Stemflow Of Two Dominant Shrubs In Loess Plateau And Its Ecohydrologic Significance

Shrubs existing in semi-arid ecosystem will obviously changes the eco-hydrological processes. Shrubs partition rainfall into stemflow, resulting in a spatial distribution of nutrient of nutrient and water fluxes reaching the soil centered on the trunks of shrubs. In this study, stemflow of two main xerophytic shrubs, Caragana korshinskii and Hippophae rhamnoides was selected in Loess Plateau. The influence of meteorological condition on stemflow generation, interspecific and intraspecific variation in stemflow hydrology and the fate of stemflow water in the soil were measured. The main results are as follow:1. Caragana korshinskii, the amount of through (TF) was124.7mm (59.7%), of stemflow (SF) was25.7mm (12.3%), and of interception (IC was58.5mm (28%); Hippophae rhamnoides, the amount of through (TF) was153.1mm (73.3%), of stemflow (SF) was17.6mm (8.4%), and of interception (IC was38.2mm (18.3%). Regression analysis showed a significant positive liner correlation between rainfall and TF, SF, and I. Between rainfall, maximum intensity in10minutes (I10) and TF%, SF%, IC%of the two species showed the exponent or power function.2. The regression analysis was mainly impacted by the measurement approaches of the throughfall and leaf area index (LAI), with the maximum water storage capacity of0.68mm and0.72mm for Caragana korshinskii and Hippophae rhamnoides, respectively. The direct measurement was mainly impacted by the canopy structure; the maximum water storage capacity was estimated0.73mm and0.76mm for Caragana korshinskii and Hippophae rhamnoides, respectively. The direct measurement showed that the maximum water storage capacity per unit area of the canopy components was in the order of branches (0.31mm)> leaves (0.27mm)> trunks (0.15mm) for Caragana korshinskii, trunks (0.33mm)> branches (0.29mm)> leaves (0.14mm) for Hippophae rhamnoides.3. The average funneling ratios were156.6±57.1and49.5±30.8for C. korshinskii and H. rhamnoides, respectively. For individual rainfall event the wetting front depths in the root zone around the trunk of the shrubs were deeper than that in the bare area outside canopy and area beneath canopy. Correspondingly, soil water content was also higher in the root area around the shrub trunk than that in the area outside the shrub canopy.4. Analysis of dyeing tracing and soil moisture distribution under shrubs indicated that root channels were preferential pathways for movement of stemflow water into soil, and that this water was potentially source of soil moisture which allows shrubs to persist and even prosper under drought conditions.