1

Soil indicators to assess the

effectiveness of restoration

strategies in dryland ecosystems

Edoardo A.C. Costantini1, Cristina Branquinho2, Alice Nunes2,

Gudrun Schwilch3, Ilan Stavi4, Claudio Zucca5

1 Consiglio per la ricerca in agricoltura e l’analisi dell’economia agraria, CRA-ABP Agrobiology and Pedologi Research Centre, Firenze, Italy

2 Centre for ecology, evolution and environmental changes, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, Lisboa, Portugal

3 University of Bern, Centre for Development and Environment (CDE), Switzerland

4 Dead Sea and Arava Science Center, Ketura 88840, Israel

5 Soil Conservation and Land Management International Center for Agricultural Research in the Dry Areas (ICARDA), Amman, Jordan and Dep.

of Agriculture & Desertification Research Centre (NRD), Sassari, Italy.

edoardo.costantini@entecra.it

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In this talk

Introduction: Soil ecosystem services

Degradation, desertification, and restoration strategies

Specificities of dryland ecosystems

Soil indicators: Soil qualities and characteristics regulating soil water availability

SOM content, forms and causes of variations

Bioclimatic and biological soil quality indicators

Soil functional indicators

Conclusions

AIR QUALITY

GHG emissions

Carbon

sequestration

SUPPORT

Structures and

infrastructures

REGULATION

Regulation of the

water cycle

And of sediment

(soil erosion)

PROVISION

Biomass (food and

fiber)

Building materials

and fuel

PROTECTION

BIODIVERSITY

RESILIENCE

CULTURAL

Cultural heritage,

conservation of

archaeological

finding

Soil ecosystem services in drylands

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Pedoclimate, vegetation, and desertification

Drylands: shrublands (24%),

savannas (15%),

forests (8%),

and grassland (13%)

Soil restoration strategies

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Local climate, vegetation, and soil: the missing link

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Specificities of dryland ecosystems: vegetation

structure and dynamic 1) Spatial variability of dry ecosystems: 1st and 2nd dimensions

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Patches (fertility islands) and inter-patch spaces

(herbaceous, biological crusts, bare soil)

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Biological and mineral crusts

Source-sink ecosystems

Sink Source

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3rd dimension: shallow and

wide root systems in savanna

like woodlands: herbs, shrubs

and trees

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Depth of root systems in herbs, shrubs and trees

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4th dimension: time variability of dry ecosystems

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Soil indicators of soil quality

The soil-quality concept integrates inherent soil quality and

dynamic soil quality (De La Rosa and Sobral, 2008)

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Specific soil functions considered for several soil

quality issues (De La Rosa and Sobral, 2008)

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Soil attributes which may be used as indicators of

soil quality (Soil Quality Institute, 2015)

Physical Properties

• Aggregate Stability

• Available Water Capacity

• Bulk Density

• Infiltration

• Slaking

• Soil Crusts

• Soil Structure and Macropores

Chemical Properties

• Reactive Carbon

• Soil Electrical Conductivity

• Soil Nitrate

• Soil pH

Biological Properties

• Earthworms

• Particulate Organic Matter

• Potentially Mineralizable Nitrogen

• Soil Enzymes

• Soil Respiration

• Total Organic Carbon

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The most prominent impacts of SLM are related to

water

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Soil conservation and the hydrological cycle:

the Green water / Blue water ratio

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Green water balance

+ water inputs

+ soil water storage

- water outputs

- soil water tension

- toxicity for plants

Water input

Drivers

Soil qualities

Functional soil characteristics

Rainfall, Irrigation Infiltration capacity Infiltration rate (texture, structure, stoniness,

cracks)

Groundwater Deep recharge Capillary rise (texture, structure, stoniness)

Surface and subsurface

flows

Surface recharge Topography, natural and artificial channels,

ditches

Soil water storage

Soil volume

Porosity

Texture, structure, bulk density, stone volume

and weathering

Root penetration Root explorable volume of horizon, Rooting

depth of profile

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Soil qualities and characteristics

regulating soil water availability

Water output

Drivers

Soil qualities

Functional soil characteristics

Evapotranspiration Surface cover Mulch, stoniness, crusts

Runoff Surface morphology Slope, mulch, stoniness, rockiness,

crusts, micro low-high relief, natural and

artificial channels, ditches

Drainage (rock nature, artificial

piping)

Permeability Hydraulic conductivity

Soil water tension

Soil-water adhesion

Soil water holding capacity

Soil water tension curve

Lithology, irrigation Salinity Electrical conductivity, soluble salts

Toxicity for plants

Natural background,

pollution

Soil water composition Pollutant contents and availability

Anoxia Oxygen availability Air capacity

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Soil water availability is tricky!

