegetation Research 5, 245-61.

Bastick, C. and Walker, M. (2000). Extent and Impacts of Dryland Salinity in Tasmania. National Land and Water Resources Audit Dryland Salinity Project Report, Canberra.

Beadle, N.C.W. and Costin, A.B. (1952). Ecological classification and nomenclature. Proceedings of the Linnean Society of New South Wales 77, 61-82.

Bell, D.T. (1999). Australian trees for the rehabilitation of waterlogged and salinity-damaged landscapes. Australian Journal of Botany 47, 697-716.

Bennett, D.L. and George, R.J. (1995). Using the EM38 to measure the effect of soil salinity on Eucalyptus globulus in south-western Australia. Agricultural Water Management 27, 69-86.

Bennett, D.L., George, R.J. and Whitfield, B. (2000). The use of ground EM systems to accurately assess salt store and help define land management options for salinity management. Exploration Geophysics 31-1, 249-54.

Benyon, R.G., Marcar, N.E., Crawford, D.F. and Nicholson, A.T. (1999). Growth and water use of Eucalyptus camaldulensis and E. occidentalis on a saline discharge site near Wellington, NSW, Australia. Agricultural Water Management 39, 229-44.

REFERENCES


Bleby, T.M., Aucote, M., Kennett-Smith, A.K., Walker, G.R. and Schachtman, D.P. (1997). Seasonal water use characteristics of tall wheatgrass (Agroyron elongatum (Host) Beauv.) in a saline environment. Plant, Cell and Environment 20, 1361-71.

Blythe, J.D., Burbidge, A.A., and Brown, A.P. (1995). Achieving cooperation between government agencies and the community for nature conservation, with examples from the recovery of threatened species and ecological communities. In, Nature Conservation 4: The Role of Networks. (Eds D.A. Saunders, J.L. Craig, and E.M. Mattiske.) pp. 343-67. Surrey Beatty & Sons Pty Ltd.

CAMBA. (1988). Agreement between the Government of Australia and the Government of the People's Republic of China for the Protection of Migratory Birds and their Environment [Web Page]. Available at: http://www.austlii.edu.au/au/other/dfat/treaties/1988/22.html.

Carbon, B.A., Bartle, G.A. and Murray, A.M. (1981). Water stress, transpiration and leaf area index in eucalypt plantations in a bauxite mining area in south-west Australia. Australian Journal of Ecology 6, 459-66.

Chen, J.M. (1996). Optically-based methods for measuring seasonal variation of leaf area index in boreal conifer stands. Agricultural and Forest Meteorology 80, 135-63.

Clemens, J., Campbell, L.C. and Nurisjah, S. (1983). Germination, growth and mineral ion concentrations of Casuarina species under saline conditions. Australian Journal of Botany 31, 1-9.

Clifton, C. (2000). Extent and Impacts of Dryland Salinity in Victoria. National Land and Water Resources Audit Project Report. Canberra.

CMS. (1983). Convention on the Conservation of Migratory Species of Wild Animals [Web Page]. Available at: http://www.wcmc.org.uk/cms/.

Colquhoun, I.J.; Ridge, R.W., Bell, David T.; Loneragan, W.A., and Kuo, J. (1984). Comparative studies in selected species of Eucalyptus used in rehabilitation of the northern jarrah forest, Western Australia. 1. Patterns of xylem pressure potential and diffusive resistance of leaves. Australian Journal of Botany. 32:367-373.

Cook, P.G., Walker, G.R., Buselli, G., Potts, I. and Dodds, A.R. (1992). The application of electromagnetic techniques to groundwater recharge investigations. Journal of Hydrology 130, 201-29.

Cook, P.C. and Williams, B.G. (1998). Part 8: Electromagnetic induction techniques. In, Studies in Catchment Hydrology: The Basics of Recharge and Discharge. (Eds Lu Zhang and Glen Walker.). CSIRO, Canberra.

Coram, Jane, (1998) (Ed.) National Classification of Catchments for Land and River Salinity Control. Rural Industries Research and Development Corporation. A report for the RIRDC/LWRRDC/FWPRDC Joint Venture Agroforestry Program. Report No. 98/78.

Craig, G.F., Bell, D.T. and Atkins, C.A. (1990). Response to salt and waterlogging stress of ten taxa of Acacia selected from naturally saline areas of Western Australia. Australian Journal of Botany 38, 619-30.

Cramer, V.A. and Hobbs, R.J. (2002). Ecological consequences of altered hydrological regimes in fragmented ecosystems in southern Australia: impacts and possible management responses. Austral Ecology (in press).

Cramer, V.A., Thorburn, P.J. and Fraser, G.W. (1999). Transpiration and groundwater uptake from farm forest plots of Casuarina glauca and Eucalyptus camaldulensis in saline areas of southeast Queensland, Australia. Agricultural Water Management 39, 187-204.

Crombie, D.S., Tippett, J.T. and Hill, T.C. (1988). Dawn water potential and root depths of trees and understorey species in south-western Australia. Australian Journal of Botany 36, 621-31.

Crossing, L. and Simons, J. (2000). Monitoring Groundwater Levels. Farmnote. Agriculture Western Australia, Perth.

Davidson, N.J. and Reid, J.B. (1989). Response of eucalypt species to drought. Australian Journal of Ecology 14, 139-56.

REFERENCES


Dawes, W.R., Stauffacher, M. and Walker, G.R. (2000). Calibration and Modelling of Groundwater Processes in the Liverpool Plains. CSIRO Land and Water Technical Report 5/00, Canberra.

Dawes, W., Gilfedder M., Stauffacher M., and Walker G. (2001). Salinity case studies of Australian groundwater flow systems. In 'Proceedings of 8th Murray Darling Basin Groundwater Workshop 2001, Victor Harbour, South Australia, Adelaide.

