A shrubland, a woodland, and two grassland habitats were compared for populations of soil microarthropods in a semiarid watershed of New Mexico. Densities of grass rhizosphere microarthropods were generally higher, and some taxa like sminthurid collembolans were essentially limited to the grama grassland habitat. However, the rhizosphere fauna was also not quantitatively or qualitatively different from fauna of unvegetated soil or soil below the litter layer except in the grama grassland habitat. The similarity in microarthropod faunas in the soils of the four major habitats shows soil microarthropod assemblages are more a function of the organic matter content of the soil and the microclimate of the upper 10 cm than of the individual plant species.