SUMMARIES OF STUDENT FIELD PROJECTS IN THE KAUAERANGA V A L L E Y (1982 and 1983)

by J . Ogden, N.D. Mitchell, J . H . Choat and Stage II ecology class

Department of Botany, Auckland University.

INTRODUCTION

The following account is a summary of "Individual Projects" carried out by students on the Population and Community Ecology (now 39.210) courses in 1982 and 1983. For various reasons similar synopses were not prepared in subsequent years although individual projects have con­tinued to be a feature of the course. Projects we grouped under general subject topics and by years, and each is identified by the names of the students carrying out the work.

The summary statement represents our conclusions from the work, based on an assessment of the student's report. In general this statement is briefer, and often more factual than the student's own conclusion i.e. we have attempted to express the most concrete results and/or the most conservative conclusion in as few words as possible. In almost all cases the field work was completed in one day only. Naturally the quality of the work reported varies considerably. Individual results should be used merely as a guide in planning future studies; they are not definitive statements to be quoted uncritically. However, with this proviso, the results do present some useful data on a variety of topics.

The Kauaeranga Valley runs from the north-east to the south-west in the Coromandel Ranges to the east of Thames (N.Z.M.S. 260, 1:50,000: Sheet T.12). The valley is the headquarters of the Coromandel Forest Park and a popular camping and tramping area. The work reported here was mainly carried out within one hour's walk of the Coromandel Forest Education Camps (grid ref. 466 554) which is the base for the field course.

The climate of the valley is mild, if wet. The average temperature of the warmest month (Feb) is c. 20°C, and that of the coolest (July) c. 10°C. Average rainfall is between 2000 and 3000 mm depending on elevation. Rainfall is generally higher in winter, but very localised falls can occur at any time of year, causing flooding.

The natural vegetation of the valley falls into the kauri-softwoods-hardwoods forest class of Nicholls (1971). The forests have been highly modified by the activities of man and introduced animals (especially goats and opossums). Only at the highest altitudes and on the boggy summit of Table Mountain (800m) do the present communities resemble their primaeval condition.

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Here the community is characterised by dominance of yellow silver pine (Lepidothamnus intermedius), tawari (Ixerba brexioides) and tawheowheo (Quintinia serrata). The valley sides and spurs were logged for kauri early this century and as a result almost all the vegetation is secondary. The least disturbed areas still carry tall tawa (Beilschmiedia tawa) — northern rata (Metrosideros robusta) forest, and logged areas are dominated by kamahi and/or towhai (Weinmannia spp.) re ware wa (Knightia excelsa) and kanuka (Kunzea ericoides). Average tree densities (10cm dbh) range from 1100 to 1700 ha 1 and basal areas are commonly c.75m2 ha 1 on the hillslopes.

The river flats were extensively modified by flooding in the kauri logging days, and their vegetation now comprises a suite of several stages, from young manuka (Leptospermum scoparium) to older kanuka (Kunzea ericoides) currently being overtopped by rewarewa and podocarps (mainly Podocarpus totara, P. Cunninghamii and Phyllocladus trichomanoides, but with other species represented in places). Incement cores from the larger Podocarps (and kauri) on the flats close to the Education camp indicate that most of them began life c. 1860 (i.e. they pre-date extensive logging activity).

Seedling populations on logs vs. forest floor

Campbell & Butler: Studied n = 6 logs and adjacent areas (2 x l m 2

samples/log and adjacent areas) Results:

Difference not statistically significant (p>0.05) due to small sample size and large variances. Total number of species on logs = 5.9; off logs = 4.3. Also average height of seedlings, 17.6cm on logs, 15.1cm off logs, but not significant due to high variance. Different height frequency distributions. Some species preferences were suggested — e.g. Coprosma robusta, ground; Dodonaea viscosa, logs.

