Surface-active arthropods in a desert landscape: Influences of microclimate, vegetation, and soil texture on assemblage structure

CRAWFORD, C. s., 1988. Surface-active arthropods in a desert landscape: Influence of microclimate, vegetation and soil texture on assemblage structure. Pedobiologia 32, 373-385. The structure of surface-active arthropod assemblages in four different desert grassland habitats was studied for 1 yr at the Sevilleta National Wildlife Refuge, New Mexico. Overnight pitfall trap data, taken monthly, were examined to determine why detritivores are especially common in dune-associated habitats of deserts. A shrub-dominated site (the “Interdune’, habitat) was compared, therefore, with nearby (=1 km) “Mesquite”, “Creosote”, and “Grass” habitats. All habitats had similar proportional plant cover and climatic characteristics, but Interdune soils had more sand and less silt, clay, and organic matter. Interdune traps caught arthropods ≈ twice as frequently as other traps. Detrivore species dominated the Interdune fauna, while carnivore and ant species were more abundant in the other habitats. Richness and overall species diversity of nonsocial species were greatest in the Interdune, which shared reiatively few species with the other habitats. Termite activity (consumption of paper plates covering traps) was lowest in the Interdune. Neither habitat-specific vegetation features nor regional precipitation appeared to influence assemblage structure; however, soil temperatures usually correlated significantly with richness or diversity in all habitats. Only in the Interdune did the activity of nonsocial species increase with rising seasonal temperatures; soil temperature correlations with activity and/or diversity in all habitats may have masked more fundamental population changes. Physical conditions as well as detritus dispersal in sandy substrates may best explain the comparative intensity of activity among detritivores in dune-associated habitats.