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Soil organic matter is a key factor for

green water availability

Water input

Rainfall, Irrigation Infiltration capacity Infiltration rate (structure, cracks)

Groundwater Deep recharge Capillary rise (structure)

Water output

Evapotranspiration Surface cover Mulch, crusts

Runoff Surface morphology Mulch, crusts

Drainage (rock nature, artificial

piping)

Permeability Hydraulic conductivity

Water storage

Soil volume Porosity Structure, bulk density

Root penetration Root explorable volume of horizon, Rooting depth of

profile

Soil water tension

Soil-water adhesion Soil water retention Soil water tension curve

Lithology, irrigation Salinity Electrical conductivity

Soil water composition

Natural background, pollution Soil water composition Pollutant content and availability

Anoxia Oxygen availability Air capacity

SOM and soil ecosystem

services:

- green water

- hydrological cycle

- air quality

- biodiversity

Most of European soils have less than 2% of SOC in

the first 30 cm (source: JRC, 2010)

SOC (dag kg-1) and main land uses of Italy

arable lands meadows forests

Land Uses

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.8

3.0

3.2

SO

C C

on

tent (d

ag k

g-1

)

Mean

Mean±0.95 Conf. Interval

Organic carbon profile and land use, the

stratification ratio (Franzluebbers, 2002)

Organic carbon

0

10

20

30

40

50

60

0 1 2 3 4

(%)

cm

Macchia

Prato

Coltivato

Soil organic matter fractions and degradation

ab

b

a

0

2

4

6

8

10

12

GR NO NAT

pp

m

Labile organic carbon (LOC) P = 0.0067

Labile organic carbon (reactive carbon)

mild potassium permanganate (KMnO4) oxidation method (Weil et al., 2003) 31

Carbon lability

b

a

b

0

0.005

0.01

0.015

0.02

0.025

0.03

GR NO NAT

)%/%

(

Lability (L) P < 0.0001

Lability (L): L = (LOC) / (non-LOC) [%/%] (Blair et al., 1995) indicates the ratio

between labile organic carbon and non-labile organic carbon (where the non-LOC

fraction was calculated by subtracting the LOC from the total SOC)

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Soil organic matter content is a dynamic

property

SOC variations and climate

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dry xeric xeric ustic udic

Udometric Regimes

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

SO

C C

on

tent (d

ag k

g-1

)

Mean

Mean±0.95 Conf. Interval

thermic mesic

Thermometric Regimes

1.4

1.5

1.6

1.7

1.8

1.9

2.0

SO

C C

on

tent (d

ag k

g-1

)

Mean

Mean±0.95 Conf. Interval

200 0 200100 Km

not arables

-109 - 0

0 - 8

8 - 115

Index of Climate Impact on SOC Variations in Arable Lands

Mean Ic Indexes (%):

•34.5 in meadows;

•16.8 in arable lands;

•11.6 in forests.

Index of climatic influence on SOC variations

between the years 1961-1990 and 1991-2006

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The soil aridity index Number of dry days per year SAI = 75.363 + 6:874 MAT -0.064 TAP * 0:299 AWC

0102030405060708090

100

<80 81-115 >115

%

n

A

B

C

D

E

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Soil aridity index: validation at the detailed scale

Methodology

•Collect soil for each main

horizon of the profile, to assess

soil bulk density, granulometry,

organic matter content

•Fill a form for site

geomorphology and pedology

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ID 1 2 3 4

AridityClass Drysubhumid Semiarid Semiarid

AridityIndex 0,56 0,51 0,48 0,42

Soil Luvisoil Litosoil Luvisoil Litosoil

Slope(%) 10 60 5 5

Prec(mm/yr) 634 576 579 521

Temp (°C) 16 15,9 16,3 17

Tree cover (%) 10 90 10 30

Woody cover (%) 25,6 77,9 12,8 3,8

Bare soil(%) 17,4 28,7 27,3 14,9

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y = 4.2128x + 115.31 R² = 0.6219

