Study On Stand Structure Of Protection Forest And Tree Composition Of Economy Forest In Loess Platesu

Protection forest and economic forest were used as the study object, the stand structure and canopy characteristics of protection forest and economic forest were analyzed by methods of sample plot′s surrey and the plant canopy hemispherical photographys system. The results are as follows:(1)On the protection forest,there were 28 species plant,compositae,gramineae and leguminosae were main in all Family In Robinia pseudoacacia plantaions. diameter structure was nearly normal distribution when density of middle-aged stands was 700-900 trees per hectare,smaller stand density had promoted diameter growth,but larger stand density had promoted height growth. middle-aged stands formed better stand structure which stand density was 925 trees per hectare;There were significant difference among canopy indicators of Different Stand Densities.There were 20 species plant,compositae and gramineae were main in all Family In Chinese Pine plantaions. diameter structure was nearly normal distribution when density of young-aged stands was 900 trees per hectare and density of middle-aged stands was 575 trees per hectare. On the same stand age ,smaller stand density had promoted diameter growth and larger stand density had promoted height growth. Young-aged stands and middle -stands could form better stand structure which density was 900 trees per hectare and 500 trees per hectare. There were significant difference among canopy indicators of Different Stand Densities.There were 17 species plant,compositae and gramineae were main in all Family In Platycladus orientalis plantations. diameter structure was nearly normal distribution when density of young-aged stands was 1250 trees per hectare and density of middle-aged stands was 750 trees per hectare. Density of young-aged stands was 800 trees per hectare and density of middle-aged stands was 525 trees per hectare that they formd better stand structure. There were significant difference among canopy indicators of Different Stand Densities.(2)On the economic forest, basal diameter of walnut young growth increased,basal diameter,number of branches and number of branches reduced, with the stand density reduceing. There were significant difference among canopy indicators of middle-aged stands. Better planting spacing of midlle-aged stands was 4m×5m.As the density reduced, basal diameter and number of branches of walnut young growth increased,basal diameter,crown height and crown width of middle-aged stands reduced, basal diameter,height under branch,crown height and crown width of old-growth stands reduced. There were significant difference among canopy indicators of different age forest. Better planting spacing of midlle-aged stands was 3m×5m,its old-growth stands was 3.5m×4.5m.As the density reduced,tree body indexes of almond-apricot and radiant energy,scattering energy of crown interception increased. There were significant difference among canopy indicators,the better planting spacing was 4m×6m.There were significant difference among canopy indicators of jujube. Better planting spacing of young-aged stands was 2m×4m,its middle-growth stands was 3m×4m.