Eskildsen & Menzies: Studied n = 10 logs with a paired t-test approach concentrating on individual species distribution rather than overall species population. However their raw data allow some figures compara­ble to Campbell and Butler's to be calculated. Total number of seedlings on logs = 53.5/m2

Total number of seedlings off logs = 12.1/m2

Total number of species on logs 8.7 ± 2.6 Total number of species off logs 6.7 ±2.1

INDIVIDUAL PROJECT SUMMARIES (1982)

Total number of seedlings on logs Total number of seedlings off logs

= 20/m2

= 9/m2

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Generally found larger numbers of seedlings than Campbell and Butler, but trends identical. Leptospermum seedlings were found to be significantly more abundant on logs than on the ground (light deman­ding) and all other species showed no significant difference. Leptospermum seedlings were the main reason for high seedling numbers on logs.

Harris & Barker: Examined 50 logs and adjacent areas for presence or absence of Knightia excelsa. Found no significant difference between numbers on and off logs.

Effects of light on seedling distribution

Coombe & Haywood: Used a light meter to classify quadrats according to their light environment, and examined the distribution of Knightia excelsa in relation to this factor. There was an indication (? significance) that K. excelsa was more common as a seedling in shaded areas, but achieved sapling status preferentially in canopy gaps.

Dodds & Hook: Simply classified quadrats according to their canopy status and showed that overall seedling diversity was greatest in clearings and declined beneath trees and further beneath ferns. (This trend was not significant according to Hook). Some species preferred clearings (Laurelia, Carpodetus) others preferred to grow beneath the canopy (tawa, nikau, Hedycarya, Knightia). Only orchids preferred the dense shade beneath ferns. (Hook showed that saplings (as opposed to seedlings) were preferentially located in clearings). NB: These results appear to confirm those of Coombe and Haywood with regard to Knightia seedling distribution — but note possible confusion with Elaeocarpus dentatus (hinau) seedlings, a difficulty not mentioned by either group!

Shaw, Diepraam & Turepu: Studied the size frequency distribution of Leptospermum (species unspecified!) in a succession and noted a negative relationship between seedling abundance of Leptospermum and tree basal area. This suggests that Leptospermum seedlings are light requiring, a result also suggested by their marked preference for logs (noted by Eskildsen and Menzies). Note: Laboratory studies with L. scoparium seeds give the following results (mean % germination ± standard error)

These results suggest that temperature fluctuation may be more

Temp °C: 21° (constant) 21° (constant)

17/25° (fluctuating)

light 10.2 ± 3.4 darkll.7± 1.6 light 22.2 ± 7.7

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important than light.

Effects of seed dispersal mechanism on seedling distribution pattern

Williams & Cornford: Compared seedling distribution patterns around 4 parent trees of Knightia excelsa and 3 of Prumnopitys ferruginea (miro). Knightia is wind dispersed and was not randomly distributed about its parent trees, having more on the south and west sides, although this could have been due to one tree only unduly influencing the results (Williams). Miro is bird dispersed and was randomly distributed with regard to direction. The numbers of miro seedlings declined with distance from the parent tree while the number of Knightia seedlings tended to increase. (Miles and Cook showed no association between Knightia litter and Knightia seedlings and sug­gested that seeds were "randomly distributed".

Tree ferns as germination sites for forest trees

Mortimer & Perkin: Effect of tree fern morphology on seedling establishment.

Height and canopy diameter frequency distribution would be useful. Seedling abundance either on or beneath the ferns could not be clearly related to these differences. Seedling abundance on trunks; greatest Dicksonia squarrosa; least Cyathea dealbata Seedling abundance beneath trunks: greatest Cyathea medullaris; least C. dealbata (Note: low seedling abundance associated with Cyathea dealbata in this study c.f. Flavell, Lindsay and Hassall).

Crossley & Gilbert: Studied 20 individuals each of D. squarrosa and Cyathea dealbata. Found generally more seedlings beneath Dicksonia squarrosa than beneath C. dealbata (10 vs 5).

Sewell & Kerrigan: Also examined tree fern morphology and calcu­lated ratio of trunk area: area shaded by fronds. Dicksonia squarrosa = 1:2 Cyathea smithii = 1:3 Cyathea dealbata = 1:5 Adjusted seedling densities accordingly and concluded that there was no significant difference between seedling population on tree fern trunks and on the ground beneath them, except in the case of D. squarrosa,

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where significantly (P < .05) more seedlings were found on trunks than on adjacent ground (2.4 vs 0.8). The number of seedlings on D. squarrosa trunks was not statistically significant compared to that on the other ferns. This is to be interpreted as a reduction of seedling numbers on the ground beneath D. squarrosa. (This is in agreement with results of Flavell, Lindsay and Hassall). Showed that Weinmannia was more common on trunks than on an equivalent area of ground, while Pseudopanax arboreus was more common on the ground. C. smithii had significantly less moss cover than the other species.