0.00 0.50 1.00 1.50 2.00 2.50 3.00

114

116

118

120

122

124

126

128

130

SAI and SOC

1) Biochemical soil attributes

Corg total organic carbon, g Ckg-1 soil;

Cext total extractable carbon, g C kg-1 soil;

Cha + fa = humic and fulvic acid carbon g C kg-1 soil;

DH humification degree, mg Cha + fa mg Cext-1 100

Cmic microbial biomass carbon, mg C kg-1 soil;

Ccum cumulative respiration, C–CO2 total production at 32nd day,

mg C–CO2 kg-1 soil;

qCO2 metabolic quotient, (mg C-CO2) (mg Cmic kg-1 soil)-1 h-1;

K rate constant of carbon mineralization (Ccum Corg-1)*100;

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Biological indicators

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2) the soil biological fertility index IBF (Mocali and

Benedetti, 2009)

Parameters Range

1 2 3 4 5 Organic matter (%) <1 1 – 1.5 1.5 – 2 2 – 3 >3 Basal respiration (ppm) <5 5 – 10 10 – 15 15 – 20 >20

Cumulative respiration (ppm) <100 100 – 250 250 – 400 400 – 600 >600

Microbial carbon (ppm) <100 100 – 200 200 – 300 300 – 400 >400

Metabolic quotient >0.4 0.3 – 0.4 0.2 – 0.3 0.1 – 0.2 <0.1

Mineralization quotient <1 1 – 2 2 – 3 3 – 4 >4

The sum of single values obtained for the six parameters (the minimum is 6 and the maximum 30) in a given soil establishes the class of biological fertility – IBF RANGE

Biological fertility class I

II

III

IV

V

alarm stress medium good high

Range 6 7-12 13-18 19-24 25-30

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IBF map of Po Plain

in the Lombardy region

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3) the soil biological quality index QBS-ar (Parisi; 2001)

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EPIEDAPHON - EMIEDAPHON

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EUEDAPHON

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Soil Biological Quality index: methods

• The QBS index is based on microarthropod groups present in a soil

sample.

• Each type found in the sample receives a score from 1 to 20 (eco-

morphological index, EMI), according to its adaptation to soil

environment.

• The QBS index sums up these scores, thereby characterizing the

microarthropod community of the sample being studied.

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Recovery of soil biology after

deep earthworks

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Soil functional indicators,

the LFA (Tongway and Hindley, 2004)

The LFA uses semi-

quantitative field-based

indicators to evaluate

the soil surface

condition at the hillslope

scale, targeting surface

properties that control

nutrient cycling and

infiltration processes,

such as surface cover

by perennial plants,

litter cover and degree

of decomposition,

surface roughness, soil

texture, and surface

crust stability

Indicator stability, SI; Infiltration/Runoff, IR

Nutrient Cycling, NC;

N. of classes SI IR NC

Rainsplash Protection 5 X

Perennial Vegetation Cover 4 X X

Litter cover 10 X X X

Litter origin 2 X X

Litter decomposition 4 X X

Cryptogam Cover 5 X X

Crust Brokenness 5 X

Erosion Type and Severity 20 X

Deposited Materials 4 X

Surface Roughness 5 X X

Surface resistance to disturbance 5 X X

Soil slaking 5 X X

Texture 4 X

Conclusions

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1. Some of the many soil characteristics affecting green water

availability are related to soil organic matter

2. SOM is a key attribute for many ecosystem functionalities

3. SOM is deeply affected by local climate and management

4. SOM functional forms, and related biological activities and

organisms, are still far from being well understood and

characterized, nevertheless, there are some new indicators

5. Effectiveness of restoration strategies can be estimated by

means of qualitative soil surface and vegetation indicators

6. Sound, easy and reliable indicators linking climate,

vegetation and soil functions at the detailed scale are still few!!

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Thank you for your attention!