VERTIcal stratification and functioning of the funGal and bactErial microbial communities in the canopy of a tropical rainforest


Labex CEBA – 2018 (1 year)



Scientific Partnership

  • BIOGECO - Corinne VACHER & Tania FORT (PhD)
  • ENS - Lucie ZINGER

For UMR EcoFog :

Presentation of the project

Leaves are colonized by a huge diversity of microbial species named the phyllosphere microbial communities (hereafter PMCs). Early studies on microorganisms on tropical trees leaves suggested that PMCs have the ability to fix atmospheric nitrogen and may provide nitrogen to the plant. Since then, the significant influence of PMCs on the functioning of tropical forests - pathogen mitigation, plant/insect interactions or seedling survival - have been demonstrated. Some of these microorganisms become saprotrophs after the onset of the senescence of the leaf. A current challenge is to quantify the positive, neutral and negative effects of foliar microorganisms on the physiology of tropical trees, and integrate these findings to assess the impact of PMCs on functioning of forest canopies. The variations in the chemical composition of the tropical trees leaves associated with the strong light and water gradients create a vertical stratification in PMCs structure and composition. However, no quantitative fine- scale studies exist linking the structure and function of PMCs to within-canopy variation in leaf microclimate and leaf functional traits. In neotropical rainforest, N-fixing trees species play a major role in the N-cycle through their symbiotic interactions with soils diazotrophs, but the distribution of N-fixing bacterial communities in the canopy of tropical forests or the differences of their communities between nodulating and non-nodulating tree species has not been studied so far. Combining functional plant traits, accurate microenvironmental data and metabarcoding, the VERTIGE project aims at exploring the PMCs in tropical rainforest trees, particularly looking at the influence of the light and humidity gradients associated to foliar characteristics shape PMCs. We will test the hypothesis that N-fixing epiphytic bacterial communities are more diverse on top of the canopy where light is non limiting than in the understorey and whether they are richer in non-nodulating tree species. On the opposite, saprotrophic fungal endophytic communities might be more diverse in the understorey. This innovative and original approach will give new insights into the understanding of how microbial diversity is related to host function, both considering PMCs as a potential functional trait or how they mediate other plant traits.

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