Research On Structure And Function Of Water Conservation Forests In Jinyun Mountain Of Chongqing City

The research on structure and function of water conservation forests of Jinyun mountain in Chongqing city was conducted,which are associated with the national 1 lth five-year key project of state forestry administration "Technology Research and Demonstration of Vegetation Construction with Water Conservation Function in Water district of northern Chongqing city"(2006BAD03A1802).The purpose of this paper is to provide evidence for vegetation construction with hydrological function in Chongqing city.Based on analysis of forest communities of Jinyun mountain,the slope runoff plots of 5 typical forest communities(Pinus massoniana and Gordonia Svchuanensvs mixed forest,Gordonia Svchuanensvs mixed forest,Phyllostachys pubescens forest,and shrub forest)and arable land (control),and standard plots of 4 typical forest communities(Pinus massoniana and Lindera kwangtungensis mixed forest,Lindera kwangtungensis and Cunninghamia lanceolata mixed forest, Phyllostachys pubescens mixed forest and Pinus massoniana burned area) in Jinyun mountain,northern Chongqing were selected research object in this paper.Mechanism and evaluation of water conservation, screening of the hydroglogical optimized structural model was conducted.Hydrological function mechanism of 9 typical forest communities was investigated based on the quantitative analysis in hydrological effects of canopy,understory vegetation,litters and soil horizon. Results showed that water-holding capacity of canopy in Pinus massoniana and Lindera kwangtungensis mixed forest is best(28.70t/hm~2 ),the capacity in Pinus massoniana burned area is worst(5.89 t/hm~2);water-holding capacity of understory vegetation in shrub forest is much higher than others(25.4t/hm~2);The best hydrolgogical function of litters is mainly observed within the first hour of precipitaiton,especially in the first 10 minutes,the maximum water retention in shrub forest which have good improvement on litters is much higher than others(15.61t/hm~2 );the amount of water-holding ability of soil horizon in different forest ranges from 363.1 to 432.1mm,the highest one is Pinus massoniana and Lindera kwangtungensis mixed forest.Then,the method of Analytic Hierarchy Process(AHP) was applied to establish the hydrological hierarchy function model of forest communities,and integrative grades were used to give static evaluation,the results of evaluation showed that:Pinus massoniana and Lindera kwangtungensis mixed forest(0.792)> Lindera kwangtungensis and Cunninghamia lanceolata mixed forest(0.786)> Phyllostachys pubescens mixed forest(0.775)> Pinus massoniana and Gordonia Svchuanensvs mixed forest(0.644)> Gordonia Svchuanensvs mixed forest(0.616)> shrub forest(0.604)> Pinus massoniana burned area(0.480)> Phyllostachys pubescens forest(0.491)> arable land(0.424),so Pinus massoniana and Lindera kwangtungensis mixed forest has optimal hydrological function.Dynamic evaluation based on observed runoff process of slope surface runoff,under ground runoff and throughfall of 5 slope runoff plots in different rainfall conditions showed that:canopy interception capacity of Pinus massoniana and Gordonia Svchuanensvs mixed forest is best in rainfall(<50mm),the rate is slightly better than Gordonia Svchuanensvs mixed forest in rainfall(<5mm,>10mm),the rate of Phyllostachys pubescens forest is better than Gordonia Svchuanensvs mixed forest in rainfall(5-10mm), better than them in rainfall(>50mm);the rate of shrub forest main keep over 40%and its capacity is obviously better than others.The function of cutting rainfall peak and flood and water control of Gordonia Svchuanensvs mixed forest is best in rainfall(<5mm,>25mm),the function of Pinus massoniana and Gordonia Svchuanensvs mixed forest is best in rainfall(5-10mm),the function of shrub forest is best in rainfall(10-25mm),so Gordonia Svchuanensvs mixed forest has optimal hydrological function.Based on RS&GIS technique,using remotely imagery and GIS datdabase to analyze the forest landscape spatial pattern in Jinyun Mountain,Chongqing.Spatial heterogeneity Landscape features, environmental factors and the distribution of hydrological function were explored and expained in the study area.With the help of six indices such as landscape patterns ratio,mean patch area,edge density,patch density,landscape diversity index,Shannon's evenness index and dominance were put forward to anal yze the patterns of forest landscapes in Jinyun mountain.Results showed that landscape fragmentation degree of water conservation forest is high,the edge and patch density are big in the whole level,the density of different area showed its heterogeneity.By putting map of DEM and vegetat ions together,the relationships between vegetation distribu tion and elevation,slope and aspectw as analyzed.The result show s:Several forest communities distri butes widely at the altitude during 425-575m,every vegetation class mostly distributes at the slope during 16°-45°,the area percent changes with normal distribution,the area of each vegetation type is above 30%at north westaspect.The maximum hydrology of Jinyun mountain is 3982263m3,the ratios of different vegetation as follows:Pinus massoniana mixed forest 66.48%,Gordonia Svchuanensvs mixed forest 14.61%, Neosinocalamus affinis mixed forest 6.34%,Phyllostachys pubescens mixed forest5.8%,Cunninghamia lanceolata mixed forest 5.5%,Symplocos setchuensis mixed forest 0.98%,Phyllostachys aurita mixed forest 0.28%.