Flavell, Lindsay & Hassall: By mapping illustrated the role of D. squarrosa in reducing seedling populations beneath its canopy area. Found more seedlings beneath C. dealbata than beneath D. squarrosa (27 ± 11 vs 9 ± 5/canopy radius), also for saplings (1.7 vs0.4). Species rankings (i.e. composition) did not differ. Concluded that seedlings were generally more abundant at margins of area shaded by tree ferns and in areas away from tree ferns. (These results agree with those of Sewell and Kerrigan, but note that Mortimer and Perkin found more seedlings beneath D. squarrosa than beneath C. dealbata, as also did Crossley and Gilbert).

Grant-Mackie & Weeber: Studied tree ferns as "potential roosting areas" for Weinmannia and Pseudopanax seedlings. Showed that seedlings were generally restricted to lower 4m of tree fern trunks. Pseudopanax showed no preference for any particular species, but was generally higher on the trunk than Weinmannia. Weinmannia preferred Cyathea medullaris. Wright & Glynn: Studied site preferences of seedling Weinmannia and Pseudopanax arboreus. Inappropriate tests showed no significance between seedling abundance of either species on the forest floor vs tree fern trunks, but Weinmannia was clearly much more abundant on tree fern trunks.

Druit & Crowe: Also found Weinmannia abundant in tree ferns, although pukatea was more abundant in some areas. Noted tendency for all seedlings to be on the same side of the trunk in any area, but the side differed in the two areas studied. Suggested that air currents carrying seeds might be responsible.

Effects of litter on seedling distribution

Walmsley & Miller: Examined Weinmannia seedling distribution in relation to litter depth (or "humus layer") and on tree fern trunks. Concluded that seedlings were absent where thick litter had accumu-

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lated although they were still present on nearby tree ferns (indicating presumably that a seed-rain was present, but seeds failed to germinate or establish where there was a thick litter).

Cook & Miles: Studied leaf litter type and associated seedling specie using X 2 contingency tables. Found a number of positive and negative associations between litter types and species of seedlings but failed t reach any overall conclusions, except that litter type does have a role ti play in determining the pattern of seedling distribution on the fores floor.

Tree fern distribution

Bayley, Turbott, Atkinson & Cotton: Examined altitudinal sequence of the different tree fern species. Concluded that Cyathea Smithii preferred higher altitudes than other species and that Dicksonia squarrosa had the widest altitudinal range.

Graig & Carter: Role of tree ferns in succession. Showed that seedlings of tree ferns were predominantly in younger forest, with larger specimens in older forest. (Studied plots with tree basal area range from 17 to 96m 2/ha). Cyathea medullaris found only in mature forest. NB. It was the lowest altitudinal species of the previous group — not being recorded by them above 650m).

Invasion of pine forest by native tree seedlings

Worthington: Compared tree seedling populations in pines and area 1. He recorded population sizes as follows in the pines (But reached no conclusion). seedlings 10.7/m2

Saplings 3.2/m2

Striplings 1.4/m2

Trees 0.7/m2

Andrews & Lemon: Clearly recorded more native seedlings and saplings in native forest than in pines, but showed no tendency for the number of seedlings to decline with distance from the edge of the pine forest (for a distance of 100m into the pines).

Effects of insect grazing on selected species

Piggott & Steven: Examined leaf damage to Melicytus, Hedycarya and Knightia. The first two showed an accumulation of leaf damage with

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age, while the latter did not. There was a suggestion that fungal attack was associated with reduced insect damage.

Miller & Hickey: Studied interaction between fungus cover and insect grazing using Chi squared tests on Alseuosmia spp. Their results indicated that insects prefer leaves without fungus, although they didn't quite believe this.

