Direct and indirect effects of climate on richness drive the latitudinal diversity gradient in forest trees

Data accessibility statement: Full census data are available upon reasonable request from the ForestGEO data portal, http://ctfs.si.edu/datarequest/ We thank Margie Mayfield, three anonymous reviewers and Jacob Weiner for constructive comments on the manuscript. This study was financially supported by the National Key R&D Program of China (2017YFC0506100), the National Natural Science Foundation of China (31622014 and 31570426), and the Fundamental Research Funds for the Central Universities (17lgzd24) to CC. XW was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB3103). DS was supported by the Czech Science Foundation (grant no. 16-26369S). Yves Rosseel provided us valuable suggestions on using the lavaan package conducting SEM analyses. Funding and citation information for each forest plot is available in the Supplementary Information Text 1.Peer reviewedPostprin

Contribution of conspecific soil microorganisms to tree seedling light responses: Insights from two tropical species with contrasting shade tolerance

International audienceLight intensity drives whole-plant carbon gain, with consequences for biomass production and plant community dynamics in forest systems. Recent studies suggest that soil microbial communities may mediate the impacts of resource availability on plant performance, yet little is known about the net effect of conspecific soil microorganisms for tree seedling light responses. Here we examined the interactive effects of light availability and presence of conspecific soil microorganisms on tree seedling growth, morphology and nutrient content for two congeneric tropical tree species. The two Bauhinia tree species with contrasting shade tolerance were grown in sterilized or unsterilized soil medium, under either high (50%) or low (10%) light conditions in a greenhouse experiment. Plant light responses and soil feedback effects were determined after 12 weeks. Results showed that the light-demanding tree species was generally more responsive to both light and soil microbes compared with its shade-tolerant congener. Presence of soil microbes enhanced plant growth and biomass responses to increased light availability for the light-demanding species alone, driven by positive soil feedback effects in high light. Six plant traits (leaf mass fraction, stem mass fraction, specific stem length, leaf phosphorus concentration, leaf nitrogen: phosphorus ratio and root nitrogen: phosphorus ratio) showed significant interactive effects between light and soil treatment. Observed changes to leaf biomass allocation in response to light in the presence of conspecific soil microorganisms were consistent with optimality theory and adjustments to maximize resource acquisition under different light conditions. In addition, presence of soil microbes decreased the average plasticity of plant nutrient content and stoichiometry in response to light for the light-demanding Bauhinia species. Together these results highlight the importance of conspecific soil microbes for plant-light relations, with implications for plant-plant interactions and species coexistence

Appendix 1. PRISMA work flow dragram;Appendix 2. Literature list;Appendix 3. Dataset for meta-analysis;Appendix 4. Meta-analysis of other covariates;Appendix 5. Publication bias from Species richness alters spatial nutrient heterogeneity effects on above-ground plant biomass

to show how studies were searched and selected;A list of literature selected for meta-analysis;Dataset extracted for the meta-analysis;meta-analysis for other covariates ;details on analysis of publication bia

Drought soil legacy alters drivers of plant diversity-productivity relationships in oldfield systems

International audienceEcosystem functions are threatened by both recurrent droughts and declines in biodiversity at a global scale, but the drought dependency of diversity-productivity relationships remains poorly understood. Here, we use a two-phase mesocosm experiment with simulated drought and model oldfield communities (360 experimental mesocosms/plant communities) to examine drought-induced changes in soil microbial communities along a plant species richness gradient and to assess interactions between past drought (soil legacies) and subsequent drought on plant diversity-productivity relationships. We show that (i) drought decreases bacterial and fungal richness and modifies relationships between plant species richness and microbial groups; (ii) drought soil legacy increases net biodiversity effects, but responses of net biodiversity effects to plant species richness are unaffected; and (iii) linkages between plant species richness and complementarity/selection effects vary depending on past and subsequent drought. These results provide mechanistic insight into biodiversity-productivity relationships in a changing environment, with implications for the stability of ecosystem function under climate change

Arbuscular mycorrhizal trees influence the latitudinal beta-diversity gradient of tree communities in forests worldwide.

Arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) associations are critical for host-tree performance. However, how mycorrhizal associations correlate with the latitudinal tree beta-diversity remains untested. Using a global dataset of 45 forest plots representing 2,804,270 trees across 3840 species, we test how AM and EcM trees contribute to total beta-diversity and its components (turnover and nestedness) of all trees. We find AM rather than EcM trees predominantly contribute to decreasing total beta-diversity and turnover and increasing nestedness with increasing latitude, probably because wide distributions of EcM trees do not generate strong compositional differences among localities. Environmental variables, especially temperature and precipitation, are strongly correlated with beta-diversity patterns for both AM trees and all trees rather than EcM trees. Results support our hypotheses that latitudinal beta-diversity patterns and environmental effects on these patterns are highly dependent on mycorrhizal types. Our findings highlight the importance of AM-dominated forests for conserving global forest biodiversity

Arbuscular mycorrhizal trees influence the latitudinal beta-diversity gradient of tree communities in forests worldwide.

Arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) associations are critical for host-tree performance. However, how mycorrhizal associations correlate with the latitudinal tree beta-diversity remains untested. Using a global dataset of 45 forest plots representing 2,804,270 trees across 3840 species, we test how AM and EcM trees contribute to total beta-diversity and its components (turnover and nestedness) of all trees. We find AM rather than EcM trees predominantly contribute to decreasing total beta-diversity and turnover and increasing nestedness with increasing latitude, probably because wide distributions of EcM trees do not generate strong compositional differences among localities. Environmental variables, especially temperature and precipitation, are strongly correlated with beta-diversity patterns for both AM trees and all trees rather than EcM trees. Results support our hypotheses that latitudinal beta-diversity patterns and environmental effects on these patterns are highly dependent on mycorrhizal types. Our findings highlight the importance of AM-dominated forests for conserving global forest biodiversity