Analysis And Evaluation Of The Spatial Structure Of Four Typical Forest Stands In Jindong Forest Farm

Reasonable spatial structure of forest stands can determine the direction of their development and maintain the stability of their ecosystem.The spatial structure of forest stands is an easily controllable factor that can intuitively express the forest structure and meet the increasing demand for precise information about trees in forest management.By analyzing and evaluating the spatial structure of different types of forest stands,scientifically reasonable management plans can be formulated to maximize the ecological and social benefits of forests.In this study,four typical forest stands(Phoebe bournei pure stand,Phoebe bourneiCunninghamia lanceolata mixed stand,Phoebe bournei-Schima superba mixed stand,and Cunninghamia lanceolata pure stand)in Jindong Forest Farm in Yongzhou City,Hunan Province,were selected as research objects.Based on the four-tree method,the spatial structure units of forest stands were determined,and rough set theory was used to screen the spatial structure indices of forest stands.The spatial structure of forest stands was analyzed in five aspects:stand distribution pattern,degree of stand openness,stand isolation,stand layer structure and stand competition.Multi-objective planning was carried out using the multiplication and division method,and the key factors affecting the spatial structure of forest stands were determined based on the size of the internal standard deviation of each spatial structure parameter using the idea of coefficient of variation method.Finally,the evaluation index of spatial structure of forest stands was proposed to evaluate the current status of forest stands,with the aim of proposing precise and feasible management measures for the four typical forest stands in Jindong Forest Farm.The main conclusions are as follows:(1)The spatial structure index attributes of four typical forest stands in Jindong Forest Farm were reduced.Rough set theory was applied to select the spatial structure index attributes,and four redundant attributes with low importance,including diameter at breast height,size ratio,spatial density index,and degree of freedom,were deleted.The resulting forest spatial structure index attributes were reduced to five different attributes,including angular scale,simple mixing degree,openness degree,competition index,and forest layer index,with importance values of 0.084,0.043,0.043,0.096,and 0.124,respectively.These were the selected forest spatial structure index attributes.(2)Analysis of the stand structure characteristics of four typical stands in the Jindong forest.The angular scales were 0.5653 in the pure forest of Phoebebournei,0.6147 and 0.5771 in the mixed forest of Phoebebournei-Schima superba and 0.5913 in the mixed forest of Phoebebournei-Fir,and 0.2744 in the mixed forest of Phoebebournei-Fir,all of which were randomly distributed in clusters or close to clusters.The openness of Phoebebournei-Fir mixed forest and Phoebebournei-Fir pure forest is 0.2606 and 0.2348,and there is insufficient space for the growth of trees in each stand type;The stand index of the pure forest is 0.2904,the stand index of the mixed forest is 0.2453,the stand index of the mixed forest is 0.2241,the stand index of the mixed forest is 0.1704,and the stand index of the mixed forest is generally low.(3)Intra-and interspecific competition analysis of four typical forest stands in Jindong Forest.The results showed that the average intra-species competition index by species showed that Phoebebournei>Schima superba>Cinnamomum camphora in Phoebebournei pure stands;Schima superba>Phoebebournei>Cinnamomum camphora in Phoebebournei-Schima superba mixed stands,Phoebebournei>Fir in PhoebebourneiSugi mixed stands;and Fir>Schima superba in Fir pure stands.The average competition index among different tree species was used as a criterion to compare the size,and the competition intensity of each species in the pure forest of Phoebebournei was Balsam fir>Schima superba>Phoebebournei;in the mixed forest of Phoebebournei-Schima superba,Fir>Balsam fir>Phoebebournei>Schima superba;in the mixed forest of Phoebebournei-Fir,Schima superba>Taxus wallichiana>Liquidambar formosana Hance>Phoebebournei>Sassafras tzumu>Fir>Balsam fir;and in the pure forest of Fir,Schima superba>Fir.(4)Evaluation of the spatial structure of typical stands in four typical forest stands in Jindong Forestry.Multiplication and division method was used for multi-objective planning,the idea of variation coefficient method was used to determine the parameter weights,and the stand spatial structure evaluation index was proposed to evaluate the current status of the stands.The results showed that the evaluation indices of Phoebebournei pure forest were 0.0926-0.2357;in Phoebebournei-Schima superba mixed forest,the evaluation indices were between 0.1712-0.2762;in Phoebebournei-Fir mixed forest,the evaluation indices were 0.1951-0.3623;in Fir pure forest The evaluation indices in pure fir forests ranged from 0.1458-0.3443,and the evaluation levels were all classified as 1 and 2.This indicates that the spatial structure of the four typical forest stands in Jindong Forestry is still far from the ideal state and needs to be optimized.(5)Suggestions for spatial structure adjustment of the four typical forest stands in Jindong Forestry.According to the comprehensive evaluation results,it is found that the rank scores of the four stand types are low,and there is still a gap between them and the ideal spatial structure of the stands,so certain adjustment measures are needed.In order to improve the overall level of stand spatial structure in each stand,the tree species structure should be adjusted to maintain the healthy growth of target trees in Phoebebournei pure forests and fir pure forests;in Phoebebournei-Schima superba mixed forests,priority should be given to adjusting the spatial distribution pattern of stands;in PhoebebourneiFir mixed forests,priority should be given to adjusting the stand layer structure of stands.