Atmospheric acidity and its impacts on atmospheric macronutrient deposition

Biological diversity and competition among species in ecosystems are sensitive to changes in macronutrient supply and pollution exposure. Human activity is intensively and extensively altering macronutrient cycles from a regional to a global scale with emission rates that are greater or comparable to natural ones. Moreover, anthropogenic pollution exposes ecosystems to additional nutrients and stresses, which affect their stability and productivity. These processes can have a strong impact on local ecosystems where atmospheric transport plays a central role in spreading macronutrients and pollutants. Within this project, we propose to characterise the atmospheric deposition fluxes of bioavailable nitrogen (N), phosphorous (P) and pollutants at the Bois-Chamblard site and their potential impact on plants and soil quality.

The exposure of the site to macronutrients has been determined by monitoring the total N and P in gas, rain water and airborne particles. To evaluate the effect of atmospheric deposition on plant and soil as a nutrient path, we settled a mesocosm experiment using 18 transparent boxes in controlled conditions to prevent and quantify atmospheric nutrients deposition. Both plants (oat) and bare soil were placed inside each box. Both plants and bare soil boxes were purged with air continuously filtered from and watered with pure water only, or exposed to unfiltered air and rainwater. With this approach we compared the plants and soil activity with and without the influence of nutrients from the deposition of air pollutants. Upon plant harvesting, we compared several parameters for all type of experiments including plants biomass productivity, stoichiometry, and chlorophyll content, soil stoichiometry, enzymatic activity, and microbial population. Standard methodologies and techniques developed “ad-hoc” in our group are applied altogether for the first time to have a comprehensive understanding of the impact of atmospheric deposition to soil-plant interaction. The research has been conducted in collaboration with Prof. A. Buttler from ECOS lab (EPFL), and Prof. C. Grossiord from PERL lab (WSL/EPFL).