Study On Hydrological And Soil Erosion Control Effects Of Undergrowth Vegetation In Three Forest Stands In Simian Mountain Of Chongqing

In order to explore the quantitative relationship between undergrowth vegetations in different forest stands and water and sediment transport under the forest in the Three Gorges area of the Yangtze River,the hydrological and soil erosion control functions of different vegetations under the forest were studied,three common shrubs such as Sarcandra glabra Nakai,Maesa japonica Moritzi.ex Zoll and Orixa japonica Thunb were selected from the coniferous and broad-leaved mixed forests and the pure coniferous forests in Simian Mountain,Chongqing,and artificial rainfall was used to study the interception characteristics of single shrubs and litters under different rainfall intensities,and the interception characteristics of compound structure.The soil erosion control effeects of three kinds of artificial forests covered with litter on the slope were analyzed by the water discharge test.The research has certain significance for evaluating the function of different plantation under the forest ecological and hydrological cycle in the Three Gorges area,and it can play a guiding role in selecting a better understory vegetation allocation model.And can quantitatively study the hydrological and soil erosion control effects of litter layer under forest The test results are specifically as follows:(1)The interception of single shrubs,the interception of litter and the interception of shrubs and litter assemblages were all divided into three stages:rapid trapping phase,saturated and stable phase,and a post-rainfall drainage phase.(2)The maximum and minimum interception rates of three typical shrubs,Sarcandra glabra Nakai,Maesa japonica Moritzi.ex Zoll and Orixa japonica Thunb all show the first increase and then decrease with the increase of rainfall intensity.(3)There was a positive correlation between the maximum interception of litter and rainfall intensity.The unit area quality of the litter with interception of the litter also show a positive correlation.When the litter mass is small,the maximum water holding capacity of each shrub litter is less than the maximum and minimum interception under different rain intensity.When the litter mass increases to a certain amount,shrub litter will appear.The maximum water holding capacity is greater than the maximum and minimum interception when the rain intensity is 35mm/h,but both are less than the maximum and minimum interception at 70,95mm/h rain intensity.(4)Compared with single shrubs and litter alone test,the maximum interception of composite structure showed a positive correlation with rainfall intensity,and the rapid trapping phase took longer and the maximum interception was larger.And produce better interception Undergrowth shrubs and litters all play an important role in the process of water transport.Litters have a greater contribution to water interception.Therefore,rationally constructing and arranging the undergrowth vegetation can effectively retain water,which has a certain positive effect on reducing the soil erosion in forest land.(5)The rate of occurrence and the rate of sediment yield on the slope showed zero with the change of time,then increased rapidly to a certain value and then decreased slightly and maintained the fluctuation of the up and down within a certain range.Under the same unit area quality conditions,the order of the occurrence of runoff plots covering the litter was coniferous and broad-leaved mixed forest>coniferous forest>broad-leaved forest;the sediment yield time also appeared earlier in the broad-leaved forest.However,the order of maximum runoff rate and maximum sediment yield of covered litter runoff plots under three types of artificial forests were coniferous forest>coniferous and broad-leaved mixed forest>broad-leaved forest.(6)The litter cover can significantly reduce the runoff and sediment yield on the slope.Among the factors affecting the runoff and sediment yield on the slope,the discharge flushing intensity has a greater impact on the slope runoff and sediment yield.Under the three types of artificial forests The total amount of runoff covering the litter plot increased with the increase of rainfall intensity;and with the increase of rainfall intensity,the maximum sediment yield rate of the covered litter plot also increased.