FACTORS AFFECTING LOSS IN MASS OF CREOSOTEBUSH LEAF-LITTER ON THE SOIL SURFACE IN THE NORTHERN CHIHUAHUAN DESERT

We examined the relative importance of biotic factors (microarthropods , termites, and fungi), and abiotic weathering on loss in mass of creo sotebush leaf-litter on the soil surface in the northern Chihuahuan De sert. We treated litter with either an insecticide (chlordane), a fung icide (benomyl), a general biocide (HgCl2-CuSO4 solution or, as a cont rol, distilled water. Our results suggest that microarthropods and fun gi do not play significant roles in creosotebush litter decomposition in arid habitats. The rate of loss in mass from fungicide treated litt er was not significantly different from control litter. Litter in fung icide treatment plots differed from that of the abiotic treatment plot s in having higher rates of loss, suggesting that other components of the litter communities compensate for the lack of certain organismal g roups. The rate of loss in litter treated with the general biocide dur ing late summer was not significantly different from the rates for oth er litter, demonstrating that abiotic factors have an important effect . We suggest that these factors include intense sunlight and high UV-r adiation and heat of the soil surface in summer. Actual evapotranspira tion and decomposition rates of surface litter are uncorrelated in des ert ecosystems. This may be due to abiotic fragmentation of the litter and the necessity of a threshold (amount or intensity) of rainfall wh ich is necessary to fragment litter and wash it into the soil.