Department of Conservation and Land Management. (2001). State Salinity Action Plan 1996: Review of the Department of Conservation and Land Management's Programs - January 1997 to June 2000. Report to the Executive Director of the Department of Conservation and Land Management, compiled by K.J. Wallace. Department of Conservation and Land Management, Perth.

Department of Environment and Heritage.2001. Parks Web - Biodiversity - Legislation [Web Page]. Available at: http://www.dehaa.sa.gov.au/biodiversity/legislation.html.

Department of Land and Water Conservation. (1998). Water Sharing the Way Forward. Department of Land and Water Conservation, Sydney.

Department of Land and Water Conservation. (1999). A Proposal for Updated and Consolidated Water Management Legislation for New South Wales. White paper. Department of Land and Water Conservation, Sydney.

Department of Land and Water Conservation. (2000). An Overview of the Water Management Bill 2000. Department of Land and Water Conservation, Sydney.

Department of Land and Water Conservation. (2001a). Offsets, Salinity and Native Vegetation - Discussion Paper. Department of Land and Water Conservation, Sydney.

Department of Land and Water Conservation. (2002). The NSW State Groundwater Dependent Ecosystems Policy. NSW Government.

Department of Natural Resources and Mines. (2001). A Guide to Vegetation Management Policy in Queensland. Queensland Government, Brisbane.

Department of Natural Resources and Mines. (2001). Land and Water Management Plans: State Guidelines. Queensland Government, Brisbane.

Department of Primary Industries, Water and Environment. (2001). Tasmanian Natural Resources Management Strategy: Issues and Options Paper. Government of Tasmania, Hobart.

Dunn, G.M., Taylor, D.W., Nester, M.R. and Beetson, T.B. (1994). Performance of twelve selected Australian tree species on a saline site in southeast Queensland. Forest Ecology and Management 70, 255-64.

Eldridge, S.R., Thorburn, P.J., McEwan, K.L., and Hatton, T.J. (1993). Health and Structure of Eucalyptus Communities on Chowilla and Monoman Islands of the River Murray Floodplain, South Australia. Divisional Report . CSIRO Division of Water Resources, Adelaide, SA.

Environment Australia. (1998). Map of Australian Ramsar sites [Web Page]. Available at: http://www.ea.gov.au/water/wetlands/ramsar/index.html.

Environment Australia. (1999). Environment Protection and Biodiversity Conservation Act [Web Page]. Available at: http://www.ea.gov.au/epbc/index.html.

Environmental Protection Agency. (1999). Strategy for the Conservation and Management of Queensland's Wetlands. Queensland Government, Brisbane.

Environmental Protection Agency. (2000). Valuing the Environment. Summary of the Queensland Government's Environmental Management Program 2000/01. Queensland Government, Brisbane.

Feikema, P., Heuperman, A.F., Morris, J., and Connell, L. (1997). Impact of Eucalyptus plantation on hydrology and solute concentrations in shallow watertable areas. Murray Darling Workshop 97, Toowoomba, QLD, Dept. of Natural Resources, QLD.

Feikema, P.M. (2000). Tree growth and water relations in eucalypt plantations over shallow saline groundwater. Ph D Thesis. Dept. of Civil Engineering Monash University.

REFERENCES


Flowers, T.J., Troke, P.F. and Yeo, A.R. (1977). The mechanism of salt tolerance in halophytes. Annual Review of Plant Physiology 28, 89-121.

Flowers, T.J. and Yeo, A.R. (1986). Ion relations of plants under drought and salinity. Australian Journal of Plant Physiology 13, 75-91.

Freeze, R.A. and Cherry, J.A. (1979). Groundwater. Prentice Hall, Englewood Cliffs, New Jersey.

Froend, R.H., Halse, S.A. and Storey, A.W. (1997). Planning for the recovery of Lake Toolibin, Western Australia. Wetlands Ecology and Management 5, 73-85.

Froend, R.H., Heddle, E.M., Bell, D.T. and McComb, A.J. (1987). Effects of salinity and waterlogging on the vegetation of Lake Toolibin, Western Australia. Australian Journal of Ecology 12, 281-98.

Frost, F.M., Hamilton, B., Lloyd, M., and Pannell, D.J. (2001). Salinity: A New Balance, The Report of the Salinity Taskforce Established to Review Salinity Management in Western Australia. Government of Western Australia, Perth.

Gardner, W.R. (1958). Some steady state solutions of the unsaturated moisture flow equation with application to evaporation from a water table. Soil Science 85, 228-32.

George, R.J., McFarlane, D.J., and Speed, R.J. (1995). The consequences of a changing hydrologic environment for native vegetation in southwestern Australia. In, Nature Conservation 4: The Role of Networks. (Eds D.A. Saunders, J.L. Craig, and M. Mattiske.) pp. 9-22. Surrey Beattey & Sons Pty Ltd.

George, R.J., Beasley, R., Gordon, I., Heislers, D., Speed, R., Brodie, R., McConnell, C., and Woodgate, P. (1998). Evaluation of Airborne Geophysics for Catchment Management. Agriculture, Fisheries and Forestry Australia and National Dryland Salinity Program, Canberra.

George, R.J., Nulsen, R.A., Ferdowsian, R. and Raper, G.P. (1999). Interactions between trees and groundwaters in recharge and discharge areas – A survey of Western Australian sites. Agricultural Water Management 39, 91-113.

George, R.J., Clarke, C.J. and Hatton, T. (2001). Computer-modelled groundwater response to recharge management for dryland salinity control in Western Australia. Advances in Environmental Monitoring and Modelling 2(1), 3-35.

Gilfedder, M., Smitt, C., Dawes, W., Petheram, C., Stauffacher, M., and Walker, G. (2001). Impact of Increased Recharge on Groundwater Discharge: Development of a Simplified Function Using Catchment Parameters. Technical Report 23/01. CSIRO Land and Water, Canberra.

Gordon, I. (2000). Extent and Impacts of Dryland Salinity in Queensland. National Land and Water Resources Audit Dryland Salinity Project Report. Canberra.

