Effects of thinning on the habitat of natural mixed broadleaf-conifer secondary forest in Xiaoxing'an Mountains of northeastern China

Taking the natural mixed broadleaf-conifer secondary forest in Xiaoxing an Mountains area of northeastern China as the research object, different thinning intensities and different cutting widths were carried out, and 38 indices involving the factors of soil, litter characteristics, species diversity as well as canopy structure were analysed. The index weight was gotten by using subjective and objective weighting method, the subjective weight was determined by analytic hierarchy process (AHP), and the objective weight was determined by entropy weight method, using the method of minimum information entropy to determine the combined weight. Finally, the habitat factors were evaluated and the comprehensive evaluation was taken. The results showed that: it got the weight of the habitat factor by using the combined weight method, the factors ordered by importance were soil chemical property (0.370), litter water holding capacity (0.231), canopy structure (0.166), species diversity (0.129), soil physical property (0.104). The effects of different thinning intensities and cutting widths on the habitat factors were different. Litter water holding capacity was the first-rate when the thinning intensity was 15% with 10 m bandwidth, the comprehensive evaluation value was 3.510. When thinning intensity was 20% with 18 m bandwidth, the soil chemical property and the forest canopy structure were the best, the comprehensive evaluation values were 2.796 and 0.953; In condition of 30% thinning intensity, the species diversity degree was the best when the thinning bandwidth was 10 m, the comprehensive evaluation value was 1.820; when the thinning bandwidth was 18 m, the soil physical property was better than the rest of sample plots, the comprehensive evaluation value was 7.943. Through the comprehensive evaluation, it was the most suitable forest habitat for biological survival when thinning intensity was 20% with 18 m bandwidth of the natural mixed stand in Xiaoxing'an Mountains. On the whole, thinning can greatly improve the forest habitat and provide a good living environment, this study provides a good theoretical basis for the ecological management of natural secondary forests.