The Responses Of Main Forest Types To Different Levels Of Disturbance In Yanqing County Of Beijing

The purpose of this study was to investigate the responses to different levels of disturbance in mountainous forest ecosystems at warm temperate zone.Typical plots investigation was applied in this study,using Songshan Nature Reserve,Zhenzhuquan forestry station and Sihai forestry station in Yanqing County of Beijing as study areas.Main forest types were investigated,including Pinus tabulaeformis forests,Quercus mongolica forests,Populus davidiana forests and broadleaved mixed forests.Sample plots of 20m~*30m were set up for measuring every live stumpage of plant species. Investigation on each species included height,canopy diameter,active clear bole height,dead clear bole height,growth classes,health status et al.At the same time,temporary quadrat of shrub and herb were sited in each sample plot,recording the boidiversity of shrub and herb and natural regeneration.Various index of sample plots was evaluated as well to record the degree of closeness and disturbance factor in forest.Principal component analysis on SPSS 15.0 was conducted for cluster analysis,selecting arbor,shrub, herb and land site and other main indices.Depending upon the outcome of the cluster analysis,the sample plots were grouped and verificatying to the remarkable classification of disturbance levels which were determined in the field.Due to the comparison,the patterns of biodiversity,natural regeneration and soil nutrient with respect to 4 representative communities were obtained at different levels of disturbance.The results were showed as below:1 From the perspective of biodiversity,diversity of arbor always declines in Pinus tabulaeformis forests,Quercus mongolica forests and Populus davidiana forests with the increasing degree of the community disturbance.Consistent conclusion is drawn from comparison:diversity of shrub and herb increases in moderate interference circumstances,then declines when the interference is getting worse. Because of influence of competition between communities,diversity of arbor ascends when the degree of disturbance is inclining in the broadleaved mixed forest.Meanwhile,diversity of shrub always rises. Diversity of herb is as the same as the pure forest.As for horizontal comparison,diversity of Pinus tabulaeformis forests is the lowest,whereas Populus davidiana forest and broadleaved mixed forest's are the highest.2 From analysis of regeneration in community,Quercus mongolica forests and Populus davidiana forests are vigorous.There isn't the successional trend of replaced after disturbance.Broadleaved mixed forests will be replaced by pure forests of climax community in succession.However,the view of which Pinus tabulaeformis forests will be replaced by pure forest of climax community in succession cannot be easy predicted,even the small number of regeneration.If tourism is mastered,Pinus tabulaeformis forests will have the ability of to be climax community with Broadleaved forests.The carrying capability of environment is the restrictive factor of community succession to balance point steadily.3 The concentration of organic matter in lightly degraded soil is of "inverted pyramid" decreasing trend with the increase of soil depth.The concentration of organic matter in soil of moderate and severe degradation increases when soil depth increases,but also shows a decreasing trend on the whole. However,a peak is observed when it's decreasing,which is deeper when the extent of degradation deepens.Organic matter in soil is the least affected from damage in Pinus tabulaeformis forests because of trait about difficult to resolute of forest litters in coniferous Forest.The concentration of organic matter is the highest in Populus davidiana forest,and affected is the most obviously.