Government of South Australia. (2000a). Directions for Managing Salinity in South Australia. Primary Industries and Resources SA, Adelaide.

Government of South Australia. (2000b). South Australian River Murray Salinity Strategy. Draft Edition. Department for Water Resources, Adelaide.

Government of South Australia. (2000c). State Dryland Salinity Strategy. Primary Industries and Resources, Adelaide.

Government of Victoria. (2000). Restoring Our Catchments. Victoria's Salinity Management Framework. Department of Natural Resources and Environment, Melbourne.

Government of Western Australia. (1999). State Natural Resource Management Framework Policy. Cabinet Standing Committee on Salinity Management, Perth.

Greacen, E.L., Walker, G.R., and Cook, P.G. (1986). Evaluation of the filter paper method for measuring soil water suction. International Meeting at University of Utah on Measurement of Soil and Plant Water Status. pp. 137-45.

Greenway, H. and Munns, R. (1980). Mechanisms of salt tolerance in non-halophytes. Annual Review of Plant Physiology 31, 149-90.

REFERENCES


Greenwood, E.A.N., Biddiscombe, E.F., Rogers, A.L., Beresford, J.D. and Watson, G.D. (1994). The influence of groundwater level and salinity of a multi -species tree plantation in the 500 mm rainfall region of south-eastern Australia. Agricultural Water Management 25, 179-84.

Greenwood, E.A.N., Biddiscombe, E.F., Rogers, A.L., Beresford, J.D. and Watson, G.D. (1995). Growth of species in a tree plantation and its influence on salinity and groundwater in the 400mm rainfall region of south-western Australia. Agricultural Water Management 28, 231-43.

Grimes, R.F. (1987). Crown Assessment of Natural Spotted Gum (Eucalyptus Maculata) and Ironbark (Eucalyptus Fibrosa, Eucalyptus Depranophylla) Forest. Technical Paper No. 7. Queensland Department of Forestry.

Halse, S.A., Pearson, G.B., and Patrick, S. (1993). Vegetation of Depth-Gauged Wetlands in Nature Reserves of Southwest Western Australia. Technical Report. Department of Conservation and Land Management, Perth, Western Australia.

Hatton, T.J. and Evans, R. (1998). Dependence of Ecosystems on Groundwater and Its Significance to Australia. Occasional Paper. LWRRDC, Canberra.

Hatton, T.J., Catchpole, E.A. and Vertessy, R.A. (1990). Integration of sapflow velocity to estimate plant water use. Tree Physiology 6, 201-9.

Hatton, T.J., Reece, P., Taylor, P.L. and McEwan, K. (1998). Does leaf water efficiency vary among eucalypts in water limited environments. Tree Physiology 18, 529-36.

Henschke, C. (2001). Monitoring groundwater. Agdex 552. Primary Industries and Resources, South Australia, Adelaide.

Heard, L. and Channon, B. (1997). Guide to Native Vegetation Survey (Agricultural Region) Using the Biological Survey of South Australia Methodology. Department of Housing and Urban Development, Adelaide.

Heuperman, A.F. (1995). Salt and Water Dynamics Beneath a Tree Plantation Growing on a Shallow Watertable. Institute of Sustainable Irrigated Agriculture, Tatura Centre. Department of Agriculture, Energy and Minerals Victoria.

Heuperman, A.F. (1999). Hydraulic gradient reversal by trees in shallow water table areas and repercussions for the sustainability of tree-growing systems. Agricultural Water Management 39, 153-67.

Heuperman, A.F., Stewart, H.T.L. and Wildes, R.A. (1984). The effect of eucalypts on water tables in an irrigation area of northern Victoria. Water Talk 52, 4-8.

Hobbs, R.J. (1993). Effects of landscape fragmentation on ecosystem processes in the Western Australian whealtbelt. Biological Conservation 64, 193-201.

Hobbs, R.J. (1998). Impacts of land use on biodiversity in southwestern Australia. In: Landscape Disturbance and Biodiversity in Mediterranean-Type Ecosystems (Eds. P.W. Rundel, G. Montenegro and F.M. Jaksic), pp. 81-106. Springer-Verlag, Berlin.

Hobbs, R.J. and Norton, D.A. (1996). Towards a conceptual framework for restoration ecology. Restoration Ecology 4, 93-110.

Hobbs, R.J. and Harris, J.A. (2001). Restoration ecology: repairing the Earth’s ecosystems in the new millennium. Restoration Ecology 9, 239-46.

Hobbs, R.J., Saunders, D.A. and Main, A.R. (1993). Conservation management in fragmented systems. In: Reintegrating Fragmented Landscapes: Towards Sustainable Production and Nature Conservation (Eds. R.J. Hobbs and D.A. Saunders), pp. 299-309. Springer-Verlag, New York.

Holland, K., Jolly, I., McEwan, K., Whyatt, R., Gabrovsek, C., Telfer, A., Mensforth, L., and Walker, G. (2002). Methodologies for the Assessment of Riparian Eucalypt Health on the Floodplains of the Lower River Murray. Technical Report, CSIRO Land and Water, Adelaide (in press).

Hunt, N. and Gilkes, R. (1992). Farm Monitoring Handbook: A Practical Down-to-Earth Manual for Farmers and Other Land Users. University of Western Australia, Nedlands.

REFERENCES


JAMBA. (1981). Agreement between the Government of Australia and the Government of Japan for the Protection of Migratory Birds in Danger of Extinction and their Environment [Web Page]. Available at: http://www.austlii.edu.au/au/other/dfat/treaties/1981/6.html.

Jarwal, S.D., Jolly, I.D., and Kennett-Smith, A.K. (1996). The Salt Tolerant Grasses Puccinellia (Puccinellia spp.) and Tall Wheat Grass (Agropyron elongatum): A Literature Survey of Their Salt Tolerance, Establishment, Water Use, and Productivity. Technical Memorandum 96/7. CSIRO Division of Water Resources, Adelaide.

