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United States Department of Agriculture

Agricultural Research Service


item Whitford, Walter

Submitted to: Biodiversity and Conservation Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/7/1994
Publication Date: N/A
Citation: N/A

Interpretive Summary: This paper examines the roles of various groups of soil animals in maintaining the soil processses that are necessary for plant growth. Termites are the single largest consumer of dead plant materials in temperate and tropical rangelands. Termites have a direct effect on soil organic matter content thereby affecting the spatial distribution of available soil nutrients. Some species of ants also affect the spatial distribution of soil nutrients. Other groups of soil animals that play important roles in rangelands are microscopic mites (related to ticks and spiders) and nematodes (very simple worms). Because soils in arid regions are dry most of the year, only those organisms that do not require free water in which to live can be active all of the time. Those organisms include some kinds of microscopice mites, termites and ants. Some kinds of soil fungi can continue activity in dry soils but most kinds of soil microorganisms exist in some drought resistant resting stage most of the time. Small mites that can move through the small pores in soil are most important grazers on fungi and these mites control the rates of mineral availability for plant growth. Limited data from other parts of the world suggest that the same kinds of animals live in soils of arid regions world-wide.

Technical Abstract: The importance of soil biota in maintaining ecosystem integrity is examined by a review of studies of soil processes and soil biota in arid ecosystems. In decomposition and mineralization processes, there is a temporal succession of microarthropod and nematode species. Tydeid mites are keystone species in the early stages of decomposition. Soil pore neck size evariation affects the spatial distribution of soil biota and 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 potential and soil temperature. The structure of soil microarthropod assemblages is similar in several arid regions of the world and abundance and diversity are directly related to quantity of litter accumulations and soil organic matter. The unique life histories and behavioural characteristics 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 essential resources (water and nutrients), are essential to the maintenance of the ecosystem integrity of arid ecosystems.

Last Modified: 10/19/2017
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