ObjectiveThe effects of different thinning patterns on forest spatial structure were evaluated by analyzing the changes of main indicators of spatial structure and comprehensive spatial structure index of Quercus mongolica secondary forests (oak forest) before and after thinning.

MethodNine permanent plots with an area of 1 ha were established in the oak forest in Wangqing, Jilin Province of northeastern China. Three kinds of treatments were carried out by random grouping, namely traditional management (T1), crop tree management with density 1 (T2) and crop tree management with density 2 (T3). The spatial structure variations of the crop trees and forest stand before and after the cutting operation were analyzed by mingling degree, uniform angle index, neighborhood comparison and crowding degree. The above four indicators were used to construct the comprehensive spatial structure index (CSSI) to comprehensively evaluate the response of oak secondary forest to the management measures.

ResultThe results showed that the mean mingling degree, neighborhood comparison and crowding degree of the crop trees in T2 and T3 were improved after competitors cutting, while the change of mean uniform angle index was not obvious. From the perspective of the effects of different measures on the stand spatial structure, the mean mingling degree, uniform angle index and crowding degree of the target stands were all improved after cutting, while the neighborhood comparison variation was not pronounced. CSSI of all stands was increased by T3 > T2 > T1.

ConclusionThe spatial structure of crop trees was optimized by competitor cutting, and the spatial structure of all stands was optimized by 3 kinds of thinning. The improvement of the spatial structure of the thinning based on the crop tree management is better than the traditional thinning. T3 is most beneficial to the optimization of the spatial structure of the stand.