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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.
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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!