The assembly and interactions of tree species in tropical forests based on spatial analysis

Abstract

AbstractTree species were assembled into forest communities by various processes, and it was found that trees are spatially arranged in a community by the abiotic and biotic conditions within that community. Here, we explore the abiotic processes and biotic interactions in the spatial patterning of tree species across six old‐growth forest types in a tropical nature reserve. Four spatial point process models (the homogeneous Poisson process, inhomogeneous Poisson process, homogeneous Thomas process, and inhomogeneous Thomas process) were used to evaluate the potential contribution of the random processes, habitat heterogeneity, dispersal limitation, and the joint effects of dispersal and habitat heterogeneity to the formation of the spatial patterns of tree species. A combination of the null model and size–distance regression analysis was applied to assess the effect of competition and facilitation on the tree species assembly. We found that the homogeneous and inhomogeneous Thomas processes were the best models for describing the spatial patterns of more than 85% tree species across the six tropical forests. The combination of the null model and size–distance regression analysis showed that 37–44% of tree species were affected by competition and 9–24% of tree species were affected by facilitation across the six tropical forest types. Competition was the dominant form of species interactions in forests with mild abiotic conditions such as the tropical montane rain forest and tropical lowland rain forest. Meanwhile, facilitation was the most important biotic interaction in the abiotically harsh tropical montane dwarf forest on mountaintops. Our study suggests that dispersal limitation and the joint effects of dispersal and habitat heterogeneity were the dominant abiotic processes in controlling the spatial patterning of trees in tropical forests. Moreover, the relative importance of competition and facilitation in the assembly of the tree species varied among the forest types with different abiotic conditions.