Rainfall redistribution and its spatial variation in the stand of Pinus armandii in the Liupan Mountains, China

During the growing-season (Jun.-Sep.) of 2004 and 2005, the throughfall, stemflow and canopy interception of a natural forest stand of Pinus armandii in Liupan Mountains Nature Reserve of northwestern China were observed. The rainfall distribution, the spatial variability of throughfall and their influencing factors were systematically analyzed. The result indicated that the throughfall, stemflow and canopy interception accounts for 84.34%, 0.72% and 14.94% of the rainfall in open field, respectively. The spatial variability of throughfall within this stand was estimated for different rainfall events. The coefficient of variance of throughfall decreases with increasing rainfall depth. It was found that the canopy has a congregation effect on the throughfall in a certain extend, and this effect increases evidently with increasing rainfall depth. The canopy structure characteristics, such as leaf area index (LAI), canopy density, canopy thickness, and the distance of sampling sites to the stem of sample tree, are very important factors influencing the spatial distribution of throughfall. Of these factors, the influence of LAI is the highest one. It was concluded that the canopy structure is one of the most important ecological factors that affect the rainfall redistribution and spatial variability within forest stand.