Study And Simulation Of Canopy Interception Characteristics Of Different Tree Species In Beijing Mountainous Area

In order to study the redistribution rule of canopy to rainfall,and try a new experimental method of canopy interception research to verify the applicability of Gash model in this area,this study took Robinia pseudoacacia,Platycladus orientalis and Pinus tabulaeformis forests as the research objects,analyzed the characteristics of canopy interception,throughfall and stemflow of three forest stands,and revealed the rainfall redistribution characteristics of the main dominant tree species in this area.Based on three tree species and by controlling the leaf area index,the simulated canopy for artificial rainfall experiment was developed and studied.The artificial rainfall experiments with different rainfall amount,different rainfall intensity and leaf area index with the same rainfall amount were carried out.The simulated results were compared with the measured values of sample plots(1)During the study period,the measured canopy interception of Robinia pseudoacacia,Platycladus orientalis and Pinus tabulaeformis accounted for 26,08%,29.79%and 34.34%of the rainfall outside the forest in the same period,respectively.The canopy interception capacity of the three tree species was in the middle and upper levels(10%-40%)of the canopy interception capacity of different stands.(2)Under the same rainfall condition,the throughfall and stemflow of simulated canopy will increase with the increase of rainfall intensity,and the interception of canopy will decrease with the increase of rainfall intensity outside the forest.The trend of the decrease of canopy interception will slow down with the increase of rainfall intensity.With the increase of LAI,the forest canopy throughfall and stem flow of the simulated canopy of the same tree species will gradually decrease,but the canopy interception will gradually inerease.The forest canopy throughfall and stem flow of the simulated forest canopy under different rainfall conditions and natural rainfall conditions will increase with the increase of rainfall outside the forest.Through fitting,it is found that both of them have a linear relationship with rainfall outside the forest.The rate of throughfall increases rapidly with the increase of rainfall outside the forest at first,then tends to be stable,and the canopy interception rate increases with the increase of rainfall outside the forest.The increase of rainfall decreases rapidly at first,and then becomes stable gradually.Both of thef are power exponential functions with rainfall.(3)Compared with the measured values under natural rainfall conditions,although there are gaps between the eigenvalues of simulated canopy and the measured values,the curves of the interception eigenvalues of simulated canopy and the rainfall outside the forest are consistent with the measured values under natural rainfall conditions.Under conditions of artificial rainfall,canopy interception test of canopy model with leaf area index as control variable can better reflect canopy intercePtion characteristics of tree species under natural rainfall conditions.This study can provide a new research and test method for canopy interception research.(4)The simulated canopy interception rates of Robiniapseudoacacia,Platycladus orientalis and Pinus tabulaeformis were 24.57%,28.20%and 32.32%respectively,which were lower than the measured values of 1.51%,1.59%and 2.02%,respectively.The simulated and measured values are basicaly matched.Sensitivity analysis of Gash model parameters foxund that during the study period in this area,the capacity for sustaining water(S)of canopy branches and leaves and average evaporation rate(?)of saturated canopy are the most important parameters affecting canopy interception.