Dynamic thinning system for larch plantation

Abstract

Systematic researches were carried out in dahurian larch (Larix gmelini) plantation in the spring of 1958 at Maoershan Forest Farm attached to Northeast Forestry University. First of all, a new tree classification method, relative classification in small group, was presented. Each small group was composed of one tree in the center and six adjacent trees, which formed a hexagon in space. All these seven trees, then, can be divided into five classes such as class A, class B, class C. class D and class E respectively. For the convenience of comparison, the stand used for the trial was divided into five experimental plots in which the thinning intensity for each plot was controlled as follows: 10% for the first plot; 20% for the second plot; 30% for the third plot; 40% for the fourth plot and the fifth plot without thinning for comparison. Thinning operation was carried out according to the principle of reserving A-class trees, cutting B-class trees in the intensity as required, releasing C-class trees and removing D and E class trees. Through 14 years study, the result shows that if the stand volume of contrast plot is considered as 100% after the first thinning, the volume of other plots are 114. 9% for the first plot, 128.4% for the second plot, 133.1% for the third plot and 118. 5% for the fourth plot respectively. Meanwhile, biomass and increment of diameter can also be increased significantly after thinning by this method.