RAINFALL INTERCEPTION BY MESQUITE ON THE ROLLING PLAINS OF TEXAS (PROSOPIS GLANDULOSA, STEMFLOW)

A three-year study was designed to determine the amount of rainfall that was intercepted by mesquite trees and absorbed or evaporated into the atmosphere. Measurements were made of the amount of rainfall that penetrated the mesquite canopy as throughfall, and was intercepted by mesquite trees and subsequently channeled as stemflow to the soil immediately surrounding the tree.; Honey mesquite (Prosopis glandulosa) harvested small (4.8%) amounts of rainfall and concentrated it at the base of the trees as stemflow. The stemflow was consistent for all rainfalls greater than 3 mm, but varied depending on the density of the individual tree canopy.; Regression equations accounted for 68 to 86% of the variability in predicting quantity of stemflow. A combination of storm characteristics and tree morphology characteristics that were difficult to characterize numerically appeared to influence the amount of stemflow, also.; Throughfall reaching the soil under the mesquite trees was relatively higher (91.1%) and interception loss much lower (4.1%) compared to most deciduous forests. The higher throughfall and lower interception loss is consistent with the open canopy and small leaves of these trees. The small leaf area is illustrated by a leaf area index of 0.532 for three small mesquite trees. The conclusion that mesquite leaves have little effect on throughfall was borne out by the insignificant (P > .05) difference in throughfall for trees with and without leaves.; Seventy-five percent of the mean annual rainfall (47.8 cm) at Post, Texas, falls May through October and would produce an estimated 103 liters of stemflow for three small trees. Based on reported evapotranspiration rates, the stemflow from these trees amounted to 35 to 40% of their yearly transpiration loss.; Substantial stemflow, high throughfall, and low interception loss maximize the amount of precipitation available to Prosopis glandulosa. Additional factors such as a shallow lateral root system, a deep tap root, and low transpiration rates when soil water potential is low, combine to provide drought avoidance for mesquite.