NP PROJECT

As a result, atmospheric reactive N deposition has increased globally from 32 Mtones N yr-1 in 1860 to ~ 112-116 Mtones N yr-1 nowadays. Current projections expect a further enhancement that will raise the total global annual N deposition to ~ twofold the current levels by 2050. Human activity tends to fertilize the biosphere with P, but at a smaller rate than the increases in the availabilities of C and N. The Global P inputs in fetilizers have remained more or less constant since 1989.The resulting imminent change in the stoichiometry of available elements will have no equivalent in the Earth’s history and will bear profound, yet, unknown consequences for life and the Earth System. The ongoing shifts in C:N:P balances in ecosystems will necessarily affect the structure, function and diversity of the Earth system. A few studies have observed that changes in ecosystem structure and function have begun to occur, mainly in Europe and North-America. However, in contrast to the global tendency to an enhancement of the N:P ratio, P is polluting some agricultural areas where it decreases the N:P ratio of waters in soil. This occurs particularly in areas with intense pasture and animal slurry use for land fertilization. While N is more mobile and consequently tends to leach easily from crop soils to water, P inputs from fertilizers tend to remain and accumulate in crop soils. 

Our project NP aims to study the effects of N:P imbalances on terrestrial organisms, communitites and ecosystems, both on their structure and functioning. NP will thereafter focus on the flow-on consequences for CO2 and BVOC (biogenic volatile organic compounds) exchange of terrestrial ecosystems and finally for the whole Earth system. We will use updated techniques at the molecular, individual, community and ecosystem level, including metabolomics, gas exchange and hyperspectral remote sensing techniques to assess NP changes and their impacts in space and time. We will use data mining, observational and experimental studies to detect the hypothesized key shifts in structure and function of organisms, communities and ecosystems. Subsequentially, by implementing the results obtained into Earth system models and in colaboration with other international groups we will then calculate the effects of N:P imbalances for the global carbon budget and climate. In parallel to the measurements of CO2 exchange under different N:P ratios, we will also measure BVOC exhange since BVOCS emissions depend on nutrient availability and may have large ecological and environmental impacts. Also in parallel, we will use hiperespectral spectroradiometers in UAV (unmanned air vehicles) and satelites to assess the impacts in our experimental plots and in natural gradients to develop tools to improve such assessment, including the asessment of CO2 and BVOCs exchanges..