Stemflow of a xerophytic shrub (Salix psammophila) in northern China: Implication for beneficial branch architecture to produce stemflow

Stemflow is an important mechanism to replenish soil water for xerophytic shrubs in water-stressed ecosystems, whereas the biotic influences of leaf and branch on shrub stemflow were not completely investigated. In this study, the stemflow of 98 branches with various basal diameter under 42 rainfall events was measured for Salix psammophila in northern China during the rainy seasons of 2014 and 2015. The effects of rainfall characteristics, and plant traits of leaf and branch on stemflow were detected. Stemflow productivity (branch stemflow production of unit biomass) was proposed to determine the beneficial branch architecture for efficient stemflow production. The developed allometric equations by expressing the plant traits as a power function of branch basal diameter could satisfactorily estimate the leaf traits and biomass. There were significant differences of branch stemflow between different basal diameter and precipitation classes. The average shrub stemflow depth and percentage was 0.77mm (0.004–3.32mm) and 5.54% (0.70–7.92%), respectively. The precipitation amount and leaf fresh biomass were identified as the most influential rainfall characteristic and plant trait of stemflow, respectively. The stemflow production increased linearly with precipitation amount, and stemflow percentage increased with precipitation amount to approach the asymptotic value of 7.61%. The threshold precipitation amount of 2.1mm was required to initiate shrub stemflow. The stemflow productivity decreased with basal diameter of branches and increased with precipitation amount. Allocating aboveground biomass to grow new branches and develop small ones was an energy-conserving strategy to ensure stemflow production. The branch architecture with more small branches, higher leaf biomass, and larger branch angle was more efficient for stemflow production.