Salisbury & Wilkie: Studied the same interaction in pukatea (Laurelia novae zelandiae), but could show no significant difference between insect attack on fungal and non-fungal leaves, although there were significant differences between individual seedlings in the amount of damage.

Lyne & Verheul: Compared insect damage to the superficially similar plants Olearia rani and Brachyglottis repanda. The histograms of frequency of damage in different classes looked different with generally higher levels of damage in the larger leaved Brachyglottis, but the difference was not significant by a variety of tests.

Arounson & Hart: Studied a variety of different species growing on the riverbank and on the ridge. They found considerable differences in the amount of damage on the two sites for all species examined as follows: Amount of insect damage: River flat > Ridge (Pseudopanax arboreus)

Ridge > River flat (Coprosma "Large leaved") Ridge = River flat (Alseuomia spp.) Ridge > river flat (Olearia rani)

The statistical significance of these results was not adequately ascer­tained. The general order of preference, according to degree of damage was: River flat: Pseudopanax arboreus > Coprosma > Olearia rani > Alseuosmia spp. Ridge: Coprosma > Pseudopanax arboreus > Olearia rani > Alseuosmia spp.

Effects of possum browsing on seedlings and saplings

Sylvester & Browne: Compared the nature of the possum damage with that caused by insects, and attempted to rank species according to degree of damage. Ranking was: Coprosma robusta > Dysoxylum spectabile > Pseudopanex arboreus > Rhopalostylis sapida >> Knightia excelsa Did not adequately sort out effects of possum "preference" and relative abundance of different seedlings.

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Effects of substrate on forest composition

Sullivan & Arnesen: Described change in forest composition according to depth of substrate (probe), in three areas. Noted differences in composition but were unable to adequately differentiate between the influence of substrate (sandy, silty, stony etc) and successional age. The probe method could be used to pick up differences between areas using 50 probes/area.

INDIVIDUAL PROJECT SUMMARIES (1983)

Tawa Population Ecology

Waugh & Murie: Categorised forest in terms of light intensity and looked at frequency of Beilschmiedia tawa seedlings and saplings in low, medium and high light intensity phases. Seedlings were most abundant in shade and saplings in high light situations — implying recruitment in gaps.

Olds & Hainsby: Distribution of B. tawa seedlings and saplings in relation to adults. Seedling abundance was not related to presence of an adult, but saplings were more abundant beyond the canopy range of the adult. More seeds shed on south and west sides of trees.

Pseudopanax arboreus — population structure/grazing

Stone & Jones: Size frequency distribution of Pseudopanax arboreus on transects away from river bank. Number of seedlings decreases from edge of river, but number of saplings and trees increases. Light favoured Pseudopanax seedlings (No mention made of frequently epiphytic nature).

Pemberton: Found relationship between stem cross-sectional area and number of leaves in Pseudopanax arboreus. Leaf counts beneath trees indicated that 3% of leaves could be stripped in one night by possums.

Van Wakeren & Dale: Leaf area, age and insect grazing damage in Pseudopanax arboreus. Most damage occured to young leaves and declined with age.

Culley: Possum damage to Pseudopanax arboreus. Found no rela­tionship between number of leaves lost and amount of bark damage, between tree size and leaf or bark damage, or between north and south sides of Webb Creek.

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Knightia excelsa — Population structure and regeneration

Fie ld : Distribution of Knightia excelsa regeneration with respect to distance from river. Both seedlings and saplings shared a clumped distribution pattern, and tended to decline with distance from river bank.

Frater & Strong: Found no relationship between the density of Knightia excelsa seedlings and distance from adult (> 10cm dbh) trees (5 trees, 10 transects).

Coriaria arborea — Population structure/successional status

Peters & Smitheram: Distribution of Coriaria arborea (and an appendix describing the remarkable effects of too much tutu wine, which can be summarised as an insatiable desire to fall flat on your face!). Tutu seedlings are clumped i.e. depart from a Poisson expectation (numbers may decline as one moves away from the river).

Hedley & Jackson: Coriaria arborea size frequency along successional gradient. Coriaria becomes less frequent and represented by larger individuals (trend not significant!) along the successional gradient. It is very rarely found in the 'climax' forest.

