Niche of woody plant populations in Picea purpurea community in the upper Taohe River

Abstract

The niche of plant populations is affected by the environment, species characteristics and anthropogenic disturbance. Picea purpurea, as a major constructive species in the northeastern Qinghai-Tibetan Plateau, had been severely damaged. Although the national project for the protection of natural forests has promoted the recovery of its community, its structure, survival status, development trend, and the factors affecting it are still unclear. We selected P. purpurea communities in Zecha, Dayugou and Yeliguan forest zones at different altitudes and disturbance levels. We analyzed niche characteristics of the woody plants and the relationship between niche and altitude, and disturbance. P. purpurea has absolute advantages as a constructive species, and its population dominance and niche width in the tree layer show a decreasing trend with decreasing altitude, there is niche overlap between all species pairs. In the shrub layer, the dominant species are mostly Caprifoliaceae and Rosaceae besides P. purpurea seedlings, the proportion of species pairs with niche overlap is YLG>ZC>DYG, and all appeared niche divergence and convergence species pairs. In addition, P. purpurea seedlings had niche overlap with most woody species, and this overlap index was the highest. The mean values of the niche overlap index between species in the tree and shrub layers were all YLG>DYG>ZC. The niche overlap index between species in the tree layer was greater than that in the shrub layer in the same forest zones, indicating that the tree layer is more stable than the shrub layer, providing evidence that niche overlap maintains community stability. Regression analyses showed that minimum temperature was the main factor affecting dominance, niche, niche overlap and shrub layer species richness of the P. purpurea population. Disturbance did not significantly affect dominance and niche of P. purpurea seedling populations, but promoted niche differentiation of shrub layer species. We conclude that the P. purpurea community is mainly influenced by altitude and anthropogenic disturbance. Altitude-induced climatic variation fundamentally determines the distinct community composition and population niche. Anthropogenic disturbance has altered habitat heterogeneity and enriched community structure. Furthermore, the P. purpurea populations show a trend towards expansion. Understanding the structure and niche characteristics of P. purpurea communities on different environmental gradients enriches our ideas for implementing vegetation restoration and sustainable forest management in subalpine zones in the context of climate change, and is conducive to improving the conservation capacity of this population or community type.