STEMFLOW, THROUGHFALL AND CHANNELIZATION OF STEMFLOW BY ROOTS IN 3 CHIHUAHUAN DESERT SHRUBS

Three studies were conducted to examine precipitation-vegetation relat ionships in the multi-stemmed shrubs Larrea tridentata, Prosopis gland ulosa and Flourensia cernua in a desert ecosystem. We measured stemflo w and throughfall as affected by bulk precipitation, canopy architectu re and stem-angles. Using fluorescent dye, we traced root channelizati on of stemflow water. Stepwise regression analysis showed that the bes t one-variable model for stemflow in L. tridentata was canopy volume, which accounted for 87% of variation. The best one-variable model for stemflow in P. glandulosa and F. cernua was canopy area, which account ed for 82% of variation in both species. Stemflow data from winter and summer months were statistically compared to determine the influence of leaves on stemflow generation in P. glandulosa and F. cernua. Stemf low amounts collected during winter months do not differ significantly from those of summer months demonstrating that in these winter decidu ous species the absence of leaves during winter months does not affect generation of stemflow. Analysis of variance showed that the percenta ge of throughfall was different among species suggesting that variatio ns in canopy characteristics could explain, in part, these interspecif ic throughfall differences. Both stem-angle and stem-length had a sign ificant effect on stemflow generation in F. cernua and L. tridentata, whereas there was only a significant relationship between stem-angle a nd stemflow in P. glandulosa. Analysis of rhodamine-B dye distribution under shrubs indicated that root channels are preferential pathways f or movement of stemflow water into soil, and that this water is potent ially the source of soil moisture which allows shrubs to remain physio logically active under drought conditions. (C) 1996 Academic Press Lim ited