Jolly, I.D. (1996). The effects of river management on the hydrology and hydroecology of arid and semi-arid floodplains. In, Floodplain Processes. (Eds M.G. Anderson, D.E. Walling, and P.D. Bates.) pp. 577-609. John Wiley & Sons Ltd., Chichester, New York.

Jolly, I.D., Walker, G.R. and Thorburn, P.J. (1993). Salt accumulation in semi-arid floodplain soils with implications for forest health. Journal of Hydrology 150, 589-614.

Jolly, I.D. and Walker, G.R. (1996). Is the field water use of Eucalyptus largiflorens F. Muell. affected by short-term flooding? Australian Journal of Ecology 21, 173-83.

Jolly, I.D., Walker, G.R., and Thorburn, P.J. (1994). Salt balances in semi-arid floodplain soils and consequences for riparian vegetation health. In proceedings 'Water Down Under 1994- International Groundwater and Hydrology Conference, Adelaide, SA, Australian National Conference Publication No 94/14 pp. 687-90. The Institution of Engineers, Barton, ACT.

Kennett-Smith, A.K., Streeter, T.C., Taylor, P., and Thorburn, P.J. (1993). Tree water use patterns in an area with shallow, saline groundwater. In proceedings 'National Conference on Land Management for Dryland Salinity Control, Bendigo 28 September to 1 October 1993, La Trobe University.

Lambert, Marcia and Turner, John (2000). Commercial forest plantations on saline lands. CSIRO Publishing, Collingwood.

Landsberg, J. and Wylie, F.R. (1983). Water stress, leaf nutrients and defoliation: a model of dieback of rural eucalypts. Australian Journal of Ecology 8, 27-41.

Lay, B.G. and Meissner, A.P. (1985). An objective method for assessing the performance of amenity plantings. Journal of the Adelaide Botantical Gardens 7, 159-66.

Levitt, J. (1980). Water, radiation, salt and other stresses. II edition. Academic Press, New York.

Lewis, D. W. (1983). Practical sedimentology. Hutchinson Ross, Pennsylvania.

Littleboy, M., Piscopo, G., Beecham, R., Barnett, P., Newman, L., and Alwood, N. (2000). Dryland Salinty Extent and Impacts in New South Wales. National Land and Water Resources Audit Project Report, Canberra.

Marcar, N., Ismail, S., Hossain, A., and Ahmed, R. (1999). Trees, Shrubs and Grasses for Saltland: an Annotated Bibliography. ACIAR Monograph . Australian Centre for International Agricultural Research, Canberra.

Marcar, N.E. (1993). Waterlogging modifies growth, wateruse and ion concentrations in seedlines of salt treated Eucalyptus camaldulensis, E. tereticornis, E. robusta and E. globulus. Australian Journal of Plant Physiology 20, 1-13.

Marcar, N.E., Arnold, R. and Benyon, R.G. (2000). Trees for saline environments. Natural Resource Management Special Issue June 2000, 14-18.

Marcar, N.E., Crawford, D.F., Leppert, P., Jovanovic, T., Floyd, R., and Farrow, R. (1995). Trees for saltland: a guide to selecting native species for Australia. CSIRO, Australia.

Margules and Partners, P and J Smith Ecological Consultants, and Victorian Department of Conservation, Forests and Lands. (1990). Riparian Vegetation of the River Murray. Murray Darling Basin Commission, Canberra.

Martens, S.N., Ustin, S.L. and Rousseau, R.A. (1993). Estimation of tree canopy leaf area index by gap fraction analysis. Forest Ecology and Management 61, 91-108.

REFERENCES


Martin, L. and Metcalfe, J. (1998). Assessing the Causes, Impacts, Costs and Management of Dryland Salinity. National Dryland Salinity Program Occasional Paper No. 20/98. Land and Water Australia, Canberra.

McDonald, R.C., Isbell, R.F., Speight, J.G., Walker, J., and Hopkins, M.S. (1990). Australian soil and land survey. Field handbook. 2nd edition. Inkata Press, Melbourne.

McEvoy, P.K. (1992). Ecophysiological comparisons between Eucalyptus camaldulensis Dehnh., E. largiflorens F. Muell. and E. microcarpa (Maiden) Maiden on the River Murray Floodplain. Master of Forest Science Thesis. Faculty of Agriculture and Forestry, University of Melbourne.

McEwan, K.L., Holub, A.N., Walker, G.R., Jolly, I.D., Thorburn, P.J., and Kennett-Smith, A.K. (1991). Compilation of Soil Water and Chloride Profiles From the Chowilla Anabranch Region, South Australia. Technical Memorandum 91/17. CSIRO Division of Water Resources, Adelaide.

McNeill, J.D. (1986). Rapid, Accurate Mapping of Soil Salinity Using Electromagnetic Ground Conductivity Meters. Technical Note TN-18. Geonics Ltd., Ontario.

Mensforth, L.J., Thorburn, P.J., Tyerman, S.D. and Walker, G.R. (1994). Sources of water used by riparian Eucalyptus camaldulensis overlying highly saline groundwater. Oecologia 100, 21-28.

Mensforth, L.J. and Walker, G.R. (1996). Root dynamics of Melaleuca halmaturorum in response to fluctuating saline groundwater. Plant and Soil 184, 75-84.

Mensforth, L.J. (1996). Water use strategy of Melaleuca halmaturorum in a saline swamp. PhD thesis. The University of Adelaide.

Morris, J. and Collopy, J. (1999). Water use and salt accumulation by a plantation of Eucalyptus camaldulensis and Casuarina cunninghamiana with shallow saline groundwater. Agricultural Water Management 39, 205-27.

Morris, J., Mann, L. and Collopy, J. (1998). Transpiration and canopy conductance in a eucalypt plantation using shallow saline groundwater. Tree Physiology 18, 547-55.

