Variation of the biotic neighbourhood and topographic effects on tree survival in an old-growth temperate forest

Aims: Tree mortality can determine forest dynamics and succession, alter nutrient cycling and contribute to tree species co-existence. Understanding the mechanisms that maintain species diversity is a central goal of community ecology. In this study, we incorporated survival data from a 10-yr interval census to determine whether there is significant interspecies variation in the effects of biotic neighbourhood variables and whether there is significant spatial variation in the effects of topographic variables on tree survival in a broadleaved-Korean pine temperate forest. Location: Temperate forest, northeast China. Methods: We used GLMM and geographically weighted GLM as well as their corresponding test approaches to determine whether there is significant interspecies variation in the effects of biotic neighbourhood variables over variable neighbourhood radii and whether there is significant spatial variation in the effects of topographic variables on tree survival across multiple spatial scales in an old-growth temperate forest dynamics plot in northeast China. Results: Our results showed that the effects of neighbourhood variables on tree survival varied among species and effects of topography varied over space. However, the results depended on the neighbourhood radius and spatial scale. The neighbourhood radius affected detection of variation in neighbourhood effects among species, and the spatial scale similarly affected detection of spatial variation in the effects of topography. The effect of conspecific neighbour density on survival varied more widely among species than that of the average phylogenetic dissimilarity of heterospecific neighbours, regardless of the neighbourhood radius. Moreover, the effect of elevation varied more widely over space than those of convexity and hill shade at any quadrat scale. Conclusions: Our findings highlight that future studies should account for variations in the neighbourhood radius among species and/or circumstances as well as the spatial scale when assessing factors that contribute to species co-existence in long-lived organisms. Species leaf phenology, shade and drought tolerance and environmental filtering may explain these variations in the effects of neighbourhood and topographic variables on tree survival. Overall, our results indicate that both density dependence and resource niche partitioning are important mechanisms for maintaining biodiversity in this broad-leaved Korean pine temperate forest.