Optimization of Carbon Sequestration Management Technology of Pinus kesiya var. langbianensis Natural Forest Based on the Adjustment of Forest Stand Spatial Structure

One hundred and twenty-six trees in the sample plots set up in 2012 were taken as data sources in 2007 and 2012 in the Pu'er area, and intercalation was used as a nurturing measure to establish an intercalation model with the spatial structure of the stand adjusted and optimized and carbon storage as the target. The constraints were angular scale, mixing degree, openness, stand index and competition index of spatial structure, tree size and species diversity of non-spatial structure, and carbon stock change. Nine interharvesting intensity gradients were set, and the interharvesting model was solved with the idea of multi-objective planning. The results showed that the correlation between the spatial structure indexes and the objective function values of Pinus kesiya var. langbianensis natural forest stands was openness > story index > angular scale > mixing degree > competition index; the changes of all parameters in the stands increased with the increase of intercutting intensity. The stand was optimized best at 45% intercutting intensity, with 49 trees harvested, and the diversity of species composition and uniformity of diameter structure of the stand remained unchanged. The degree of intra-forest light transmission increased by 31.27%, the vertical structure richness of the stand increased by 27.68%, the angular scale index value decreased by 19.77%, the spatial segregation of tree species increased by 20.63%, and the competition among trees decreased by 44.27%. The target function value risen from 139.64 to 658.51, which is almost 4.5 times higher than that before the intercutting, and the carbon stock increased by 35.35 t/hm² compared with the previous period. While ensuring the carbon stock of the stand, the performance of the stand in terms of the degree of competition among trees, vertical structure, species isolation and light condition of the stand was significantly improved. The overall stand condition changed to a higher quality direction, which is an essential reference for the sustainable development and management of natural forests and similar stands.