Arid and semiarid lands occupy an increasingly large portion of the world's land surface. Decomposition processes in arid and semiarid environment have some unique characteristics due to the distinct physical environment, for example, low rainfall and relatively high solar radiation. In these ecosystems: (1) leaching is not an important decomposition process as opposed to temperate and tropical environments; (2) fragmentation and chemical alteration may be separated both temporally and spatially; (3) the ultimate location of plant litter is more important than its physical-chemical structure; (4) a variable quantity of the litter input in a desert ecosystem can be buried under the soil surface. The buried litter decomposes more rapidly than surface litter though it goes through the same pathway of chemical transformation as the surface litter; and (5) photodegradation may dominate aboveground litter decomposition. This process provides a shortcut in the carbon cycle, with a substantial fraction of vegetation carbon being lost directly to the atmosphere without cycling through the soil organic matter pools.
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