Impact of nutrient availability on the diversity, function and functioning of forest soil bacterial communities: Insights on soil succession at the experimental forest site at Montiers-sur-Saulx
PI : Stéphane Uroz (UMR – Interactions Arbres/Micro-organismes – IAM et UR Biogéochimie des écosystèmes forestiers – BEF)
Co-applicants : Dynamic, EEF, ENSTIB/LERMAB
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Context — Forest ecosystems today are facing intensified exploitation of wood as a resource. As such, maintaining the capacity of the soil for production and the quality of the environment has become a central issue in sustainable forest management. Developing forest ecosystems on non-fertilized and nutrient-poor soils renders these ecosystems sensitive to nutritive perturbations. In this context, pertinent questions would be to understand how nutrient cycles are maintained in such forest soils, how trees are able to collect the nutrients required for growth, and lastly, where do these nutrients come from. Apart from the recycling of elements contained in the organic and atmospheric deposition, soil minerals are an essential source of nutrients. The process of solubilization of these minerals is therefore essential as the nutrient cations trapped in minerals remain inaccessible to the roots of the trees.
Objectives — To determine through an interdisciplinary approach how soil nutrient availability impacts the functional and taxonomic structuration of the bacterial communities in different reactive interfaces (rhizosphere, mineralosphere, soil, phyllosphere..).
Approach — To address such questions, the soil toposequence of the experimental site at Montiers-sur-Saulx, characterization by the same land cover dominated by Fagus sylvatica and 3 soil types with contrasting soil properties was used to combine soil sciences, organic chemistry, microbial ecology, environmental microbiology, and metagenomics in situ or using microcosms experiments allowing manipulation of the nutrient availability.
Key results —
The first year of the INABACT project generated several key results :
- Soil chemical analyses confirmed the gradient of properties of the Montiers soil toposequence
- Organic chemistry allowed to the identification of the main soluble carbohydrates (ie glucose)
- Culture-dependent approach revealed an enrichment of effective mineral weathering bacteria in the soil characterized by the lower nutrient availability level and more acidic pH
- Culture-independent approach revealed a strong differentiation of the bacterial communities along the soil toposequence in term of taxonomy based on 16S rRNA pyrosequencing, not correlated to the functional diversity analysed using DNA microarray.
- The micro-scale approach (micro-aggregates of soil) allowed to the generation of bacterial collections, which are currently at the taxonomic and functional characterization stage.
- Preliminary results on minerals incubated in forest soil during 2.5 years revealed a differentiation of the bacterial and fungal communities according to the mineral type.
The first results obtained in the frame of the INABACT project show that microbial communities are strongly shaped by their environment. Notably, we highlighted through both cultivation-dependent and -independent approaches that bacterial communities are strongly impacted by the trees (rhizosphere effect) and the soil type (soil effect). Our results obtained in situ or in microcosms suggest that Fagus sylvatica select specific communities according to the soils conditions.
Future perspectives — In the next coming years, research focused on deciphering the taxonomic and functional diversity will continue with a specific focus on the impact of nutrient availability. Analyses the functional potential of bacteria collected from the limestone/root interface are in progress and should permit to better appreciate the role of bacterial communities in nutrient cycling and tree nutrition in these specific calcareous soils. A microcosm approach will be developed to determine if nutrient amendment impacts the structure and diversity of soil bacterial communities. Altogether, the data generated in the frame of this project will allow for a greater understanding of the complex relationships that exist between soil fertility, tree nutrition and microbial functioning. All data which has been generated and analysed are currently at the publication preparation stage.
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Publications:
Jeanbille, M., Buée, M., Bach, C., Cébron, A., Frey-Klett, P, Turpault, M-P., Uroz, S. Soil parameters drive the structure, diversity and functions of the bacterial communities across a temperate beech forest soil sequence. Microbial Ecology. In press.
Conferences:
– Colloque de l’Association française d’écologie microbienne (AFEM), (Anglet, France) 3-6 novembre 2015. Impact of nutrient availability on the structure of the forest bacterial communities : Insights from the Montiers soil succession O. Nicolitch, Y. Colin, M-P. Turpault, S. Uroz (Oral).
– Summer school ‘Function of microbial communities in soils: biotic interactions’ (Neuherberg, Germany) 31th august-11th september 2015. Mineral weathering in forest soils: focus on the bacterial communities. Uroz et al. (Oral); Impact of nutrient availability on the structure of the forest bacterial communities : Insights from the Montiers soil succession O. Nicolitch, Y. Colin, M-P. Turpault, S. Uroz (Poster)
-Colloque ‘Expérimentation sur le site de Montiers’ (Champenoux, France) 20 mars 2015. Relation entre le type de sol et la structure taxonomique et fonctionnelle des communautés bactériennes, S. Uroz et al. (Oral)
– First Global Soil Biodiversity Conference (Dijon, France) 2-5 décembre 2014. Impact of soil type on the structure of the microbial communities: Insights from the Montiers-sur-Saulx soil succession. Nicolitch, O., Jeanbille, M., Buée M., Colin Y., Turpault M-P., Frey-Klett P. and Uroz S. (Poster)
