Interactions among soil biota in desert ecosystems

In desert systems, the availability of soil nitrogen can be the single most limiting factor controlling plant growth during periods of adequate soil moisture. Decomposition and nitrogen-mineralization rates prior to or during peak periods of plant growth can therefore be critical. Decomposition rates in deserts are generally high, and are relatively independent of rainfall. These high rates can be attributed to a combination of abiotic weathering, the types of microflora and microfauna associated with plant litter, and the adaptations of the soil biota to moisture pulses. The factors controlling litter decomposition and subsequent nitrogen mineralization are dependent upon the location of the organic matter in the habitat. The breakdown of surface litter occurs primarily through either abiotic weathering or by termite consumption. Microarthropods do not appear to have any role in the decomposition of surface litter owing to abiotic constraints on activity. The decomposition of roots, and buried litter, however, has been shown to be dependent on the presence of soil microarthropods. Microbial-microfaunal activity in the root region of desert plants may also have a significant effect on the short-term cycling of nitrogen in arid systems.