Stand structure dynamics and effect evaluation after thinning

Abstract

Stand structure, a fundamental part of forests, has generally been well studied, but it has not been fully explored as influenced by thinning and recovery intervals. Thus, four treatments, control (CK), light thinning (LT), moderate thinning (MT), and heavy thinning (HT), were applied to explore the spatial structural dynamics after thinning from 2019 to 2022. In this study, stand spatial structure represented by four structural parameters: uniform angle index, mingling index, neighborhood comparison index and crowding degree index. For analyzing of the structural composition of the stands, the frequencies of N-variate distributions are flexibly combined with four structure parameters. Additionally, this study explored the dynamic changes of spatial structure at the individual level. The influence of regenerated trees and dead trees is higher than that of live trees. The regenerated trees reduced and flowed to tiny, sparse and randomly distributed individuals, which were surrounded by 3 or 4 different species, with an increase in thinning intensities. In less disturbed plots, the uniform angle index had the highest priority for adjustment in structure-based forest management, followed by the mingling index and the crowding degree index, and finally the neighborhood comparison index. However, the importance of crowding degree reduced with the increasing of thinning intensity. The positive effect of thinning on the spatial structure of stands was demonstrated in this study. In the long term, the MT treatment is more beneficial to sustainable forest management than LT and HT treatments.