Desert soils - Arid Zone Geomorphology - page 122

Videla (1991) described a Patagonian landscape of shrub
mounds and mound interspaces. Beneath shrub mounds,
total nitrogen, organic carbon, electrical conductivity, ex-
changeable sodium percentage, exchangeable cation lev-
els and infiltration rates were significantly higher than in
interspace soils. Rostagno et al. inferred that erosion dom-
inates in interspace areas while accumulation promotes
soil evolution within the shrub mounds. Similar mounded
topography, with mounds 3-5 m long and 1-3 m wide,
and a relief of about 6.4 cm, was reported from arid aca-
cia shrubland in Western Australia by Mott and McComb
(1974). Once again the mound soils had higher organic
carbon and total nitrogen levels. Moisture characteristics
for the two soils were very similar, but a hardpan was
located typically 10 cm deeper beneath mounds, so that
soils there were overall about 16 cm deeper than those
of the mound interspace. The greater soil depth thus pro-
vided a greater reservoir of soil moisture to support the
mound vegetation.

Al-Qinna, M.I. and Abu-Awwad, A.M. (1998) Infiltration rate
measurements in arid soils with surface crust. Irrigation Sci-
ence , 18 , 83-89.
Aranibar, J.N., Anderson, I.C., Ringrose S. and Macko, S.A.
(2003) Importance of nitrogen fixation in soil crusts of south-
ern African arid ecosystems: acetylene reduction and sta-
ble isotope studies. Journal of Arid Environments , 54 , 345-
358.
Assouline, S. (2004) Rainfall-induced soil surface sealing: a
critical review of observations, conceptual models, and solu-
tions. Vadose Zone Journal , 3 , 570-591.
Aumont, O., Bopp, L. and Schulz, M. (2008) What does tempo-
ral variability in Aeolian dust deposition contribute to sea-
surface iron and chlorophyll distributions? Geophysical Re-
search Letters , 35 , DOI: 10.1029/2007GL031131.
Azua-Bustos, A. (2008) A first glance at the microenvironmen-
tal conditions allowing the colonization of quartzes by hy-
polithic microorganisms on the Atacama Desert, Chile. As-
trobiology , 8 , 427.
Belnap, J. (2006) The potential roles of biological soil crusts
in dryland hydrologic cycles. Hydrological Processes , 20 ,
3159-3178.
Belnap, J. and Gardner, J.S. (1993) Soil microstructure in soils
of the Colorado Plateau: the role of the cyanobacterium Mi-
crocoleus vaginatus . Great Basin Naturalist , 53 , 40-47.
Belnap, J. and Gillette, D.A. (1997) Disturbance of biological
soil crusts: impacts on potential wind erodibility of sandy
desert soils in southeastern Utah. Land Degradation and De-
velopment , 8 , 355-362.
Belnap, J. and Gillette, D.A. (1998) Vulnerability of desert bi-
ological soil crusts to wind erosion: the influences of crust
development, soil texture, and disturbance. Journal of Arid
Environments , 39 , 133-142.
Belnap, J. and Lange, O.L. (eds) (2001) Biological Soil Crusts:
Structure, Function, and Management , Ecological Studies
150, Springer, Berlin, 503 pp.
Belnap, J., Phillips, S.L. and Smith, S.D. (2007) Dynamics of
cover, UV-protective pigments, and quantum yield in biolog-
ical soil crust communities of an undisturbed Mojave Desert
shrubland. Flora , 202 , 674-686.
Belnap, J., Prasse, R. and Harper, K.T. (2001) Influence of bio-
logical soil crusts on soil environments and vascular plants,
Chapter 21, pp. 281-300, in Biological Soil Crusts: Struc-
ture, Function, and Management (eds J. Belnap and O.L.
Lange), Springer, Berlin, 503 pp.
Ben-Hur, M. and Lado, M. (2008) Effects of soil wetting con-
ditions on seal formation, runoff, and soil loss in arid and
semi-arid soils - a review. Australian Journal of Soil Re-
search , 46 , 191-202.
Berkeley, A., Thomas, A.D. and Dougill, A.J. (2005) Cyanobac-
terial soil crusts and woody shrub canopies in Kalahari range-
lands. African Journal of Ecology , 43 , 137-145.
Bhatnagar, A. and Bhatnagar, M. (2005) Microbial diversity in
desert ecosystems. Current Science , 89 , 91-100.
Bowker, M.A., Miller, M.E., Belnap, J. et al. (2008) Prioritizing
conservation efforts through the use of biological soil crusts

7.7 Conclusions

We still have much to learn about desert soils. In many
ways, they differ from the soils of wetter areas both in
origin and development, and in their present-day role
in landscape hydrology and geomorphology. Given the
many possible forms of anthropogenic climate change
presently underway and the mounting pressure from a
burgeoning world population, it is important that more
attention be paid to the understanding and management
of dryland soils. Some have already envisaged elevated
levels of soil loss under enhanced greenhouse effect en-
vironmental scenarios (e.g. see Dregne, 1990). Chang-
ing temperature, rainfall and other climatic conditions in
coming decades have the potential to cause changes in
some of the surface properties discussed in this chap-
ter, which may ripple through many linked environmental
processes, driving significant change in the world's dry-
lands. To understand the kinds of changes that might arise
and to support the development of management policy
and practice, we need to develop a deeper knowledge of
the vulnerability or resilience of the distinctive dryland
features considered here.

References

Adams, J.A., Stolzy, L.H., Endo, A.S. et al. (1982) Desert soil
compaction reduces annual plant cover. California Agricul-
ture , September-October 1982, 6-7.