Study On Cutting Tree Determining Method Based On Forest Stand Spatial Structure Optimization

Stand spatial structure decides the competitive advantage and spatial niche betweentrees,and it affects growing,development and stability of the stand in a large extent.Logicalstand spatial structure is the basis of fully playing a variety of functions,studying stand spatialstructure means a lot to forest management and optimal decision both in theory andpractice.This paper takes4Larch coniferous and broadleaved mixed forest plots of differentcutting intensities which are located in Jingou forestry farm Wangqing forestry bureau Jilinprovince，one representative of over-logged forest areas in Northeastern China.The purpose ofthis study is to seek a new method for forest spatial structure analyzation and optimization，Voronoi diagram is selected to determine neighbor trees of the object one，mingling anduniform angle index are calculated based on the neighbor trees，and the results of mingling anduniform angle index calculated based on Voronoi diagram are compared with the resultscalculated based on4neighbor trees.Growth space of each tree is divided based on Voronoidiagram,weighted Voronoi diagram is introduced to divide the nutrient area.Competition isanalyzed based on nutrient area.Mingling and uniform angle index computed based on Voronoi diagram calculated withthe spatial structure program which programmed in Microsoft Visual Basic. Mingling of plotsof not cutting basal area,cutting basal area30%,cutting basal area20%and cutting basal area40%calculated based on Voronoi diagram are close to mingling calculated based on4nearestneighbor trees. Uniform angle index of the4plots calculated based on Voronoi diagram arevery different with uniform angle index which are calculated based on4nearest neighbor trees.The uniform angle index which calculated based on4nearest neighbor trees showed trees ofnot cutting plot are aggregated distribution,trees of plots of cutting basal area30%,cuttingbasal area20%and cutting basal area40%are random distribution.Uniform angle index of the4plots calculated based on Voronoi diagram shows the the4plots are aggregated distribution.Average nutrient area and competition pressure index of not cutting plot are5.0m2and120 which are calculated based on weighted Voronoi diagram and tree crown area.Nutrient area ofplots cutting basal area30%，cutting basal area20%and cutting basal area40%are large than309’s and competition pressure index all are106.Competition intensity of cutting basal area30%plot，cutting basal area20%plot and cutting basal area40%plot is lower than not cuttingplot.32trees are cutted according to the analysis of the plot and the quantity is less than themaximum.Species composition index of not cutting plot decreased from0.6309to0.6and theq value is1.65，mingling and nutrient area and copetition pressure index improved comparedwith before adjusted. Uniform angle index is0.6358which calculated based on Voronoidiagram，but reduced which calculated based on4nearest neighbor trees. The study shows thatthe number of neighbor trees determined according to Voronoi diagram and4nearest neighbortrees is different，the frequency of5and6neighbor trees is the highest，and the averageneighbor trees is6of the4plots，accordingly，the standard angle should be adjusted accordingto the number of neighbor trees.Thinning properly can improve the spatial structure in short time，wheras naturalsuccesion takes more time，but the effect tends to unanimous after7years.