Changes of Rainfall Partitioning and Canopy Interception Modeling after Progressive Thinning in Two Shrub Plantations on the Chinese Loess Plateau

Abstract

Understanding the interaction between the hydrological cycle and vegetation management strategies, such as thinning, is essential to improve watershed management and support ecological services. However, it remains unclear how thinning affects the key components of hydrological cycle of dense shrublands in the semiarid regions. Thus, the purpose of this study was to analyze and evaluate the effect of thinning on rainfall partitioning and interception simulations in dense shrublands. In a 5-year field experiment, we compared rainfall partitioning in two re-vegetated shrublands (Caragana korshinskii and Salix psammophila) in the Chinese Loess Plateau under two thinning intensities (moderate thinning [MT] and heavy thinning [HT] refer to the removal of 25% and 50% of the branches, respectively) or no thinning (NT) (control). We modeled canopy interception losses (I) in the two thinning treatments and control treatment using the revised Gash model. The results showed that under MT and HT, the throughfall (TF) rate increased by about 12% and 20%, respectively, compared to NT. The stemflow (SF) and observed I rates decreased by about 26% and 33%, respectively, under MT, and the corresponding values for HT were about 50% and 52%, respectively. The observed I rate decreased proportional to the percentage of biomass removed from the C. korshinskii and S. psammophila plots. The results also revealed a significant linear correlation between the plant area index (PAI) value and the canopy water balance of the two shrub plantations (R2 > 0.83, P < 0.05). The performance of the revised Gash model (i.e., relative error [RE] < 20%) was satisfactory according to the Nash − Sutcliffe model efficiency (NSE) coefficient (0.34–0.71). Based on the RE values, the performance of the revised Gash model was better when applied to the plots subjected to MT and HT (RE ≤ 3%) than NT (RE = 9.3%) for S. psammophila. Changes in the canopy storage capacity and canopy evaporation rate strongly affected changes in simulated interception loss. The model can facilitate water management in semiarid shrub plantations by accurately simulating the effect of thinning on interception loss.