It is well known that evergreen and deciduous species have different functional traits and utilize different strategies in growth and adaptation to environments, however little work has been done to elucidate whether leaf habit mediate the effect of trait-environment interactions on plant performance. Here we wanted to illuminate whether relative growth rate of deciduous and evergreen species depended on multiple trait-environment interactions. We measured eight leaf traits of 1230 individuals from 25 species and collected topographic factors, edaphic variables and competition index in a subtropic evergreen and deciduous mixed forest. Then we modeled plant relative growth rate with high-order trait-environment interactions for evergreen and deciduous species respectively using generalized linear mixed model and visualized the difference between leaf habits. Results showed that leaf habits were divided by trait PC1 (41.8%) which was related to leaf lifespan and resource acquisition. We found that trait-environment interactions improved growth predictions for both leaf habits but the optimal models for them were different. Moreover, the explanatory power of deciduous species models was always higher than that of evergreens. These results indicated that leaf habits with different life history strategies were reflected by trait-environment interactions. We emphasized the importance of leaf habits in explaining forest productivity and functions, and future research should focus on the effects of leaf habits on other demographic metrics and spatial patterns to solve the coexistence of the two leaf habits in mixed forests.

The early growth stage of plants is vital to community diversity and community regeneration. Understandably, it is critical to explore the mechanisms underpinning the spatial and temporal dynamic patterns of seedling survival and growth. The Janzen--Connell hypothesis predicts that conspecific density dependence lowers the survival of conspecific seedlings by attracting specialist natural enemies, promoting the recruitment and performance of heterospecific neighbors. Recent work has underscored how this conspecific negative density dependence may be mediated by mutualists -- such as how arbuscular mycorrhizal fungi may mediate the accrual of host-specific pathogens beneath the crown of conspecific. Aboveground mutualist and enemy interactions exist as well, however, and may provide useful insight into density dependence that are as of yet unexplored. Using a long-term seedling demographic dataset in a subtropical forest plot in central China, we found that a mutualist association with ants had significant positive effects on seedling survival, but a negative effect on seedling growth. We also confirmed that conspecific neighborhoods had a significant negative effect on seedling survival, confirming that the Janzen-Connell hypothesis may influence community composition in the subtropical forest. Overall, our findings suggested that ants and conspecific neighborhoods played important but inverse roles on seedling survival and growth, which indicated that ants may mediate conspecific negative density dependence at community level to some extent.

Phylogenetic trees have been extensively used in community ecology. However, how the phylogenetic reconstruction affects ecological inferences is poorly understood. In this study, we reconstructed three different types of phylogenetic trees (a synthetic-tree generated using VPhylomaker, a barcode-tree generated using rbcL+matK+trnH-psbA and a genome-tree generated from plastid genomes) that represented an increasing level of phylogenetic resolution among 580 woody plant species from six dynamic plots in subtropical evergreen broadleaved forests of China. We then evaluated the performance of each phylogeny in estimations of community phylogenetic structure, turnover and phylogenetic signal in functional traits. As expected, the genome-tree was most resolved and most supported for relationships among species. For local phylogenetic structure, the three trees showed consistent results with Faith’s PD and MPD; however, only the synthetic-tree produced significant clustering patterns using MNTD for some plots. For phylogenetic turnover, contrasting results between the molecular trees and the synthetic-tree occurred only with nearest neighbor distance. The barcode-tree agreed more with the genome-tree than the synthetic-tree for both phylogenetic structure and turnover. For functional traits, both the barcode-tree and genome-tree detected phylogenetic signal in maximum height, but only the genome-tree detected signal in leaf width. This is the first study that uses plastid genomes in large-scale community phylogenetics. Our results highlight the outperformance of genome-trees over barcode-trees and synthetic-trees for the analyses studied here. Our results also point to the possibility of Type I and II errors in estimation of phylogenetic structure and turnover and detection of phylogenetic signal when using synthetic-trees.