Doctoral candidate: Océane Nicolitch
University: Université de Lorraine, France
Contract duration: 2014-2017
Research Topic — Impact of nutrient availability on the structure and functioning of the forest soil bacterial communities capable of weathering minerals
Research team and supervising scientists —
Research teams : Ecogenomic Team, UMR 1136 Joint Research Unit for Tree/Microorganism Interactions (IAM) and UR 1138 Research Unit for Forest Ecosystem Biogeochemistry (BEF)
PhD supervisors : Stéphane Uroz and Marie-Pierre Turpault
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Context —
In nutrient-poor environments such as temperate forest ecosystems, nutritive cations are often inaccessible to tree roots. This limitaiton is further exacerbated due to the exportation of wood by the forestry industry, leading to further loss of nutrients. At the time of harvesting, these nutrients are not recycled during the process of organic matter degredation. Such an interruption in nutrient recycling can lead to potential nutritive deficiencies if no other nutritive sources are available. Consequently, maintaining production capacity levels in soils and the quality of the environment is a central issue for sustainable forest management. In this context, it is interesting to question how trees collect the nutritive cations necessary for their sustainable growth in such nutrient-poor ecosystems and to identify the sources of these inorganic nutrients.
Aside from contributions related to atmospheric deposition and the recycling of nutrients in dead roots and leaves, the soil minerals are the major source of nutrient cations available for the functioning of the ecosystem. The release of nutrients from these minerals (weathering processes) becomes a process crucial to the proper functioning of the ecosystem. But how does this mineral weathering operate? What are the relative contributions of abiotic and biotic reactions in this weathering process?
The current challenge lies in identifying: i) the microorganisms involved and their interactions, ii) their contribution to the nutrient cycling processes, particularly those related to mineral weathering and soil fertility, iii) the molecular mechanisms involved in mineral weathering and iv) the parameters regulating the structure of these microbial communities.
Objectives and specific questions to be addressed —
The main objectives of this project are to test the impact of availability of nutritive cations (Ca, K, Mg, and P) on the structure and functioning of the bacterial communities of forest soils capable of weathering minerals.
Scientific and socio-economic issues —
This project will aim to highlight and further our understanding of possible links between soil fertility, the structure of soil bacterial communities and the promotion of tree growth. This study also promises to identify the bioindicators which reflect soil quality.
Methodological approaches and expected results —
To address the key questions, our approach will be to combine methods used in microbiology (Pasteur and metagenomics) and soil sciences. Part of the project will be developed in the field on the forest experimental site located in Monriers-sur-Saulx using soil microcosms. These experiments will allow us to determine if trees select bacterial communities capable improving their nutritional state regardless of the soil condition and soil nutrient availability.
