Influence of Different Topographic Conditions on theConstructive Species Coexistence Mechanismof Mixed Forest of Larch and Spruce

【Objective】Exploration on the mechanisms of species coexistence in the environment with limited resources has always been the core problem of community ecology.【Methods】A study was conducted on the mixed forest of Siberian larch-Siberian spruce in the mountainous forest area of Fuyun area. Based on the characteristics of coenology of mixed forest, the influence of the environmental factors (altitude, slope, aspect and slope position) on the distribution of community species and the morphological characteristics of the constructive species were studied by comparison analysis method, in order to explain the constructive species coexistence of the mixed forest of larch and spruce in the study area. 【Result】The results showed that the niche widths of Siberian larch and Siberian spruce were higher than those of other accompanying species; however, both of the diameter structures of Siberian larch and Siberian spruce showed aging trends. Godron coordinate calculation results also showed that the community stability coordinate was (39, 61), which was 26.87 Euclidean distance downward compared with the ideal stability point coordinate (20, 80), indicating that the stability of the mixed forest community was relatively low. The topographic conditions (elevation, slope position, slope, and aspect) ofconstructive species were the important factors affecting the four-phase morphological characteristics (DBH, tree height, canopy area, and number of plants) of the two constructing tree species.【Conclusion】The habitat heterogeneity such as elevation, slope, slope position and aspect of Fuyun mountainous area affects the niche of Siberian larch and Siberian spruce, and maintains the long-term coexistence of these two species in mixed forest community.