Most dioecious plants are trees. However, because of the difficulty in determining sex from vegetative morphology, previous investigations of the sex ratios of dioecious trees were limited to flowering individuals, leading to inadequate and potentially unreliable data on patterns of sex ratios and the underlying mechanisms driving their variation. Here, we applied sex-specific molecular markers to investigate the sex ratio of a fully mapped population of the dioecious tree Diospyros morrisiana (Ebenaceae) in a subtropical forest. We also investigated the sexual dimorphism of life-history traits and spatial association between male and female trees to determine potential processes shaping the sex ratio at different life stages. Molecular sexing revealed a female-biased population sex ratio for this D. morrisiana population, contrasting with the male-biased operational (i.e., flowering) sex ratio. The sex ratio of D. morrisiana shifted from female-biased to male-biased over older life stages. We found that reproduction had a larger impact on the growth of female trees, which may account for the ontogenetic shift in sex ratio. There was no evidence of spatial segregation of the sexes beyond a scale of 2 m. Through molecular sexing of all individuals across all life stages, our work revealed for the first time a shift from a female- to a male-biased sex ratio in a huge population of a dioecious tree species. To better understand variation in sex ratios and the underlying mechanisms in dioecious trees, the sex of non-flowering and juvenile individuals should be included in future studies.

Soil carbon (C) cycling plays critical role in regulating global C budget and atmosphere CO2 concentration. The ongoing global warming potentially accelerates soil C loss induced by microbial respiration (MR) and makes soil a large C source to atmosphere. Quantifying the drivers of MR and its response to rising temperature (also called temperature sensitivity, Q10) is a high priority in order to improve the modelling and prediction of terrestrial C cycle under global warming. In this study, we applied a standardized soil sampling along 9 gradients from 400 m to 1100 m in a subtropical forest in South China, and conducted the incubation experiment at the same temperature ranges (from 10 °C to 25 °C) to measure MR and Q10, then the measured MR was adjusted by the field temperature of sampling site. Our objectives were to examine the response of MR and Q10 to the environmental change induced by elevational gradients in the subtropical forest, and then quantify their main drivers. We totally collected 54 abiotic and biotic factors relative to the MR and Q10. Our results showed that the incubated MR increased from low to high elevation. However, significantly elevational trend of the adjusted MR was not examined after adjusted by the field temperature of sampling sites, due to the tradeoff between increasing soil C concentration and declining temperature as elevation increased. We further found that the 9 elevational gradients did not cause significant change of Q10. The variation of Q10 was negatively dominated by soil C quality. Since climate warming is predicted faster at high elevation than that at low elevation, C loss from high elevation might be accelerated in the future and need more attentions in the further studies

Vertical root segregation can be a key underpinning of species co-existence through below-ground niche partitioning but has rarely been tested in diverse forest communities. We randomly sampled > 4000 root samples from 625 0-30 cm soil profiles in a subtropical forest in China to determine the degree of vertical root segregation among 109 woody species and rooting plasticity in response to edaphic heterogeneity and root neighbours. Over 85% of species were predominantly distributed in the 0-10 cm soil zone, exhibiting low and inconsistent rooting plasticity in response to either edaphic heterogeneity or root neighbours. There was no evidence of vertical root segregation among co-occurring species. Contrastingly, the increase of one species’ root abundance tended to increase, but not reduce other species’ root abundance within soil zones. These findings suggest that interspecific differentiation of resource acquisition strategies might be more important than root segregation in mediating species co-existence in diverse forests.

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.