THE IMPORTANCE OF THE BIODIVERSITY OF SOIL BIOTA IN ARID ECOSYSTEMS

The importance of soil biota in maintaining ecosytem integrity is exam ined by a review of studies of soil processes and soil biota in arid e cosystems. In decomposition and mineralization processes, there is a t emporal succession of microarthropod and nematode species. Tydeid mite s are keystone species in the early stages of decomposition. Soil pore neck size variation affects the spatial distribution of soil biota an d requires that species differ in size to provide efficient processing of organic matter. In arid ecosystems, the sub-set of soil biota that is active at any point in time is determined by the soil water potent ial and soil temperature. The structure of soil microarthropod assembl ages is similar in several arid regions of the world and abundance and diversity are directly related to quantity of litter accumulations an d soil organic matter. The unique life histories and behavioural chara cteristics of desert soil macrofauna (termites and ants) determine the effects of these organisms on soil properties and soil formation. The soil biota, by affecting the spatial and temporal distribution of ess ential resources (water and nutrients), are essential to the maintenan ce of the ecosystem integrity of arid ecosystems.