Wind and Water Erosion under Alternate Land Uses: Insights from Ongoing Research

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Wind and Water Erosion under Alternate Land Uses
Insights from Ongoing Research at the Santa Rita
Experimental Range
David D. Breshears1,2 Jason P. Field1,, Chris B.
Zou1 and
Jeffrey J. Whicker3
1 School of Natural Resources, University of
Arizona 2 Institute for the Study of Planet
Earth Department of Ecology and Evolutionary
Biology, University of Arizona 3 Health Physics
Measurements Group Health, Safety, and Radiation
Protection Division, Los Alamos National
Laboratory
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The Importance of Wind Erosion
Wind Erosion
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The Importance of Wind Erosion
Wind Erosion
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The Importance of Wind Erosion
Wind Erosion
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The Importance of Wind Erosion
Wind Erosion
Peters et al. 2006 BioScience
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On Saturday, this area of Texas had a dust storm
pass through. The sky turned brown, but there was
not much deposition of the fine material.Surface
winds had gusts well into the 30 mph range. It
was sort of a nice teaser for your talk.
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Competing contaminant transport mechanisms?
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Conceptual Framework
Canopy
Intercanopy
Ecosystem Properties Dynamics
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Conceptual Framework
Canopy
Intercanopy
Ecosystem Properties Dynamics
Climate Variation Change
Land Use Management
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Contaminant Transport and Risk
Vegetation Dynamics and Biogeochemistry
Geomorphology
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Time Scales
Paleo
Annual
Disturbance Event
Event
Water Erosion
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Time Scales
Paleo
Annual
Disturbance Event
Event
Water Erosion
Wind Erosion
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Dryland Ecosystems
Barren / Disturbed
Agricultural
Grassland
Shrubland
Woodland
Forest
Water Erosion
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Dryland Ecosystems
Barren / Disturbed
Agricultural
Grassland
Shrubland
Woodland
Forest
Water Erosion
Wind Erosion
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Big Spring Number Eight (BSNE) Dust Samplers
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Breshears et al. Geomorphology in review
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Breshears et al. Geomorphology in review
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Breshears et al. Geomorphology in review
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Breshears et al. Geomorphology in review
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Breshears et al. Geomorphology in review
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Dimensions

• Water erosion
• Horizontal Fluxes

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Dimensions

• Water erosion
• Horizontal Fluxes
• Wind erosion
• Vertical and Horizontal Fluxes

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Footprint
Water erosion Often bordered
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Footprint
Water erosion Often bordered
Wind erosion Usually not bordered
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Common Erosional Processes
Detachment
Suspension
Transport
EROSION
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Common Erosional Processes
Detachment
Suspension
Transport
EROSION
Loss
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Common Erosional Processes
Detachment
Suspension
Transport
EROSION
Loss
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Erosion
Wind Erosion
Water Erosion
1-m wide gate
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Horizontal Transport
Gate rotates opening into wind
Wind-driven transport
Water-driven transport
1-m wide gate
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Study Sites
Shrubland
Grassland
Forest
Chiuahuan Desert Shrubland
Ponderosa Pine Forest
Shortgrass Steppe
Precipitation (mm)
300
370
500
Ground cover ()
66 (80)
79 (72)
98 (50)
Soil texture
Sand
Silt loam
Clay
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Soil Erosion Drivers
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• Problems
• Both contribute to total erosion rates
• No simultaneous field measures
• Relative magnitudes importance?

?
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• Problems
• Both contribute to total erosion rates
• No simultaneous field measures
• Relative magnitudes importance?

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• Objectives
• Measure wind water erosion simultaneously
• Compare temporal dynamics of both processes
• Evaluate resource redistribution potential

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Measurements vs. Models
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Wind-associated Measurements
Transport
Bagnold samplers- Horizontal flux
Weather stations
Erosion
1 and 3 m TSP samplers- Vertical flux
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Water-associated Measurements
-3m x 10m plots -Rainfall simulation of 60
mm/hr - measure runoff and sediment yield -3
replicate plots per site
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Transport
Erosion
Water
Wind
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Wind Erosion Temporal variation
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Wind Transport Spatial variation
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Event-based annual projections
Field Data
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Event-based annual projections
Field Data
Define erosion event threshold
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Event-based annual projections
Field Data
Define erosion event threshold
Determine events during sampling and multi-year
periods
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Event-based annual projections
Field Data
Define erosion event threshold
Determine events during sampling and multi-year
periods
Scale flux measurements
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Annual Erosion Projections
Water Erosion
Sediment yield (kg m-2 mm-1)
Rainfall rate gt infiltration rate
Rainfall amount per year greater than
threshold from multiyear data
ERwaterSYwater x rain/yr gt threshold
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Annual Erosion Projections
Water Erosion
Wind Erosion
Sediment yield (kg m-2 mm-1)
Soil flux (g/d/m2)
Rainfall rate gt infiltration rate
7 m/s
measurements gt 7 m/s during sampling and
from multiyear data
Rainfall amount per year greater than
threshold from multiyear data
gt 7 m/s(multiyear)

