Study On Spatial Structure Diversity And Selective Cutting Decision Model Of Larch-spruce-fir Stands

In order to study on the recovery and protection of over-logged forests, the structure of larch-spruce-fir stands was analyzed by appropriate diversity indices and spatial structure parameters to confirm the species diversity status with survey data of six plots. The spatial structure diversity of larch-spruce-fir stands were analyzed based on the calculation of tree species spatial status, spatial diversity index and competition index of intersection angle. Optimization decision model was established by structure-based forest management to simulate and analysis larch-spruce-fir stands of Jin Gouling forest farm on the stand scale. The research would provide theoretical reference for the forest comprehensive management. The main research conclusions are as follows:(1) There was little difference between larch-spruce-fir stands with different composition of larch. The major dominant species of larch-spruce-fir stands were larch, fir, et al. There were more than 11 tree species in each plot. Within tree species diversity indices of six plots, the Shannon-Wiener>Simpson. Weibull model has high fitting accuracy to be applied for the tree diameter distributions in study areas, R2 were all above 0.7.(2) The distribution pattern of mixed forests and relatively pure forest were mainly at random. The accuracy of the description of neighboring tree distribution state was improved with a combination of uniform angle index and spatial density index. The average open degree of stands was 0.22. Thus, there is insufficient space for the trees’growing. The open degrees can describe the luminous environment of larch-spruce-fir stands effectively. The segregation of tree species in all stands was high. The heterogeneity of DBH in all stands was low, and the size of the tree was in the middle level of differentiation.(3) The difference between relatively pure forest and mixed forest was significant. The frequency of the trees with random distribution pattern and high mingling, random distribution pattern and middle dominance degree, middle dominance degree and high mingling in mixed forest were higher than those of relatively pure forest. Compared with the simple mixed degree, the spatial diversity index could demonstrate the difference of spatial configuration of the tree species between the relatively pure and mixed forest of larch-spruce-fir better. The spatial diversity index of relatively pure forest was lower than that of the mixed forest significantly. The larch was in a dominant position of the competition in 6 sample plots. The structure of a stand with 30% of Larch, the needle broad ratio of 8:2 and the vegetation density of 800 could be one of the adjustment direction of the larch-spruce-fir stands in this region.(4) The composite spatial structure index ranges between 0.028-1.262. According to the associated degree and priority, each spatial structure index factor was associated with spatial density index, uniform angle index, open degrees, mean directional index, species space status, diameter dominance, competition index of intersection angle. The harvesting model which were established in this paper can play an effective role in the management of larch-spruce-fir stands and the optimization of spatial structure diversity. From the bivariate distribution of structural parameters, we can see the quantitative characteristics and distribution of the different combinations simutaneously, which has stronger operability in practice of forest management.