Studying The Effects Of Thinning On The Tructureand Health Of Different Forest Types

Forest thinning is the important content of conducting scientific forest operation and management. It is the important way to optimize the layout of forest spatial structure, improve the forest quality, promote tree growth, improve forest productivity, enhance the resilience of forest ecosystems, maintain the forest ecosystem health and improve the forest ecosystem ecological functions.The study is based on the theory of sustainable forest management and near-natural forest management theory, targeted to Larix, Armand pine, Pinus tabulaeformis and Quercus aliena var.acuteserrata which are representative forest types of Qinling Mountain, we set a total of 20 plots(specifications are rectangular, size of 20m×30m) in Xunyangba forest of Ningdong forestry of Shanxi Province and Huoditang teaching experimental forest of Northwest A & F University respectively to study the influence of forest thinning on woodland tree DBH diameter class distribution ; the influence of forest thinning for on the height of forest trees; the influence of forest thinning on forest species composition; the influence of forest thinning on forest quality; the influence of forest thinning on forest health status. The results showed that:In terms of the distribution of forest diameter class distribution, it is diameter class distribution before and after thining in the four types of forest.There is not significant influence of intermediating cutting on forest heights,.Intermediating Thinning has a significant influence on forest plantation, especially the composition of purpose species of trees and dominant trees.Thinning greatly improved the quality of forest stands of the four kinds of forests.Thinning has an great effect on improving forest health. For Larch.This study showed that the thinning did not change the diameter class distribution pattern of the four kinds of trees, it reduced the tree density of each diameter class, expanded the nutrition space of plant , increased the proportion of the growing period of trees and woodl and growth potential, reduced the proportion of affected trees, improved stand health, caused the increasing of light-preferring and nutrient-preferring plant species and improved the productivity and resistance to natural disasters of the stand, but there is limited influence on the height of medium aged trees...