SFwind x
ERwind
ERwaterSYwater x rain/yr gt threshold

gt 7 m/s(sampling)
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Erosion
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Erosion
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Annual Transport Projections
Water Transport
Wind Transport
Sediment yield (kg m-1 mm-1)
Soil flux (g/d/m1)
Rainfall rate gt infiltration rate
7 m/s
measurements gt 7 m/s during sampling and
from multiyear data
Rainfall amount per year greater than
threshold from multiyear data
gt 7 m/s(multiyear)

SFwind x
TRwind
TRwaterSYwater x rain/yr gt threshold

gt 7 m/s(sampling)
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Transport
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Transport
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Shrubland
Grassland
Forest
Hypotheses
Wind
Water
Precipitation L M H
Near-surface wind velocity M H L
Ground Cover L M H
Mean bare patch size H M L
Soil clay content L H M
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Shrubland
Grassland
Forest
Hypotheses
Erosion Linear Scale
Wind
Water
Precipitation L M H
Near-surface wind velocity M H L
Ground Cover L M H
Mean bare patch size H M L
Soil clay content L H M
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Shrubland
Grassland
Forest
Hypotheses
Erosion Linear Scale
Wind
Water
Precipitation L M H
Near-surface wind velocity M H L
Ground Cover L M H
Mean bare patch size H M L
Soil clay content L H M
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Shrubland
Grassland
Forest
Hypotheses
Erosion Linear Scale
Wind
Water
Transport Log Scale
Precipitation L M H
Near-surface wind velocity M H L
Ground Cover L M H
Mean bare patch size H M L
Soil clay content L H M
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Shrubland
Grassland
Forest
Hypotheses
Erosion Linear Scale
Wind
Water
Transport Log Scale
Precipitation L M H
Near-surface wind velocity M H L
Ground Cover L M H
Mean bare patch size H M L
Soil clay content L H M
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Shrubland
Grassland
Forest
Hypotheses
Erosion Linear Scale
Wind
Water
Transport Log Scale
Precipitation L M H
Near-surface wind velocity M H L
Ground Cover L M H
Mean bare patch size H M L
Soil clay content L H M
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Shrubland
Grassland
Forest
Hypotheses
Erosion Linear Scale
Wind
Water
Transport Log Scale
Precipitation L M H
Near-surface wind velocity M H L
Ground Cover L M H
Mean bare patch size H M L
Soil clay content L H M
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Sediment Check Dam

• Three undisturbed plots
  (50 x 50 m)
• Each plot contains
• Six self-orienting dust samplers
• A pair of sediment check dams
  (bordered 3 x 10 m and unbordered)

• Sediment collection
• Sample collection every 7 14 days
• Sediment oven-dried at 60ºC

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Summer monsoon
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WIND vs. WATER Other Dryland Ecosystems?
WIND
WATER
Shrubland Grassland Forest
Breshears et al. 2003
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Soil Erosion Issues and Uncertainties
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Soil Erosion Issues and Uncertainties
Hydrological Bias?
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Soil Erosion Issues and Uncertainties
Hydrological Bias?
Disturbance?
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Soil Erosion Issues and Uncertainties
Hydrological Bias?
Disturbance?
Climate Change?
Walker and Steffen 1997
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• WIND erosion can dominate WATER erosion
  in semiarid systems
• Wind erosion appears to be more important
  than suggested in the literature

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• WIND erosion can dominate WATER erosion
  in semiarid systems
• Wind erosion appears to be more important
  than suggested in the literature
• Simultaneous measures of both processes are
  needed to
• Improve model predictions
• Determine relative magnitudes and importance
• Address potential ecological implications

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Wind Erosion Graze Small increase Fire Large
increase
Field et al. - in prep
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Wind Erosion Graze Small increase Fire Large
increase
Water Erosion Graze Small increase Fire Large
increase
Field et al. - in prep
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Field et al. - in prep
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Variation with woody plant cover and percent bare
soil
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Variation with woody plant cover and percent bare
soil Wind erosion can exceed water erosion
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Variation with woody plant cover and percent bare
soil Wind erosion can exceed water
erosion Ecologically important process?
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Redistribution
Runoff from bare patches becomes runon to
herbaceous patches
Runon ( mm )
Precipitation ( mm)
Reid et al. 1999 Soil Sci. Soc. J. Am.
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Experimental Design
R
R
R
R
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Drought-induced Changes
Forest Cover
Allen Breshears 1998 - PNAS
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Post-fire erosion
Johansen et al. 2001 - Hydro. Proc.
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Post-fire erosion
Johansen et al. 2001 - Hydro. Proc.
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Post-fire erosion
Johansen et al. 2001 - Hydro. Proc.
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Applications
Contaminant Transport and Risk
Vegetation Dynamics and Biogeochemistry
Geomorphology