Hunan Huitong Cunning Hamialanceolata Forest Canopy Interception Process Research

This study in Hunan in the Chinese fir plantation ecosystem Field Station II water testing areas in Hunan,in conjunction with the Chinese fir plantation as the research object,based on the extraction of canopy structure on the observed hydrological effect of the canopy interception,throughfall and stemflow,and to explore the factors in conjunction with the variation characteristics of Chinese fir plantation canopy rainfall redistribution effect,provide basic data and theoretical basis for the water balance in Chinese fir plantation and forest ecosystem hydrological function mechanism research.The main results are as follows:(1)The characteristics of atmospheric precipitation determine the form of forest water circulation,especially the rainfall intensity and rainfall magnitude,which affect the formation rate of forest runoff.The 2015 test were investigated in 105 rainfall,the measured precipitation was 1535.0mm,maximum rainfall is 122.1mm,the minimum rainfall is 0.2mm,the average rainfall is 14.6mm,the average rainfall intensity 1.6mm/h;rainfall mainly with light rain,moderate rain,heavy rain,heavy rain,heavy rain did not appear;total the rainfall duration is 959h,the long time rainfall is 56h;rainfall before the longest dry period is 269h,the average before the drying period is 71.3h.(2)In the relationship between forest and precipitation,the distribution of precipitation on the canopy layer of different vegetation is different.This paper studies that 2015 test stand outside the total precipitation is 1535.0mm,which produced 95 times,throughfall,throughfall amount was 1252.6mm,the average throughfall is 13.2mm;produce stemflow rainfall was 33,stemflow amount was 28.2mm,the average stem flow is generated from 105 0.85mm;canopy interception.The canopy interception amount was 254.2mm,the average canopy interception was 2.42mm.(3)Different rainfall intensity and rainfall magnitude have different effects on the rainfall redistribution in the canopy.With the increase of rainfall intensity,the average throughfall rainfall and average stemflow increased obviously,but the canopy interception rate was negatively correlated with rainfall intensity.Comparison on the dynamic process of rainfall in different rainfall magnitude,in the early stage of rainfall,the canopy interception and rainfall fitting is higher,but with rainfall increasing,canopy interception has a critical point;the increase slowed or negative.The rainfall is less than canopy interception of saturated water content under the condition of throughfall and stemflow may not occur;as the rainfall increases to canopy over saturated water,will produce stemflow;in rainfall for heavy rain,heavy rain or heavy rain,the canopy rapid saturation excess rainfall will exist the branches,and under the action of gravity,rainfall in throughfall and stemflow form fall,the equivalent of the canopy is a temporary storage,will be released after the temporary storage of rainfall,rain delay effect.(4)In Hunan in 2015 in conjunction with the Chinese fir plantation canopy interception was 254.2mm,the canopy interception rate was 16.55%,.The Gash model is used to simulate the annual cumulative canopy interception of 235.52mm,the simulation value is smaller than the measured value of 18.64mm,which is about 7.37%.(5)Study in Hunan in conjunction with the Chinese fir plantation throughfall,stemflow and canopy interception and precipitation outside the forest was positively related.It can be concluded from the fitting equation that the saturated water holding capacity of S is 1.327mm,the water holding capacity of S_t is 0.261mm,and the stemflow coefficient is P_t(0.029mm).The S value had the greatest impact on the model.When the S value increased by 10%,the simulated value of canopy interception increased by 8.42%.When the S value was reduced by 10%,the simulated value of canopy interception decreased by.(6)In Hunan in conjunction with the Chinese fir plantation canopy Gash model simulated results show that the model can adapt to the study area of canopy interception simulation well.In 2015,the simulated value of canopy interception of 105 rainfall was 235.5mm,the measured value was 254.2mm,and the simulated value(Im)was lower than the measured value(Is)of 18.64mm.In this paper,the sensitivity analysis of model parameters,the model is mainly affected by the E/R the value,because the average evaporation rate(E)and the average rainfall intensity R)are affected by seasonal climate variables,day and night,wind speed and other factors,choice of scale is small,the E/R is the value of high precision.