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The dual role of soil crusts in desertification
Author(s) -
Assouline S.,
Thompson S. E.,
Chen L.,
Svoray T.,
Sela S.,
Katul G. G.
Publication year - 2015
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1002/2015jg003185
Subject(s) - desertification , vegetation (pathology) , surface runoff , environmental science , soil crust , arid , biological soil crust , plant cover , context (archaeology) , vegetation cover , hydrology (agriculture) , soil water , limiting , infiltration (hvac) , soil science , ecology , geology , geography , species richness , grazing , biology , geotechnical engineering , medicine , mechanical engineering , paleontology , pathology , meteorology , engineering
Vegetation cover in dry regions is a key variable in determining desertification. Soils exposed to rainfall by desertification can form physical crusts that reduce infiltration, exacerbating water stress on the remaining vegetation. Paradoxically, field studies show that crust removal is associated with plant mortality in desert systems, while artificial biological crusts can improve plant regeneration. Here it is shown how physical crusts can act as either drivers of or buffers against desertification depending on their environmental context. The behavior of crusts is first explored using a simplified theory for water movement on a uniform, partly vegetated slope subject to stationary hydrologic conditions. Numerical model runs supplemented with field data from a semiarid Long‐Term Ecological Research site are then applied to represent more realistic environmental conditions. When vegetation cover is significant, crusts can drive desertification, but this process is potentially self‐limiting. For low vegetation cover, crusts mitigate against desertification by providing water subsidy to plant communities through a runoff‐runon mechanism.