Stemflow, throughfall and channelization of stemflow by roots in three Chihuahuan desert shrubs

Three studies were conducted to examine precipitation-vegetation relationships in the multi-stemmed shrubs Larrea tridentata, Prosopis glandulosa and Flourensia cernua in a desert ecosystem. We measured stemflow and throughfall as affected by bulk precipitation, canopy architecture and stem-angles. Using fluorescent dye, we traced root channelization of stemflow water. Stepwise regression analysis showed that the best 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 accounted 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. Stemflow amounts collected during winter months do not differ significantly from those of summer months demonstrating that in these winter deciduous species the absence of leaves during winter months does not affect generation of stemflow. Analysis of variance showed that the percentage of throughfall was different among species suggesting that variations in canopy characteristics could explain, in part, these interspecific throughfall differences. Both stem-angle and stem-length had a significant effect on stemflow generation in F. cernua and L. tridentata, whereas there was only a significant relationship between stem-angle and stemflow in P. glandulosa. Analysis of rhodamine-B dye distribution under shrubs indicated that root channels are preferential pathways for movement of stemflow water into soil, and that this water is potentially the source of soil moisture which allows shrubs to remain physiologically active under drought conditions. (C) 1996 Academic Press Limited