Study On The Hydrological Effects Of The Pinus Tabulaeformis Artificial Forests In Loess Plateau

Using the Loess Plateau Pinus tabulaeformis plantation as the research object, the hydrological effects of canopy, litter and soil are analyzed with the measured data of2008-2011, and the forest hydrological effects model for the region is established based on theoretical analysis and experimental data. The main results include:1. The relationship between throughfall, stemflow, canopy interception and rainfall could be described with the function y=a+b·x, which has good stability and meet the needs of the region; the relationship between throughfall rate, stemflow rate and rainfall could be described with the function y=a+b·x/(c+x), while the relationship between canopy interception rate and rainfall could be described with the function y=a+b/(c+x); by using partial correlation and stepwise regression and introducing other factors, the more detailed canopy interception model is established: I=a·P+b·M+c·V+dI—Interception, P—rainfall,M—Air relative humidity, V—Average water surface evaporation during rainfall.2. The relationship between litter interception and rainfall could be described with the function Ic=a·Pb. By using partial correlation and introducing rainfall duration and average water surface evaporation during rainfall., the more detailed canopy interception model is established: Ic=a·Pb+c·D+d·VIc—Litter interception, P—rainfall,D—Rainfall duration, V—Average water surface evaporation during rainfall.But the model improvement is not too notable, and in order to make the model as simple as possible, the model Ic=a·Pb is still an appropriate model.3. The relationship between soil moisture changes and other factors is: Wv—The difference between current soil weight and last soil weight, t—The time period, Wt—The last soil weight, V—Average water surface evaporation, P—Rainfall,the remainders are parameters.4.The relationship between forest hydrological effect and other factors is:We—The difference between soil moisture changes within weather station and soil moisture changes within forest for the period of time t, that is exactly We=(wout-Wout)-(win-Win),which wout and win denote the current soil weight within weather stations and the current soil weight within forests, Wout—The last soil weight within weather stations,Win—The last soil weight within forest, P—Rainfall, Pt—Temperature,Pm—Humidity,Pv—Wind velocity,Pc—Canopy density,Pl—Leaf area index,Ph—The thickness of the canopy, the remainders are parameters.