The Role of Mites and Nematodes in Early Stages of Buried Litter Decomposition in a Desert

Abstract

We studied changes in populations of mites, nematodes, bacteria, and fungi in buried creosote bush litter treated with selected inhibitors. Elimination of microarthropods (primarily tydeid mites) resulted in increased numbers of bacteriophagic nematodes and reduction in numbers of bac- teria; elimination of both nematodes and microarthropods resulted in increased numbers of bacteria compared to untreated controls. Fungal grazing mites, Pyemotidae, and fungivorous nematodes, Aphelenchus sp., increased in numbers between days 25 and 30, reducing the fungi on untreated leaves but not on stems and petioles, while mean length of fungal hyphae increased in insecticide- treated leaves. Elimination of mites resulted in a 40% reduction in decomposition suggesting that in a desert, tydeid mites affect decomposition of buried litter by regulating the population size of the bacterial grazers, cephalobid nematodes. In our previous study (Santos and Whitford 1981), we found that tydeid mites were the initial arthropod colonizers of buried creosote bush litter and that or- ganic matter loss was significantly reduced in the ab- sence of these mites. We hypothesized that the tydeid mites were predators on free-living nematodes, and regulated decomposition by regulating the population size of microbial grazers (the nematodes).