Study On Stand Structure During Different Succession Stages In Degraded Spruce-Fir Forests Of Changbai Mountains

This paper has the degraded spruce-fir forest as the object of research, which is located in Jingoulin forest farm, Wangqing forestry bureau, Jilin province. Stand structure of polar-birch secondary forests, spruce-fir and broadleaved mixed forests, spruce-fir mixed forests and near primitive spruce-fir forests, which are representative of the forest communities in Changbai Mountains, were analyzed. The detailed study contents included species composition, volume structure and diameter structure, the spatial distribution patterns and associations, mingling degree of spatial structure, which would be provide scientific basis for spruce-fir forest management of this study area. The brief results were as follows:(1) The type of tree species of forest stands was similar during different succession stages, but species compositions were different. In polar-birch secondary forest, Betula platyphylla had larger abundance than other species’, while Pinus koraiensis, Picea koraiensis, Abies nephrolepis were showed great number in species composition of broadleaved mixed forests. The total volume of stand was increased gradually from polar-birch secondary forest to near primitive spruce-fir forests, volume of pioneer species and small diameter wood accounted for most of the total stand volume in polar-birch secondary forest, the largest proportion of stand volume were climax species and large diameter wood in near primitive spruce-fir forest. According to the results, methods of replanting conifer and protecting broadleaf, and suggestions to improve the volume structure were preliminarily put forward.(2) The finite mixture Weibull model, negative exponential model and Weibull model were applied to model tree diameter distributions. The diameter distributions were presented multimodal and rotated-sigmoid of irregular shapes. The statistical methods showed the fitting effect of finite mixture Weibull model was best, especially in modeling bimodal and rotated-sigmoid distributions, then was the Weibull model’s, and negative exponential model’s was the last.(3) In the research of spatial distribution patterns and associations of different stand, the aggregation degree of dominant tree species in polar-birch secondary forest decreased with increasing the layers’ height. At small scales, Pinus koraiensis in lower layer was positively correlated with Betula platyphylla and Pinus koraiensis in higher layer, but negatively correlated with Abies nephrolepis. The negative associations appeared widely between two species among Pinus koraiensis, Betula costata and Betula platyphylla, then suggestions for replanting of Pinus koraiensis were given. From the spruce-fir and broadleaved mixed forest to the spruce-fir mixed forest and near primitive spruce-fir forest, the aggregated distribution decreased, while the random and regular distributions increased in all major species.(4) The average mingling degree of secondary forest was higher than other forests, and the stand mingling degree was gradually increased from spruce-fir and broadleaved mixed forest to spruce-fir mixed forest and near primitive spruce-fir forest. The mingling degrees of four forest stands were in the range of0.4-0.6, which belongs to the moderate mixed degree.