Munns, R. (1993). Physiological processes limiting plant growth in saline soils: some dogmas and hypotheses. Plant, Cell and Environment 16, 15-24.

Murray-Darling Basin Commission.1998. Floodplain Wetlands Management Strategy [Web Page]. Available at: http://www.mdbc.gov.au/naturalresources/policies%5Fstrategies/projectscreens/flood_wetlands_management.htm.

Murray-Darling Basin Ministerial Council. (1999). The Salinity Audit of the Murray-Darling Basin. A 100-Year Perspective. Murray-Darling Basin Ministerial Council, Canberra.

Murray-Darling Basin Ministerial Council. (2000). Draft Basin Salinity Management Strategy 2001-2015. Draft Ed. Murray-Darling Basin Ministerial Council, Canberra.

Murray-Darling Basin Ministerial Council. (2001). Integrated Catchment Management in the Murray-Darling Basin 2001-2010: Delivering a Sustainable Future. Draft Ed. Murray-Darling Basin Ministerial Council, Canberra.

Myers, B.A. and Neales, T.F. (1984). Seasonal changes in the water relations of Eucalyptus behriana F.Muell. and E. microcarpa (Maiden) Maiden in the field. Australian Journal of Botany 32, 495-510.

Nackaerts, K., Coppin, P., Muys, B. and Hermy, M. (2000). Sampling methodology for LAI measurements with LAI-2000 in small forest stands. Agricultural and Forest Meteorology 101, 247-50.

National Environmental Consultancy. (1988). Chowilla Salinity Mitigation Scheme, Draft Environmental Impact Statement. Engineering and Water Supply Department, Adelaide.

Native Vegetation Advisory Council NSW. (1999). Setting the Scene: The Native Vegetation of New South Wales. Background Paper Number 1. Department of Land and Water Conservation, Sydney.

REFERENCES


Native Vegetation Advisory Council NSW. (2000a). Native Vegetation Conservation Strategy for New South Wales. Draft Ed. Department of Land and Water Conservation New South Wales.

Native Vegetation Advisory Council NSW. (2000b). Arrangements and Opportunities for Native Vegetation Management in New South Wales. Background Paper Number 6. Department of Land and Water Conservation, Sydney.

Natural Resources and Environment. (2000). Restoring Our Catchments: Victoria's Draft Native Vegetation Management Framework. Department of Natural Resources and Environment, Victoria.

New South Wales Government. (2000). NSW Salinity Strategy: Taking on the Challenge. NSW Department of Land and Water Conservation, Sydney.

Niknam, S.R. and McComb, J. (2000). Salt tolerance screening of selected Australian woody species - a review. Forest Ecology and Management 139, 1-19.

NLWRA (2001). Australian Dryland Salinity Assessment 2000. National Land and Water Resources Audit, Canberra.

Northern Arthur River Wetlands Committee. (1987). The Status and Future of Lake Toolibin As a Wildlife Reserve. Water Authority of Western Australia, Perth.

NSW State Wetland Action Group. (2000). Wetland Action Plan 2000/2003. Sydney.

Overton, I.C., Lewis, M., and Walker, G.R. (1994a). Vegetation mapping of the Chowilla Anabranch region using Landsat TM and digital orthophotography. River Murray Mapping Conference, Lake Hume.

Overton, I.C., Lewis, M., and Walker, G.R. (1996). Detecting vegetation change on a semi-arid floodplain using Landsat TM, Chowilla, South Australia. 8th Australasian Remote Sensing Conference, Canberra.

Overton, I., Newman, B., Erdmann, B., Sykora, N., and Slegers, S. (1999). Modelling floodplain inundation under natural and regulated flows in the lower River Murray. Second Australian Stream Management Conference: the Challenge of Rehabilitating Australia's Streams, Adelaide, (Eds I. Rutherfurd and R. Bartley) CRC for Catchment Hydrology, Melbourne.

Passioura, J.B., Ball, M.C. and Knight, J.H. (1992). Mangroves may salinise the soil and in doing so limit their transpiration rate. Functional Ecology 6, 476-81.

Peck, Adrian J. (1978). Note on the role of a shallow aquifer in dryland salinity. Australian Journal of Soil Research. 16:237-240.

Petheram, C., Zhang, L., Walker, G. and Grayson, R. (2000). Towards a Framework for Predicting Impacts of Land-use on Recharge: A Review of Recharge Studies in Australia. Technical Report 28/00, CSIRO Land and Water, Canberra.

Ponnamperuma, F.N. (1972). The chemistry of submerged soils. Advances in Agronomy 24, 19-96.

Pook, E.W., Costin, A.B. and Moore, C.W.E. (1966). Water stress in native vegetation during the drought of 1965. Australian Journal of Botany 14, 257-67.

PPK Environment and Infrastructure. (1998). Assessment of the Impact of the Bookpurnong/ Lock 4 Irrigation District on Floodplain Health and Implications for Future Options.

PPK Environment and Infrastructure and CSIRO Land and Water. (1997). Managing Dryland Salinity in the Upper South East: Implications of Some Recent Groundwater Studies. Adelaide.

Ramsar. (1971). The Ramsar Convention on Wetlands [Web Page]. Available at: http://ramsar.org/.

Rayment, G.E. and Higginson, F.R. (1992). Australian Laboratory Handbook of Soil and Water Chemical Methods. Inkata Press, Sydney.

Revesz, K. and Woods, P.H. (1990). A method to extract soil water for stable isotope analysis. Journal of Hydrology 115, 397-406.

Salama, R.B. (Ed.)(1996). Physical and Chemical Techniques for Discharge Studies: Part 1 of the Basics of Recharge and Discharge. CSIRO Division of Water Resources, Canberra.

REFERENCES


Scholander, P.F., Hammel, H.T., Bradstreet, E.D. and Hemmingsen, E.A. (1965). Sap pressure in vascular plants. Science 148, 339-46.

Sharley, T. and Huggan, C. (1995). Chowilla Resource Management Plan: Final Report. Murray Darling Basin Commission, Canberra.

