Mojave Desert Soils

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Mojave Desert Soils

• And Associated Plant Life

With Case Studies of the Mojave River
Floodplain, Larrea and Ambrosia Species
Preference, And Succession in the Panamint
Mountains.
suif.stanford.edu/nickolai/photos
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Overview

• General constraints of soil
• Geologic setting for Mojave river soils
• Differential plant use of soil horizons
• Plant Succession on Panamint Mountains

suif.stanford.edu/nickolai/photos
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So whats the big deal?
Well water. Poor infiltration into desert
pavement ? clay Low water table, quick
evaporation Salts, toxins ? ex black alkali
Diagram Curtesy of Arvidson, adapted from
Strahler (1963). 
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Black Alkali

• sodium clays ----hydrolyzes----gt
• sodium hydroxide ---CO2---gt sodium
  carbonate(high pH) (soil air)
• sodium carbonate ---organic matter---gt
• black crust on surface - 'black-alkali
• Sodium Dispersal and soil swelling
• In competition with clay

Swelling by exchangable sodium percentage
Picture by Allan Grogan /www.agric.nsw.gov.au/Age
du/Tocal/salinity Chart waterquality.montana
.edu/docs (After McNeal, 1968).
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Organic Matter
Flowering Acacia

• Typically, not there

Need for Nitrogen Sources Bacteria, Algae,
Legumes
http//mgordonphotography.com/images/gallery2006/0
31_lg.jpg
http//www.pbase.com/bearpaw/image/28377252
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Geologic Settingminerals and spacing of
substrate

• Alluvial fans and braided stream deposits sand,
  unconsolidated gravel
• Subsurface silt and clay
• Calcerous playa sediments
• Igneous and metamorphic ridges

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Larrea Tridentata During Peak Spring
conditions, pre-dawn water potential and midday
net photosynthetic assimilation were highest in
Larrea at the intermediate alluvial site where
soils had substantial surface and subsurface
horizons, and at the pavement site where soils
had strong surface layers but little susurface
development
Ambrosia Dumosa In contrast to Larrea, density
of Ambrosia increased with soil horizon
development, but smaller plant sizes resulted in
similar canopy volume per area and identical
pre-dawn water potential and midday net
photosynthetic assimilation across all soils
where it occurred, suggesting greater plasticity
to the transmittal of precipitation.
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www.nazflora.org/Larrea
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Larrea and its substrate
Lack of clay rich B layer, thinner soils. Larrea
Canopy height and basal diameter greatest on
young alluvial fan Post-storm plant activity
greatest at young alluvial fan Plant density
greatest at intermediate alluvial fan.
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Soil composition as important as overall
precipitation. Difference development of thick
A and B soil horizons. How much water, where is
the water going, how long does it stay there?
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Larrea Summary

• Young Alluvium and Dunes
• Intermediate Alluvium
• Older Alluvium and Pavement

www.nazflora.org/Larrea
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Succession through three stages
Ambrosia

• Youngest debris flow characterized by twelve
  species not present at the other two sites. Most
  abundant plant Lupinus Excubitus.
• Intermediate debris flow contained a significant
  number of coleogyne and lycium. Grayia dominant
  in small local pockets.
• Oldest debris flow at this and other sites
  maintained a large percentage of coleogyne
  plants.

Lupinus
Grayia
Coleogyne
www.kenbowles.net/SDwildflowers/
biology.burke.washington.edu/herbarium/
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Sources
Pearson, Krista E. The Basics of Salinity and
Sodicity Effects on Soil Physical Properties.
Adapted by Krista E. Pearson from a paper by
Nikos J. Warrence, Krista E. Pearson, and
James W. Bauder (2003). waterquality.montana.edu/d
ocs/methane/basics_highlight.shtml. Fuller,
Wallace H. Soils of the Desert Southwest. Tucson
University of Arizona Press, 1975. Stamos,
Christina L. et al. Geologic setting,
geohydrology and ground-water quality near the
Helendale Fault in the Mojave River basin,
San Bernardino County, California.
Sacramento, Calif. U.S. Dept. of the Interior,
U.S. Geological Survey. 2003. Hamerlinck, Eric
P. et al. Ecological Responses of Two Desert
Shrubs to Soil Horizon Development and
Soil Water Dynamics. Ecology, 83(3). pp 768-779.
2002. Webb, Robert H., Steiger, Turner.
Dynamics of Mojave Desert Shrub Assemblages in
the Panamint Mountains, California.
Ecology, 68(3). Pp 478-490. 1987.