Evaluation of Spatial Structure and Homogeneity of Bamboo and Broad-Leaved Mixed Forest

Bamboo and broad-leaved mixed forest is a kind of forestry management that can effectively improve the ecology of bamboo forests. The aerial structure of the stand can reflect the growth status of the stand, as well as the spatial structure of the stand with respect to maintaining and improving the basis of the stand structure. However, the lack of quantitative studies on how different mixing ratios affect the stand spatial structure of bamboo and broad hybrid forests has further disturbed the development of bamboo and broad-leaved mixed-forest management. In this study, we used 10 bamboo and broad mixed forests with different ratios as the research object, determined the stand spatial structure unit by using the weighted Delaunay triangular network, calculated the stand spatial-homogeneity index from the vertical spatial structure of the stand, horizontal spatial structure, and competition, and constructed the stand spatial-homogeneity evaluation system by combining it with the forest health grading system and the rank classification method of the near-natural forest management, dividing it into five evaluation classes. It was divided into five evaluation levels. Finally, a regression model was used to elucidate the effects of stand spatial homogeneity on moso bamboo (Phyllostachys pubescens) biomass. The results showed that the spatial homogeneity of No. 1 (5%–10% mixed) and No. 3 (15%–20%) samples was classified into five grades; No. 2 (10%–15%) samples were classified into four grades; No. 4 (20%–25%) and No. 6 (30%–35%) samples were classified into three grades; No. 5 (25%–30%) samples were classified into two grades; and Nos. 7–10 (more than 35%) samples were all classified into one grade. It was also found that both the degree of hybridization and the competition index in the bamboo and broad-leaved mixed forest showed highly significant negative correlation with the spatial homogeneity index of the stand and the moso bamboo biomass, while the spatial density index showed highly significant positive correlation with the spatial homogeneity index of the stand and the moso bamboo biomass. From the viewpoint of management purpose, for the management of bamboo and broad-leaved mixed forest with economic benefits, the mixing ratio should be 5%–10% and 25%–35%; for the management of bamboo and broad-leaved mixed forest with ecological benefits, the mixing ratio should be more than 35%; and for the management purpose of balancing ecological benefits and economic benefits, the mixing ratio should be 10%–25%.