Determinants of mortality in a mixed broad-leaved Korean pine forest in northeastern China

Empirical analyses of forest dynamics are important for understanding various ecological processes underlying particular forest communities, among which tree mortality is considered a key process driven by many local factors. To evaluate the effects of tree size, as well as biotic and abiotic factors on tree mortality, we compared species-specific mortality rates in a 21-ha temperate multi-species natural forest in northeastern China, where all trees had been mapped. Our study shows that the mortality rates are highly variable among the different tree species and the influence of habitat preference on the mortality rate of a species across habitats was insignificant. Using generalized linear mixed-effects models, we further found that among the drivers of tree survival, tree size had the strongest effect across different species. There are significant negative relationships between the basal area of conspecific neighbors and tree survival at the community level across almost all the guilds. Regarding abiotic factors, elevation had a greater effect on tree survival than other topographic variables did. Abiotic factors affected shrubs more than tall canopy species in terms of survival rate. Our study suggests that tree size, density-dependent effects and niche partitioning contribute to the regulation of survival pattern of temperate forest communities, but the relative importance of these factors varies greatly among guilds and species. This study has shown that it is essential to consider the relative importance of both, intrinsic (tree size) and extrinsic (biotic and abiotic) factors in analyzing tree mortality.