Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/2/2002
Publication Date: 1/1/2003
Citation: KEMP,P.R., REYNOLDS,J.F., VIRGINIA,R.A., WHITFORD,W.G. DECOMPOSITION OF LEAF AND ROOT LITTER OF CHIHUAHUAN DESERT SHRUBS: EFFECTS OF THREE YEARS OF SUMMER DROUGHT. JOURNAL OF ARID ENVIRONMENTS. 2003. V. 53(1). P. 21-39.
Interpretive Summary: One of the most important ecosystem processes in any ecosystem is decomposition and the relationship of this process to soil nutrient availability. In desert ecosystems where rainfall is unpredictable and extremely variable, it is important to understand the effects of long periods without rainfall on key ecosystem processes. This study was designed to examine the effect of summer drought by use of 'rain-out' shelters constructed over trenched-lined plots centered on individual creosotebushes (Larrea tridentata) and individual mesquite coppices (Prosopis glandulosa) on decomposition of senesced leaf foliage and on roots. Previous published studies have documented that leaf litter on the soil surface decomposes primarily by abiotic mechanisms, i.e., high temperatures and ultraviolet light, and that decomposition of roots and buried litter is biotic and regulated by soil moisture. The leaf litter decomposed faster than roots and independent of rainfall. Imposed drought significantly reduced the rate of decomposition of roots. The data from this study was used to test the effectiveness of a modified version of the CENTURY model (a simulation model initially developed for short-grass steppe). The modified model was able to predict most but not all of the observed decomposition rates. The most important conclusion from this study is that the key ecosystem process of decomposition is only weakly linked to precipitation patterns in arid rangelands.
Technical Abstract: One of the more uncertain aspects of nutrient cycling in desert ecosystems is the extent to which decomposition is controlled by water availability. Some of this uncertainty may be partly related to the duration of the studies and/or differences in the chemical composition of the decaying litter. We conducted a 3-year field study of rainfall to determine the impact of summer (June through September) drought on decomposition of leaf and root litter of two shrub species (Larrea tridentata and Prosopis glandulosa) in the northern Chihuahuan Desert, New Mexico, USA. In both species, leaf litter decayed at a faster rate and was less effected by drought than root litter. Drought had no influence on the rates of decomposition of leaves of either species during the first 18 months but caused decay rates to decline by about 25% during the latter half of the study. Drought decreased decay of root litter in both species by about 25% throughout the 3 years. There was a general increase in percent nitrogen (%N) of decomposing leaf litter in both species. Root litter %N declined slightly in Larrea but remained relatively constant in Prosopis. Using a modified version of the CENTURY model, we were able to predict most aspects of observed leaf and root litter mass loss and nitrogen dynamics. Overall, the results of this study suggest that relatively large changes in precipitation produce comparatively small changes in rates of decay of both leaf and root litter.