Short, R. and McConnell, C. (2000). Extent and Impacts of Dryland Salinity in Western Australia. National Land and Water Resources Audit Project Report, Canberra.

Silberstein, R., Vertessy, R.A., Morris, J. and Feikema, P. (1999). Modelling the effects of soil moisture and solute conditions on tree growth and water use: a case study from the Shepparton irrigation area. Agricultural Water Management 39(2-3), 283-315.

Sinclair Knight Merz. (1999). Chowilla Groundwater Control Scheme, Supplementary Investigations. Murray Darling Association.

Sinclair Knight Merz. (2001). Environmental Water Requirements of Groundwater Dependant Ecosystems. Draft Edition. Environment Australia.

Slavich, P.G., Smith, K.S., Tyerman, S.D. and Walker, G.R. (1999a). Water use of grazed salt bush plantations with saline watertable. Agricultural Water Management 39, 169-85.

Slavich, P.G., Walker, G.R., Jolly, I.D., Hatton, T.J. and Dawes, W.R.J. (1999b). Dynamics of Eucalyptus largiflorens growth and water use in response to modified watertable and flooding regimes on a saline floodplain. Agricultural Water Management 39, 245-64.

Specht, R.L. (1970). Vegetation. In, The Australian Environment. (Ed. G.N. Leeper) Melbourne University Press, Melbourne.

State Salinity Council. (2000a). Natural Resource Management in Western Australia. The Salinity Strategy. Government of Western Australia, Perth.

State Salinity Council. (2000b). Natural Resource Management in Western Australia. Salinity Actions. Government of Western Australia, Perth.

Stirzaker, R., Lefroy, T., Keating, B., and Williams, J. (2000). A Revolution in Land Use: Emerging Land Use Systems for Managing Dryland Systems. Report. CSIRO Land and Water, Canberra.

Stirzaker, R. and Vertessy, R. (2000). Trees, Water and Salt: An Australian Guide to Using Trees for Healthy Catchments and Productive Farms. Joint Venture Agroforestry Program Research Series No.1. Rural Industries and Development Corporation, Canberra.

Sun, D. and Dickinson, G.R. (1993). Responses to salt stress of 16 Eucalyptus species, Grevillea robusta, Lophostemon confertus and Pinus caribea var. hondurensis. Forest Ecology and Management 60, 1-14.

Sun, D. and Dickinson, G.R. (1995a). Survival and growth responses of a number of Australian tree species planted on a saline site in tropical north Australia. Journal of Applied Ecology 32, 817-26.

Swanson, R.H. and Whitfield, D.W.A. (1981). A numerical analysis of heat pulse velocity and theory. Journal of Experimental Botany 32, 221-29.

Talsma, T. (1963). The control of saline groundwater. Meded Landbouwhogeschool Oproekingsrtn, Staat Gent 63, 1-68.

Taras, M.J., Greenberg, A.E., Hoak, R.D., and Rand, M.C. (Editors)(1975). Standard Methods for the Examination of Water and Wastewater. 4th Ed. American Public Health Association.

Thorburn, P.J. (1996). Can shallow water tables be controlled by the revegetation of saline lands? Australian Journal of Soil and Water Conservation 9, 45-50.

Thorburn, P.J., Walker, G.R. and Woods, P.H. (1992). Comparison of diffuse discharge from shallow water tables in soils and salt flats. Journal of Hydrology 136, 253-74.

Thorburn, P.J., Hatton, T.J. and Walker, G.R. (1993a). Combining measurements of transpiration and stable isotopes of water to determine groundwater discharge from forests. Journal of Hydrology 150, 563-87.

REFERENCES


Thorburn, P.J., Walker, G.R. and Brunel, J.P. (1993b). Extraction of water from Eucalyptus trees for analysis of deuterium and oxygen-18: laboratory and field techniques. Plant, Cell and Environment 16, 269-77.

Thorburn, P.J., Walker, G.R. and Jolly, I.D. (1995). Uptake of saline groundwater by plants: an analytical model for semi-arid and arid areas. Plant and Soil 175, 1-11.

Tickell, S.J. (1994). The Risk of Dryland Salinity in the Northern Territory. Northern Territory Department of Land Planning and Environment.

Tickell, S.J. (1994a). Regional Salt Storage Northern Territory. Power and Water Authority of the Northern Territory. Water Resources Division.

Tickell, S.J. (1994b). Dryland Salinity Hazard Map of the Northern Territory. Water Resources Division. Power and Water Authority of the Northern Territory.

Tickell, S.J. (1997). Mapping dryland salinity hazard, Northern Territory, Australia. Hydrogeology Journal 5, 109-17.

Toolibin Lake Recovery Team and Toolibin Lake Technical Advisory Group. (1994). Toolibin Lake Recovery Plan. Unpublished plan. Department of Conservation and Land Management, Perth.

Topp, G.C., Reynolds, W.D., and Green, R.E. (1990). Proceedings of symposium 'Advances in Measurement of Soil Physical Properties: Bringing Theory into Practice, San Antonio, Texas, Soil Science of America, Special Publication Number 30 Wisconsin, USA.

Turner, N.C. (1981). Techniques and experimental approaches for the measurement of plant water status. Plant and Soil 58:339-366.

van der Moezel, P.G. and Bell, D.T. (1987). Comparative seedling salt tolerance of several Eucalyptus and Melaleuca species from Western Australia. Australian Forestry Research 17, 151-58.

van der Moezel, P.G. and Bell, D.T. (1990). Saltland reclamation: selection of superior Australian tree genotypes for discharge sites. Proceedings of the Ecological Society of Australia 16, 545-49.

van der Moezel, P.G., Pearce-Pinto, G.V.N. and Bell, D T. (1991). Screening for salt and waterlogging tolerance in Eucalyptus and Melaleuca species. Forest Ecology and Management 40, 27-37.

van der Moezel, P.G., Walton, C.S., Pearce-Pinto, G.V.N. and Bell, D.T. (1989). Screening for salinity and waterlogging tolerance in five Casaurina species. Landscape and Urban Planning 17, 331-37.

van der Moezel, P.G., Watson, L.E., Pearce-Pinto, G.V.N. and Bell, D.T. (1988). The response of six Eucalyptus species and Casuarina obesa to the combined effect of salinity and waterlogging. Australian Journal of Plant Physiology 15, 465-74.

