2/20/2013
Impact of Wind Erosion on
Soils in Arid and Semi-arid
Landscapes
Ted M. Zobeck, Research Soil Scientist
USDA, Agricultural Research Service
Lubbock, TX
Arid and Semi-Arid Soil Pedogenesis: Unraveling the Linkages Among Soil Genesis,
Soil Mineralogy, and Quaternary Landscape Evolution: In Honor of B. L. Allen
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In Honor of Dr. B. L.
Allen, Renowned
Pedologist,
Mineralogist, Teacher,
Mentor, TWERP, and
Friend
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Presentation Overview
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Defining the Scope
Soil Formation
Aeolian Processes
Characteristics of sediment
Local Effects
– Coppice dunes, islands of fertility
• Regional/Global Effects
– Proximity to source, loess, Terra Rossa Soils
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Aeolian deposits occur over much of the globe. Their
origin and subsequent development widely varies. Today
I will focus on aeolian processes in arid and semi-arid
dryland regions.
Source FAO, 2002
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So how do aeolian processes
affect soils?
First, let’s have a very brief
review of soil formation
processes….
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Processes of Soil Formation
Remember - Soil = f(climate, organisms, parent material, topography, and time)
Factors of Soil Formation, Hans Jenny, 1941
Roy Simonson’s conceptual model
of soil formation (1959)
Source: Lesley Dampier,
SoilWeb, Univ. Brit. Columbia
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Wind erosion often occurs when soils are
bare, loose, dry and subjected to erosive
winds.
Most prevalent in coarse-textured soils.
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Wind erosion is active today!
Meadow, Texas September 3, 2011
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Effect of sampling height on particle
size
Mean diameter varied from 100 µm at 0.15 m to 50 µm at 2 m
Zobeck and Fryrear, 1986a
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This impacts transport of minerals,
nutrients, organic matter, microbes…
Mean nutrient content and enrichment ratios for dust caught at
0.15 m to 2.0 m for 6 dust storms in west Texas
Na
K
Ca
Mg
CEC
OM
Amount
0.06
1.06
7.01
1.19
9.34
4.18
Enrichment
Ratio
2.1
1.6
2.0
1.2
2.1
2.0
Nutrients in cmole (+)/kg and OM in g/kg
From Zobeck & Fryrear, 1986b
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Removal can be quite large…
During a field campaign from 1989-1997 at Big
Spring, Texas, observed soil loss due to wind erosion
on an agricultural field varied from about 40 to 290
Mg/Ha/Yr
The field was kept bare, smooth, and erodible.
Van Pelt & Zobeck, 2004
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Creep and Saltation material is usually
trapped near the source and impacts
local vegetation and surface features
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Erosion of patchy vegetation in grasslands/shrublands
has significant impacts on soil properties and
redistribution of nutrients and sediment.
(Ravi at al., 2010)
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We observed differences in soil
properties under plants and
openings
• Compared with inter-shrub areas, the shrub
patches had a higher soil porosity, infiltration
capacity, water-holding capacity, hydraulic
conductivity, structural stability, and organic
matter content, and lower bulk density. (Stavi
et al, 2009).
• In another study, surface N and C were
significantly greater for soil under plants than
soil from openings. (Hook et al., 1991)
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Let’s look at material that moves greater distances…
Where does it all go?
Well….That depends…..
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Wind Direction and Sediment Barriers
Have and Impact
A recent study by Hirmas and Graham (2011)
presented evidence for how the Fry
Mountains of California act as a topographic
‘baffle’ against the prevailing wind and
trapping aeolian sediment.
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Studies have discovered how distance from
the source affects aeolian soils in many
ways
A 390 km transect in west Texas showed
decreasing sand size with distance from the
hypothesized Pecos River source (E. M. Seitlheko
[with B.L. Allen], 1975)
There have been many other studies of the effects
of proximity to a source region when studying soils
with aeolian parent materials, particularly loess
soils.
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But what about loess?
Much of the world’s loess occurs in mid-latitudes
associated with glaciation…
(Thomas and Wiggs, 2008)
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Desert Loess Formation
Tsoar and Pye, 1987
• Loess mainly medium silt size transported near
the surface and so is relatively close to source
• Availability of silt source and wind needed
• Suitable dust trap very important
– Topographic obstacles
– Moist ground
– Vegetated surfaces
• Dust blown during glacial periods from certain
deserts (Sinai, Soviet Central Asia, China)
accumulated loess in neighboring semi-arid
areas
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Desert Loess Formation
Tsoar and Pye, 1987
• Other deserts mainly lacked traps
• Other deserts lack silt source
• During most of Holocene deposition rates
just too low to form loess (lack landscape
stability).
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Finer Dust Impacts Many Areas
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Global 10 to over 200 t km-2 yr-1 (Pye, 1987)
Israel 57-217 t km-2 yr-1(Yaalon and Ganor, 1975)
Australia 5-10 t km-2 yr-1 (Tiller et al., 1987)
Nigeria 137-181 t km-2 yr-1 (McTainsh and Walker,
1982)
Central and west (Edwards Plateau)Texas 12 t km-2 yr-1
(Rabenhorst et al, 1984)
SHP West Texas 77-103 t km-2 yr-1 (Crabtree, 2005)
S. Nevada and S. California 4 to 30 t km-2 yr-1 (Reheis
and Kihl, 1995).
SW California 79 4 to 30 t km-2 yr-1 (Hirmas and
Graham, 2011)
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Dust affects distant ecosystems
and soils
• Saharan dust has been
identified as the most
important parent
material of soils of
Caribbean Islands and
Florida Keys (Muhs, et
al., 1990)
• Hawaiian rain forests
receive nutrients from
Asia and sustains the
productivity of these
rain forests (Chadwich
et al, 1999).
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Dust affects distant ecosystems
and soils
• ‘Terra Rossa’ soils of Mallorca, Spain
developed from African dust (Muhs, et al.,
2010)
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Aeolian processes do indeed
impact soil genesis, mineralogy,
and landscape evolution in arid
and semi-arid regions (and far
beyond).
We have much more to learn and
invite you to join the fun.
www.aeolianprocesses.org
Find us on FaceBook
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