Seasonal and Spatial Variation in the Soil Microarthropod Fauna of the White Sands National Monument

Abstract

The only microarthropod taxon found at all sample stations in a gypsum sand dune field was the mite Speleorchestes sp., family Nanorchestidae. The highest densities and largest number of taxa of microarthropods (Acari and Collembala) were under shrubs at the edge of the dune field. Changes in number of taxa and density were directly correlated with temperature and rainfall. During the warmer months, the microarthropod fauna was dominated by tydeid and tarsonemid mites under shrubs on dunes, and pyemotid mites in interdune spaces. The densities, number of taxa and taxonomic composition of the gypsum dune microarthropod fauna were similar to those found in non-gyphic soils on a nearby desert watershed. The few studies of desert soil faunas have been conducted in areas of stable soils (Wallwork, 1972; Santos et al., 1978; Franco et al., 1979). These studies indicated that prostigmatid mites dominate the soil fauna of North American hot deserts. Further, these authors documented the relationship between plant litter accumulations or organic matter content and the density and diversity of the soil microarthropod fauna. The White Sands National Monument provides a unique ecosystem for examining the relationships of substratum stability and organic matter and the soil arthropod biota. In addition, the dunes and the soil are either pure gypsum or gypsum impregnated, thus providing an opportunity to examine the effect of this limited habitat type on the soil microarthropod fauna. Because of the instability of the dunes and the chemical composition of the White Sands, we hypothesized that the density and taxonomic diversity of