Vertessy, R.A., Stirzaker, R. ., and Sarre, A. (2002). Trees, water and salt: and Australian guide to growing trees for productive farms and healthy catchments. RIRDC, Canberra.

Walker, G., Brunel, J.P., Dighton, J., Holland, K., Leaney, F., McEwan, K., Mensforth, L., Thorburn, P., and Walker, C. (2001a). The Use of Stable Isotopes of Water for Determining Sources of Water for Plant Transpiration. Technical Report . CSIRO Land and Water.

Walker, G.R. (2000). Robust systems for saline land: challenges in agriculture and conservation. Natural Resource Management Special Issue June 2000, 19-22.

Walker, G.R., Brunel, J.P., Dighton, J.C., Holland, K.L., Leaney, F.W., McEwan, K.L., Mensforth, L.J., Thorburn, P.J., and Walker, C.D. (2001b). Use of stable isotopes of water for determining sources of water for plant transpiration. In, The Practical Application of Stable Isotope Techniques to Study Plant Physiology, Plant Water Uptake and Nutrient Cycling. (Eds M.J. Unkovich, J. Gibbs, J.S. Pate, and A.M. McNeill.) Kluwer Academic Publishers, Dordrecht, The Netherlands.

Walker, G.R., Gilfedder, M., and Williams, J. (1999). Effectiveness of Current Farming Systems in the Control of Dryland Salinity. CSIRO Land and Water, Canberra.

Walker, G.R., Jolly, I.D., and Jarwal, S.D. (Editors)(1994). Salt and Water Movement in the Chowilla Floodplain. Water Resources Series. CSIRO Division of Water Resources, Adelaide.

REFERENCES


Warrick, A.W. (1988). Additional solutions for steady-state evaporation from a shallow water table. Soil Science 146(2):63-66.

Water and Rivers Commission. (2000a). Environmental Water Provisions Policy for Western Australia. Statewide Policy No. 5. Water and Rivers Commission.

Water and Rivers Commission. (2000b). Draft-Waterways WA Policy. Statewide Policy No. 4. Water and Rivers Commission, Perth.

Wouters, C. (1993). River Red Gum Dieback in the Lower Wimmera River Catchment. Department of Conservation and Natural Resources, Horsham.

Zhang, L. and Dawes, W.R. (1998). WAVES: An Integrated Energy and Water Balance Model. Technical Report 31/98. CSIRO Land and Water, Canberra.

Zhang, L., Dawes, W.R., Slavich, P.G., Meyer, W.S., Thorburn, P.J., Smith, D.J. and Walker, G.R. (1999). Growth and groundwater uptake response of lucerne to changes in groundwater levels and salinity: lysimeter, isotope and modelling studies. Agricultural Water Management 39, 265-82.

Zubrinich, T.M. (1996). An investigation of the ecophysiological, morphological and genetic characteristics of Eucalyptus largiflorens F. Muell. and Eucalyptus gracilis F. Muell; in relation to soil salinity and groundwater conditions throughout the Chowilla anabranch. PhD Thesis. Flinders University of South Australia, School of Biological Sciences, Adelaide.

part six Appendices

APPENDIX 1: DETERMINING MOISTURE, CHLORIDE AND OSMOTIC SUCTION CHARACTERISTICS OF SOIL SAMPLES

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APPENDIX 1: DETERMINING MOISTURE, CHLORIDE AND OSMOTIC SUCTION CHARACTERISTICS OF SOIL SAMPLES

Soil Moisture Content The gravimetric water content (grams of water per gram of dry soil, g/g) of a sampled soil interval expressed as Theta g. This is determined by weighing a 20-50g sub-sample of soil, oven drying the sample for 24 hours at 1050C then reweighing. Theta g (g/g) = ((container + wet soil) - (container +dry soil))

(container + dry soil) - container

Chloride The chloride ion concentration in the soil solution (milligrams of chloride per litre of soil water, mg/L). Total chloride in the soil sample (grams of chloride per kilogram of dry soil) is determined by laboratory methods such as colorimetry (Taras et al., 1975) and converted to the concentration in the soil solution by dividing by the gravimetric water content (Theta g).

Osmotic Suction or Potential The osmotic suction (megapascals, MPa) is estimated from the concentration of chloride per unit volume of moisture in the soil (assuming the chloride was present as NaCl) by taking into account the osmotic potential of a 1M NaCl solution, 4.5 MPa, and the molar mass of chloride, 35.5g. From this a conversion factor of 0.127 is calculated to derive the following formula for osmotic suction.

Osmotic Suction (MPa) = 0.127 x Chloride (mg/L) / 1000

Note: osmotic potential is the negative of the osmotic suction.

APPENDIX 2: FILTER PAPER METHOD OF MEASURING MATRIC SUCTION OR POTENTIAL ON LOOSE SOIL SAMPLES

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APPENDIX 2: FILTER PAPER METHOD OF MEASURING MATRIC SUCTION OR POTENTIAL ON LOOSE SOIL SAMPLES The matric suction of the soil is determined by the filter paper method (Greacen et al., 1986). Three Whatman® No.42 55mm diameter ashless filter papers are positioned evenly spaced into a 300-500ml jar of soil as per the following procedure:

1. Fill jar with approximately 1/4 of the soil. Tamp down the soil to produce a flat surface. Place a filter paper onto the surface ensuring that it is not touching the sides of the jar to minimise contact with any condensation. A rubber bung with a handle attached provides a suitable implement for tamping down the soil. The flat surface ensures a good contact between the soil and the paper. Sample numbers should be recorded on each paper, preferably in lead pencil. Adopt a standard procedure of numbering the papers from bottom to top (say 3, 2 1) to enable easier processing and identification of paper position for error determination, i.e. if paper number 1 is found to be consistently drier there may be a problem with moisture loss from the top of the jar.

