Comparisons of stemflow yield and efficiency between two xerophytic shrubs: the effects of leaves and implications in drought tolerance

Abstract

Abstract. Stemflow transports enriched precipitation to the rhizosphere and is highly important for the survival of xerophytic shrubs in water-stressed ecosystems. However, its ecological significance has generally been underestimated because it is relatively limited in amount, and the biotic mechanisms that affect it have not been thoroughly studied at the leaf scale. In this study, the branch stemflow volume (SFb), the shrub stemflow equivalent water depth (SFd), the stemflow percentage of incident precipitation (SF%), the stemflow productivity (SFP), the funnelling ratio (FR), the rainfall characteristics and the plant traits of branches and leaves of C. korshinskii and S. psammophila were measured during the 2014 and 2015 rainy seasons in the northern Loess Plateau of China. This study evaluated the stemflow production efficiency for the first time with the combined results of SFP and FR, and sought to determine the inter- and intra-specific differences in stemflow production and production efficiency, as well as the specific bio-/abiotic mechanisms that affected stemflow. The results indicated that precipitation amount was the most influential rainfall characteristic that affected stemflow in these two endemic shrub species and that stem biomass and leaf biomass were the most influential plant traits in C. korshinskii and S. psammophila, respectively. C. korshinskii had a greater stemflow production and production efficiency at all precipitation levels, and the largest inter-specific difference was generally in the 5‒10-mm young shoots during the most frequent rainfall events of ≤2 mm. C. korshinskii had a lower precipitation threshold (0.9 mm vs. 2.1 mm for S. psammophila), which provided more available water from rainfall for stemflow. The leaves affected stemflow production, and the beneficial leaf traits contributed to the higher stemflow production of C. korshinskii. In summary, C. korshinskii might have greater drought tolerance and a competitive edge in a dryland ecosystem because of greater and more efficient stemflow production, a lower precipitation threshold and more advantageous leaf traits.