Spatial structure change and comprehensive evaluation of pure Chinese fir forest after interplanting broad-leaved tree species
In order to know about the spatial structure change of Chinese fir pure forest stand,four-tree method was used to build stand spatial unit and five stand spatial structure indexes including angle scale,mingling index,open degree,neighborhood comparison and stand layer index were adopted to analyze the stand spatial structure change of young-and middle-aged pure Chinese fir forest before and after interplanting broad-leaved tree species based on the measured data of six plots of pure Chinese fir forest with different age groups in Fushou Forest Farm,combining qualitative and quantitative analysis methods.Then all indexes were evaluated by using method of multiplication and division.The stand spatial structure indexes were divided into five evaluation levels.The higher the level,the more reasonable the spatial structure of the stand and the more abundant the forest layers.The results showed as follows:(1)Before interplanting broad-leaved trees species,the angle scales of young-and middle-aged stands of pure Chinese fir forest were 0.368 7 and 0.346 4,the mingling indexes were 0.150 7 and 0.062 7,the open degree of were 0.977 8 and 0.433 8,the neighborhood comparison were 0.499 1 and 0.522 5 and the stand layer indexes were 0.249 5 and 0.341 4,respectively.The evaluation index of stand spatial structure ranged from 0.186 2 to 0.387 6,with grade 1 plots number accounting for 16%and grade 2 plots accounting for 84%of the total plots number.(2)After interplanting broad-leaved trees species,the angle scales of young-and middle-aged stands of pure Chinese fir forest were 0.328 9 and 0.219 7,the mingling indexes were 0.385 7 and 0.162 9,the open degree were 1.718 2 and 0.713 6,the neighborhood comparison were 0.406 4 and 0.437 7,and the stand layer indexes were 0.306 3 and 0.512 3,respectively.The evaluation index of stand spatial structure ranged from 0.592 1 to 0.857 3,with grade 4 and grade 5 plot number accounting for 50%of the total plot number,respectivelly.The results could provide a new reference for Chinese fir pure forest interplanting broad-leaved tree species as practice of stand spatial structure optimization management.
Chinese firpure foreststand spatial structurebroad-leaved tree speciesmethod of multiplication and division