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 creosotebush leaf-litter on the soil surface in the northern Chihuahuan Desert. We treated litter with either an insecticide (chlordane), a fungicide (benomyl), a general biocide ($\text{HgCl}_{2}\text{-CuSO}_{4}$ solution or, as a control, distilled water. Our results suggest that microarthropods and fungi do not play significant roles in creosotebush litter decomposition in arid habitats. The rate of loss in mass from fungicide treated litter was not significantly different from control litter. Litter in fungicide treatment plots differed from that of the abiotic treatment plots in having higher rates of loss, suggesting that other components of the litter communities compensate for the lack of certain organismal groups. The rate of loss in litter treated with the general biocide during late summer was not significantly different from the rates for other litter, demonstrating that abiotic factors have an important effect. We suggest that these factors include intense sunlight and high UV-radiation and heat of the soil surface in summer. Actual evapotranspiration and decomposition rates of surface litter are uncorrelated in desert ecosystems. This may be due to abiotic fragmentation of the litter and the necessity of a threshold (amount or intensity) of rainfall which is necessary to fragment litter and wash it into the soil.