multiscale variability of soil aggregate stability
TRANSCRIPT
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Multiscale variability of soil aggregate stability: implications
for rangeland hydrology and erosion
Mike DuniwayJeff HerrickKen Spaeth
Nichole BargerJustin Van Zee Jayne Belnap
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Why soil aggregate stability?
•
Soil surface characteristics control capture and retention of water and nutrients
•
Soil aggregate stability is related to soil erodibility & infiltration capacity, both of which are:–
highly variable
in space and time
–
difficult to measure
“…“… soil aggregate stability soil aggregate stability …… has been demonstrated to have a has been demonstrated to have a strong relationship with interrill erosionstrong relationship with interrill erosion”” (Blackburn & Pierson, 1994)(Blackburn & Pierson, 1994)
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Soil stability kit(2) Immerse in dI water.(2) Immerse in dI water.
(3) Record slaking in 1(3) Record slaking in 1stst
5 min.5 min.
(4) Wet sieve 5x.(4) Wet sieve 5x.
(5) Rate sample on a(5) Rate sample on a
scale from 1 to 6.scale from 1 to 6.
(1) Collect 6(1) Collect 6--8 mm8 mm--diameterdiameter sample from surface and 20sample from surface and 20--
25mm depth (1 sample/sieve). 25mm depth (1 sample/sieve). Herrick et. al 2001. Catena 44: 27-35.
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Soil stability kit: interpretation
Stability class
Criteria for assignment to stability class (for Standard Characterization)a
1
50 % of structural integrity lost within 5 seconds of insertion in water.
2
50 % of structural integrity lost 5 - 30 seconds.
3
50 % of structural integrity lost 30 - 300 seconds after insertion OR <10% of soil remains on sieve after 5 dipping cycles.
4
10 - 25% of soil remains after 5 dipping cycles.
5
25 - 75% of soil remains after 5 dipping cycles.
6
75 - 100% of soil remains after 5 dipping cycles.
Soil erosionSoil erosion:: high values high values indicate lower indicate lower erodibilityerodibility
Water infiltrationWater infiltration: : high values high values may be associated with may be associated with higher infiltration rates.higher infiltration rates.
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Relatively static factors that affect aggregate stability
Regional climate
SOM (stable fraction, turnover
time >15 yrs)Soil texture
Mineralogy
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Relatively static factors that affect aggregate stability
Mean Annual Precipitation (mm)150 200 250 300 350 400 450
Soil
Stab
ility
Cla
ss
0
1
2
3
4
5
6
r = 0.247p = 0.055
Regional climate
NRCS NRI Data from 2003-06
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Relatively static factors that affect aggregate stability
Mean Annual Precipitation (mm)
200 250 300 350 400 450
Soil
Stab
ility
Cla
ss(N
o C
anop
y)
1
2
3
4
5
6
r = 0.623p = 0.041
Regional climate
NRCS NRI Data from 2003-06
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Relatively static factors that affect aggregate stability
% Silt0 10 20 30 40 50 60
Soil
Stab
ility
Cla
ss
0
1
2
3
4
5
6
r = 0.254p = 0.049
Soil texture
NRCS NRI Data from 2003-06
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Relatively static factors that affect aggregate stability
% OM0.0 0.5 1.0 1.5 2.0 2.5 3.0
Soil
Stab
ility
Cla
ss
0
1
2
3
4
5
6
r = 0.349p = 0.006
SOM (stable fraction,
turnover time >15 yrs)
NRCS NRI Data from 2003-06
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Dynamic factors that affect aggregate stability
Annual, inter annual climate variability
SOM (active fraction, 1-2 yr
turnover)Plant biomass/
production
Plant communitycomposition
Bare ground & canopy cover
Soil biota, Biological soil crusts
Disturbance
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Dynamic factors that affect aggregate stability
% Bare Ground0 20 40 60 80 100
0
1
2
3
4
5
6
r = 0.477p < 0.001
% Canopy Cover0 20 40 60 80 100
Soil
Stab
ility
Cla
ss
0
1
2
3
4
5
6
r = 0.500p < 0.001
NRCS NRI Data from 2003-06
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How do we look at in context of hydrology and erosion?
•
Auto correlated with many other plot attributes at larger scales
•
Falsely conclude not important for predicting site hydrology and erosion characteristics
Static + Dynamic Axis
-3 -2 -1 0 1 2 3
Soil
Stab
ility
Axi
s
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Canonical Corr = 0.650
p< 0.001
NRCS NRI Data from 2003-06
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•
Disturbance & Patchiness
Distance (m)
0-5 5-15 > 40
Soil
Stab
ility
Rat
ing
0
1
2
3
4
5
6
Crown and Ditch Two Track
How do we look at in context of hydrology and erosion?
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How do we look at in context of hydrology and erosion?
Protected
Soil
Stab
ility
Rat
ing
0
1
2
3
4
5
6
7
Unprotected
•
Protected vs. Unprotected–
Protected not important for raindrop impact
–
Protected often not important for overland flow
•
Site average not always reflective of importance
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How do we look at in context of hydrology and erosion?
•
Non-linear response
Soil Stability Class
1 2 3 4 5 6 7
Sedi
men
t (g
m-2
)
10-1
100
101
102
103
104
10 min30 min
R2 = 0.58p = 0.002
R2 = 0.41p = 0.014
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How do we look at in context of hydrology and erosion?
•
Ideal for heterogeneous systems?
•
Incorporate spatial distribution of: –
Soil stability measures
–
Vegetation measures–
Other soil & site properties
•
With:–
Multiscale runoff and erosion measures
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How do we look at in context of hydrology and erosion?
•
And…………incorporate field data in spatially explicit analysis
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Questions?