Trait-mediated neighbor effects on plant survival depend on life stages and stage-specific traits in a temperate forest

Abstract

Among the multiple ecological processes that determine species coexistence and community dynamics, conspecific negative density dependence (CNDD) and niche partitioning are perhaps among the most important. However, the relative strength of these mechanisms may change across life stages and depend on species ecological strategies. We used a dataset that includes information on stage-specific functional traits and a long-term, spatially explicit data of plant survival including 7971 individuals and 41 species monitored for seedling and adult life stages to examine the relative role of these mechanisms influencing individual survival across ontogenetic stages in a 9-ha temperate forest plot in China. Our results showed that for seedlings, CNDD became weaker for species with larger leaf area, while for adults, the conspecific neighbors had a positive effect on survival and this effect became stronger with decreasing seed mass. Also, the results examing the effects of neighboring heterospecifics suggest a prevalence of niche partitioning at the seedling stage but a prevalence of environmental filtering or hierarchical competition for the adult stage. In particular, the strength of these processes at the adult life stage increased with higher maximum height and smaller specific leaf area. Finally, we found that the effect of traits on individual survival for seedling and adult life stages was dependent on both the prevalence of conspecifics and functional diversity of heterospecifics in the neighborhood. Overall, our results demonstrates that ecological processes tend to have a stronger diversifying effect for seedlings than for adults and these effects depend on stage-specific species traits. Considering trait variation and their interacting effects with biotic factors across life stages provides further insights into ecological mechanisms shaping plant communities and driving its dynamics.