Mi Xiangcheng

The phylogenetic signal of functional traits and their effects on community structure in an evergreen broad-leaved forest: The phylogenetic signal of functional traits and their effects on community structure in an evergreen broad-leaved forest

The phylogenetic conservatism of plant functional traits and its association with community struc- ture are important topics in ecological research. Plant functional traits are simultaneously affected by their evolutionary background, local habitat conditions and large-scale climate. In this study we asked whether functional traits have a significant phylogenetic signal and significantly affect species abundance in a com- munity. For this objective, we used data from a 24 ha Gutianshan forest plot, which included species abun- dance and six functional traits of 156 woody species: leaf nitrogen content, leaf phosphorus content, leaf area, wood density, specific leaf area and seed mass. We found that all functional traits showed significant phylogenetic signal, suggesting that all functional traits are significantly affected by their evolutionary his- tory. We also found that species abundance was correlated with leaf nitrogen content, leaf phosphorus con- tent, leaf area, woody density and specific leaf area except seed mass, suggesting that resource acquisition significantly affects species abundance distribution in a community, and that these functional traits impact

Recovery dynamics of secondary forests with different disturbance inten- sity in the Gutianshan National Nature Reserve

Understanding the underlying processes of secondary forest recovery after disturbances such as logging is essential for biodiversity conservation and ecosystem rehabilitation. We surveyed 12 forest plots (1 ha in size) with different extents of anthropogenic disturbances in the Gutianshan National Nature Reserve and explored the community dynamics of secondary forest recovery by applying multivariate statistical analysis. We found significant differences in community composition among various recovery phases, whereas high similarities of community composition were observed within the same recovery phase. No significant difference in species richness was observed among recovery stages, but species richness tended to increase during the recovery process. Species evenness in Chinese fir forests was relatively low whereas no significant difference occurred in other forests. The main differences in community composition and species diversity were found in the canopy layer. Respective indicator species were found in shrubs and regeneration layers during different recovery phases. The most representative indicator species were deciduous shrubs or heliophilous trees for plantation forests of Chinese fir, evergreen shrubs or small trees for young secondary forests, sub-canopy evergreen trees for old secondary forests, and canopy species for old-growth forests, respectively. Overall, species diversity recovered rigorously. Also the life-form composition of saplings in the same recovery phase presented consistent trends in spite of complex and unpredictable changes in species composition during the recovery process.

Multivariate relationship between tree diversity and aboveground biomass across tree strata in a subtropical evergreen broad-leaved forest

The correlation between primary producer diversity and the productivity (or biomass) of ecosystems is one of the most important and broadly studied relationship in ecology. Ecologists have discussed this relationship from two fundamentally different perspectives. Historically, productivity has been viewed as driver of species diversity. Recently, many studies have demonstrated that diversity can also control, rather than responds to, the production of biomass. These contrasting points of view have led to the debate about whether species diversity is the cause or the consequence of community productivity. Multivariate productivity-diversity hypothesis has been put forward to reconciling this debate. This hypothesis state that: (i) the environmental factors are the direct driver of species that can coexist within an area; (ii) the biomass of the area is directly influenced by the environmental factors that limit production; (iii) the environmental factors indirectly influenced biomass of the area via influencing the species number to coexist within the area that affects how efficiently environmental resources are converted into biomass. To date, empirical support for this hypothesis is scarce, especially for structurally complex terrestrial ecosystems. In this study, we modified multivariate productivity- diversity hypothesis to accommodate complex vertical structure of forest ecosystems, and used structural equation modeling and data from a large evergreen broad-leaved forest dynamic plot (24 hm2 in area) in subtropical China to understand the causal relationships among environmental factors, species richness, dominance and aboveground biomass. Trees were grouped into tow functional groups (overstorey and understorey) in order to improve the ability to detecting the diversity effect. The final model explained 30% and 58% of the variation in aboveground biomass of overstorey and understorey, respectively. Dominance was the most important factor in explaining the variation of aboveground biomass of overstorey, while both species richness and environment factors were the most important factors in explaining the variation of aboveground biomass of understorey. Consistent with the predictions of multivariate productivity-diversity hypothesis, (i) aboveground biomass were directly influenced by the environmental factors in both overstorey and understorey; (ii) environmental factors directly influence tree dominance and species richness of overstorey, but only directly influence species richness of understorey; (iii) environmental factors indirectly influence aboveground biomass of overstorey by influencing dominant, while indirectly influence aboveground biomass of understorey by influencing species richness. Interestingly, species richness was only important to explaining variation in aboveground biomass of understorey. This may be attributed to the low light condition in understorey, which may alleviative competition among trees of understorey. To our knowledge, this study provides the first empirical evidence supporting the multivariate productivity-diversity hypothesis in forest ecosystem thus contributes to extending the generality of this framework. Our result also highlights both dominant species and higher species richness is required to maximizing forest biomass.