| In order to preferably analyze the forest hydrological processes and the mechanism of forest canopy hydrological function in loess plateau, this study based on the artificial Pinus tabulaeformis forest in study area as the research object, on the basis of the long-term monitoring of rainfall and throughfall, study and discuss the redistribution of rainfall and the spatial heterogeneity of throughfall. Main results are as follows:(1) During the study period (2011-2013), there are67times of rainfall were observed, among them, the moderate rain are the most, it takes50.75%of all rain; In the three factors of rainfall, the average rainfall intensity and the duration of rainfall, rainfall characteristics have the biggest variation coefficient,it is94.47%; In the different level of rainfall, the frequency of10.0～15.0mm is the highest, it is20.9%, and>50mm have the highest contribution rate to total rainfall, it is35.93%; In different rainfall intensity level, the frequency of1.0～2.0mm/h is the highest, it is23.88%,5.0-10.0mm/h have the highest contribution rate to total rainfall, it is27.36%;In different level of rainfall duration, the frequency of6-12is the highest, it is23.88%,12～24h have the highest contribution rate to total rainfall, it is44.24%.(2) The rainfall redistribution ratio of Pinus tabulaeformis as follows:throughfall84.91%, stemflow1.62%, interception of canopy13.47%; The rate of throughfall changes from71.17%to88.09%under the different rainfall levels, the relationship between throughfall and rainfall is positively correlated; The rate of stemflow changes from1.57%to2.07%under the different rainfall levels, the relationship between stemflow and rainfall is correlated, but does not significant under the level of0.05; The rate of interception of canopy changes from10.15%to26.95%under the different rainfall levels, the relationship between interception of canopy and rainfall is correlated, but does not significant under the level of0.05.(3) The effect forest canopy of rainfall input delay embodied in:throughfall begin time average delay34minutes, maximum delay time is181minutes; End time average delay1minute, the maximum delay time is104minutes; stemflow begin time average delay83minutes, maximum delay time is383minutes;End time average delay99minutes, the maximum delay time is320minutes;The average delay time of stemflow is2.44times of throughfall.(4) The phenomenon of begin time and end time delay is exist in four typical field rainfall, but there showed no obvious regularity on the delay time.Most of the areas of instantaneous rainfall less than reunite the instantaneous intensity of rainfall, rainfall intensity and rainfall intensity to reunite rainfalls is delayed in the rush hours, but there are a few areas rainfall instantaneous rainfall intensity is greater than the reunite of rainfall intensity.(5)Throughfall percentage is different at different position, canopy structure is the major cause of the differences; At the same time, the throughfall in few sample sites are larger than rainfall, the reason for this phenomenon is the evident rainfall concentration, which might be caused by the canopy; The throughfall of each observation point increase with the increase of the rainfall, the coefficient of variation decreases with the increase of rainfall, and it is decreases with the increase of the average rainfall intensity; The average variation coefficient of throughfall during the research is24.23%,it ranges from15%to40%under the small rainfall, with the increase of rainfall, the coefficient of variation ranges from5%to20%; The average throughfall percentage increases with the increase of distance between sample site and stem, but it is not the farther distance between sample site and stem, the bigger thoughfall percentage; Throughfall percentage is negatively correlated to canopy density and canopy thickness; The variation coefficient of thoughfall decreases with the increase of distance between sample site and stem, increases with the increase of canopy thickness and canopy density; The influence of canopy density is the biggest (contribution rate51.07%), the second is distance between sample site and stem (contribution rate33.29%), the last is canopy thickness (contribution rate15.63%). |
PDF Full Text Request