Study On Natural Sparse Power Law Of Mountain Forest

The natural sparse power law is the mainstream direction of current research on population dynamics.This law reflects the dynamic changes of forest sparseness from the individual scale,revealing the statistical power law relationship between biomass and forest density.The measurement and analysis of biomass is an important part of the study of natural sparse power law,and it is also one of the hot spots in ecological statistics.In this paper,through field survey and sampling of Chongli Mountain in China,we obtain forest-related data and information,and build a non-linear mathematical model for the biomass of birch and larch in this area.On this basis,we apply the natural sparse law and density effect theory to explore the natural sparse power law of mountain forests.Then according to the fitting results,we analyze the statistical relationships among the average breast diameter,average wood cut area,average above-ground biomass and stand density.The statistical conclusion summarizes the intra-population competition in the forest ecosystem.The main conclusions are as follows:(1)In the birch and larch biomass models,there is a significant correlation between tree trunks,branches,and above-ground biomass and DBH(D)and tree height(H).The fitting formulas of birch and larch trunk biomass models are Wbirch=0.088D2.041H0.068 and Wlarch=0.003D2.392H0.202;then the branch biomass model fitting formulas are Wbirch=0.047D2.398H0.272 and Wlarch=0.003D2.409H-0.421;the aboveground biomass models are Wbirch=0.138D2.725H0.254 and Wlarch=0.003D2.392H0.202,respectively.(2)The non-linear mathematical model has a better fitting effect in the biomass fitting process of the two tree species,and the fitting effect is the best in the W=aDbHc model in which the DBH(D)and the tree height(H)are variables.And it shows that the biomass model obtained from the birch and larch sample data in the standard plot is highly accurate and the model design is reasonable.Each part of the biomass model is highly compatible with the above-ground total biomass model,but the disadvantage is that the birch forest is harvested.A large number of leaves are lost during the transportation,which causes the fitting effect of the leaf biomass model to be unsatisfactory.(3)In the study of natural sparseness,the power function equation better reflects the law,the fitting relationship between the average DBH of the forest stand and the stand density in this region is D=3.179?-0.748;the fitted relationship between the average wood area of the stand and the stand density is g=7.118?-1.547;the fitted relationship between the average above-ground biomass and stand density is W=17.909?-1.691.(4)According to the fitting results,it can be found that the average DBH,the average wood area,and the average above-ground biomass all decrease with the increase of stand density,and have a negative correlation.When the stand density is about 0.5 plants/m2,the population will reach a relatively stable state.In addition,in this study,the intra-species and inter-species competition of natural residual forests and artificial mixed forests are considered as self-sparse factors.The resulting natural sparse power index(?=-1.691)is slightly larger than that proposed by Yoda under the assumption of natural pure forests.Synthesizing this study,based on the tree height and DBH indicators in forestry surveys,a mathematical model of birch and larch biomass is well constructed,and the relationship between the individual tree size and the degree of sparse forest is further explored,which provides a reference for other similar research areas of forest biomass and offers a theoretical basis for the protection and restoration of natural forests defective forest ecosystems.