Spatial distribution and drivers of throughfall beneath shrub canopies in a semi‐arid desert steppe

Abstract

The spatial distribution of water is mainly controlled by the vegetation canopy, which determines the partitioning of rainfall into interception, throughfall (TF) and stemflow. TF is known to be a critical component of hydrological and biogeochemical cycles. Spatiotemporal patterns of TF have been studied in different ecosystems, although the majority of studies focused on forests. Few reports on small‐scale TF variability and drivers in semi‐arid desert steppes have been published. Herein, we investigated the variability of TF of two morphologically distinct artificial revegetation shrubs (Caragana liouana and Salix psammophila) within a semi‐arid desert steppe, synthesized the data and analysed the characteristics of TF distribution and drivers at the rainfall event scales. We found that (1) morphological differences were sufficient to generate significant (p < 0.05) differences in TF between the two shrub species under the same rainfall and meteorological conditions, with a TF percentage of 70.22% for C. liouana and 79.87% for S. psammophila; (2) a linear outward radical increase in TF was identified with increasing distance from the base of the isolated shrubs. Wind speed had a greater effect on the distribution of TF beneath the shrub structure for C. liouana, whereas the distribution of TF beneath the shrub structure for S. psammophila was more affected by wind direction; and (3) canopy architecture, in particular the stem angle and canopy base area, which affected the openness of the canopy and played an important role in the distribution of TF in the two shrubs. The results reveal the key factors driving water use under rainfall during revegetation and the TF utilization mechanism in semi‐arid areas and highlight the complementary effect of different species on ecosystem hydrological functions.