Rainfall and decomposition in the chihuahuan desert.

We tested the hypotheses that rates of decomposition in a desert should be higher following single large rain events of 25 mm than evenly spaced 6 mm events and that supplemental rainfall should result in higher populations of soil biota. There were no significant differences in mass losses of creosotebush, Larrea tridentata, leaf litter on plots receiving water supplementation and no added water. On some sampling dates, there were higher mass losses in the 6 mm·week-1 treatment. Weekly rainfall produced higher coefficients of variation in mass losses than the other rainfall regimes. A single event pulse compared with weekly pulses of rainfall during the normal "dry" period resulted in no differences in mass losses. Microarthropods and nematodes exhibited numerical responses to supplemental rainfall but the litter microflora did not. These studies provide direct experimental evidence that the conventional wisdom linking decomposition to rainfall in deserts is wrong. The studies also suggest that the effects of litter fauna on surface litter decomposition are minimal; therefore, future studies should focus on activites of the microflora.