Multiscale variability of soil aggregate stability ...
Transcript of Multiscale variability of soil aggregate stability ...
Multiscale variability of soil aggregate stability: implications
for rangeland hydrology and erosion
Mike DuniwayJeff HerrickKen Spaeth
Nichole BargerJustin Van Zee Jayne Belnap
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)
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.
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.
Relatively static factors that affect aggregate stability
Regional climate
SOM (stable fraction, turnover
time >15 yrs)Soil texture
Mineralogy
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
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
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
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
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
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
How do we look at in context of hydrology and erosion?
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Auto correlated with many other plot attributes at larger scales
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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?
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
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Site average not always reflective of importance
How do we look at in context of hydrology and erosion?
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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
How do we look at in context of hydrology and erosion?
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Ideal for heterogeneous systems?
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Incorporate spatial distribution of: –
Soil stability measures
–
Vegetation measures–
Other soil & site properties
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With:–
Multiscale runoff and erosion measures
How do we look at in context of hydrology and erosion?
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And…………incorporate field data in spatially explicit analysis
Questions?