Measurements and modeling of canopy interception in the Gongga Mountain subalpine succession forest

Gross rainfall,throughfall and stemflow were measured during the growing seasons of two tree species of Abies afbri and Populus purdomii in 2008 and 2009 in a subalpine succession forest on the Gongga Mountain. Throughfall (the net precipitation under the two tree species),steamflow and canopy interception are analyzed.In addition,the applicability of the Gash model (1995)is examined using the measurement.The model requires only a limited amount input and uses the Penman-Monteith equation for evapotranspiration estimation.The capacity of the canopy storage is calculated using the Preira method in the model.The results show that the throughfall can account for 76.4% and 77.0% of gross rainfall in 2008 and 2009,respectively,while the stemflow is too small to contribute the gross rainfall,and the remaining is intercepted by canopies.The amount of gross rainfall is found to be the main influential factor on the interception process compared to the rainfall duration and intensity.Simulations of canopy interceptions agree well with the observed values for the two growing seasons.For example,the values of simulated and observed interceptions are respectively 125.6 mm and 126.1 mm for the growing season of 2008,which illustrates that the applicability of the Gash model in this region.