Pittosporum huttonianum —Successional status

Knight & Jackman: Studied Pittosporum huttonianum in successional communities. Maximum density reached before maximum basal area in succession. Early stage of succession but not a pioneer, maximum density reached when Leptospermum is c.8m tall. Seed production in relation to population age and serai position warrants further work.

N i k a u population in Webb Creek

Healy: Age structure of nikau palm population in Webb Creek with respect to aspect and canopy cover. Nikau seedling densities were c.3-5/m2 on the south side and c.l.0/m 2. on the north side in areas chosen for presence of at least one mature tree. Populations markedly clumped.

Fotherinham & H i l l : Nikau concentrated on the north-facing (sunny) slope of Webb Creek — statistically significant. Quintinia Seedling requirements

Stewart & Cole: Distribution of Quintinia serrata seedlings on tree

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ferns and on ground (Wainora track). Density per m 2 on tree ferns wae usually c. lOx that of seedlings on ground (eg transect 1: 3.22 Quintinia seedlings/m2 on Dicksonia squarrosa trunks, compared to 0.33/m 2 on the ground; elsewhere densities were lower but relative difference main­tained). Most of the seedlings 'on the ground' were actually rooted in rotting tree fern trunks.

Tree fern studies

Austin & Corbett: Investigated the population structure of Cyathea medullaris near the base of Moss Creek and in the Tarawaere Stream Valley. Discussed models of possible growth and influence they would have on size structure. Established forest areas have a large proportion of large individuals and relatively few 'young' ferns. C. medullaris colonises areas after disturbance once some vegetation has become established.

Gill & Galilee: Comparison of tree ferns with respect to seedling densities growing upon them. Densities of seedlings on the ground (2.8/m2) were similar to those on Dicksonia squarrosa (2.2/m2) and Cyathea dealbata (2.4/m2) but some species showed definite preference for tree fern trunks: Pseudopanax arboreus, Weinmannia racemosa, Carpodetus serratus, Alseuosmia macrophylla, Kunzea ericoides. (The latter species was totally absent on the ground).

Lusk & Kindley: Comparative study of Cyathea dealbata and C. medullaris as hosts for Weinmannia seedlings. Found no significant difference in seedling densities for this species between the two ferns (Means 18.5/m2 for C. medullaris; 14.5/m2 for Cyathea dealbata. Also found no significant difference in size frequency distribution of seedlings' on different ferns — i.e., survivorships of Weinmannia did not differ on the different host (Height-circumference data for both species).

Cleary & Hoyle: Altitude and tree ferns. D. squarrosa predominantly at low altitude (250m) but extending throughout, at least to 700m. Cyathea smithii (and C. medullaris) recorded only at 600m and Cyathea dealbata only below this (in sample plots on Moss Creek track).

Seedling studies (general)

Workman & Kelly: Relative distribution patterns of seedlings and saplings on the forest floor. Found more seedlings in areas with fewer saplings. Mean seedling density in areas without saplings = 11.1/m2; in areas with saplings = 6.5/m2.

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Phi l l ips : Effects of trampling on seedling populations. Could demons­trate none.

Boyd & Barnfather: Colonisation of rocky river bed by Leptospermum, Coprosma robusta, Coriaria arborea and Senecio spp. Leptospermum scoparium > Coprosma > Coriaria arborea in abundance).

Brachyglottis repanda — Distribution

Nicole & Craddock: Spatial distribution of Brachyglottis repanda (and Oleria rani). Seedlings usually found near adult plants and more abundant in light breaks (Further from adult plants when these were situated in shady places).

A C K N O W L E D G E M E N T S

The ninety six students named in the body of this report have not been individually asked for permission to quote their results. We hope that no grave injustice has been done to any one's effort and remind those involved and readers alike that the "results" presented are our interpretations of the data presented in the individual reports.

We acknowledge gratefully the help of many masters students from the Departments of Botany and Zoology who have acted as demonstrators. We also thank Richard Serra, for keeping body and soul together and providing sane comment.

R E F E R E N C E S

Nicholls J .L . 1971: Sheet 3. Coromandel. Forest Service Mapping Series 6, 1: 250,000. Forest Research Institute.

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