2. Add another 1/4 of the soil, tamp down and position a filter paper; repeat, finishing with a layer of soil.

3. Replace lid and tape up the lid of the jar with electrical tape.

4. Place jars in a constant temperature room for a minimum of 6 days to allow the filter papers to come to equilibrium with the soil water.

5. Remove the papers one at a time from the jar with blunt forceps (to prevent moisture exchange from fingers). Do not remove all the papers at once from the soil in the jar, as they will quickly start to dry. Lightly brush the paper with a small (25mm) brush to remove any loose soil particles. Weigh the paper and record the weight to within 1 milligram. This procedure should be carried out as quickly as possible to avoid dehydration of the paper.

6. Position papers on a tray, preferably in a single layer, so as not to dislodge and lose any soil particles missed by the brush. Place in an oven at 1050 C for at least one hour.

7. Reweigh and record dry weight. When weighing the dry papers it is important not to remove the entire tray from the oven, as the filter papers will immediately begin to absorb moisture. It is preferable to position the balance near the oven and remove the papers singly for weighing. Otherwise several papers may be removed from the oven to a closed plastic bag and removed one at time from the bag for weighing. Always use blunts forceps when handling the papers.

8. Determine the gravimetric water content (W) of the filter papers: W (g/g) = wet paper-dry paper

dry paper

APPENDIX 2: FILTER PAPER METHOD OF MEASURING MATRIC SUCTION OR POTENTIAL ON LOOSE SOIL SAMPLES

84

9. Matric suction is determined from the moisture characteristic of the filter paper and the gravimetric water content (W):

For W < 0.453 S = exp (12.265-17.931W)

W > 0.453 S = exp (5.553-3.095W)

Where S is the matric suction in kilopascals (kPa) (to convert to megapascals (MPa) divide this number by 1000). This calculation should be done for the three filter papers and the average value calculated and used.

Total suction can be calculated by the addition of the osmotic and matric suctions. Matric and total potentials are the negative of their respective suctions.

Note: the method is limited to matric potentials between 1 and 1450 kPa, and provides the only satisfactory direct method of measuring suction in the range 50 to 300 kPa.

APPENDIX 3: ATTRIBUTES FOR INDEX OF VEGETATION HEALTH: LAY AND MEISNER (1985) METHOD

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APPENDIX 3: ATTRIBUTES FOR INDEX OF VEGETATION HEALTH: LAY AND MEISNER (1985) METHOD

HEALTH SCALE (0-5)

0 Plant dead 1. (a) No foliage, stems still green

(b) 100% dieback or suppression of terminal foliage, any new growth of resprouts unhealthy, chlorotic or absent

2. (a) 100% dieback or suppression of terminal foliage, new growth or resprouts healthy.

(b) Apparently chronic or systemic infection of dessication with 75-100% of foliage dead, lost or damaged

(c) Two or more factors under “3” below 3. (a) Whole plant showing chlorosis, including new growth (b) Most leaves lost on lower growth, healthy tip growth remaining. (c) 50-70% of foliage affected by disease and/or dessication.

(d) Death or dieback of a major stem or portion of canopy: remainder healthy

4. (a) Healthy plant but with significant (25-50%) leaves lost or damaged

(b) Healthy, but with minor stem or canopy damage (affecting less than 25% of plant).

(c) Chlorosis of non-terminal foliage (d) Slight ill-thrift generally apparent

5. Healthy, but includes plants with up to 25% of leaves damaged in some way.

VIGOUR SCALE (0-5)

0 Plant dead 1. (a) No recent increase in canopy: size less than 25%of optimum.

(b) New growth, but plant less than 10% of optimum.

2. (a) Growth less than 25% of optimum, new leaves but only slight recent increase in canopy size.

(b) Growth less than 25% of optimum, major stem resprouting. 3. Growth 25-50% of optimum.4. Growth 50-75% of optimum.5. Growth 75-100% of optimum.

APPENDIX 4: ATTRIBUTES FOR INDEX OF VEGETATION HEALTH: ELDRIDGE (1993) MODIFICATION OF GRIMES (1987) METHOD

86


Crown Size 5 points The crown is wide, deep and roughly circular in plan, without any obvious

faults.

4 points The crown has easily observed, but slight faults, such as lop sidedness or is partly undeveloped.

3 points Obvious deficiencies in size and /or shape are present.

2 points Small, poorly shaped crowns.

1 point Crown absent.

Crown Density 5 points Very dense leaf clumps with even distribution of clumps over the crown. Very

little light penetration the leaf clumps.

4 points Dense leaf clumps distributed unevenly over the crown.

3 points Clumps of average density with reasonable distribution or dense clumps very unevenly spread.

2 points Clumps are sparse and poorly spread.

1 point No leaves present on the crown.

Dead Branches 5 points No visible dead branchlets or branches in the crown apart from the thin twigs

immediately inside the new leaf development, and the lowest branches in the process of being shed.

4 points On close inspection dead branchlets are evident but not over all the crown.

3 points Large and/or small branches are dead but not over all the crown. These are easily observed.

2 points Large and small branches dead over most of the crown, which is obviously dying.

1 point All branches are dead

Crown Epicormic Growth 5 points No epicormic growth present.

4 points Epicormic growth can be seen in part of the crown.

3 points Epicormic growth is present over most of the crown.

2 points Epicormic growth is present over all of the crown and stem.

1 point No growth present on crown.


87

Diagrams Depicting Vegetation Health Index Attributes


88

Diagrams Depicting Vegetation Health Index Attributes (continued)

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