A SToichiometric ECosystem model to link biodiversity and ecosystem functioning in agro-ecosystems – ASTEC

The biodiversity crisis that we are currently experiencing requires that we develop operational tools to assess the impact of human activities on biodiversity and ecosystem functioning. Alarming global biodiversity projections do exist for the coming century, as influenced by global warming and land use changes. In contrast, there is still no operational tool available to conduct biodiversity scenarios at the landscape scale at which alternative developmental pathways can be imagined. The ambition of the ASTEC project is to fill this gap by developing an operational simulation tool of landscape biodiversity dynamics, taking into account the human impacts linked to agricultural and sylvicultural practices, but also linked to urbanization. European landscapes, and French ones in particular, are for their vast majority occupied by strongly human altered agro-ecosystems. In such systems, biodiversity conservation must necessarily be thought with regards to agricultural and sylvicultural production imperatives. There is thus a strong stake for developing agro-ecological practices that greatly benefit from ecosystem functioning. The second ambition of the project is thus to model a mechanistic link between biodiversity dynamics and ecosystem functioning dynamics, mobilizing the concepts of ecological stoichiometry. This ecological theory considers the nutritional needs of organisms and thereby bridges nutrient cycles and food web dynamics in ecosystems. It will enable us to enlighten how modification of nutrient cycles (carbon, nitrogen and phosphorus) by human activities impact the functioning of food webs in a given plot, and how these effects of nutritional constraints diffuse in agricultural landscapes between different habitats. To this end, we will model the dynamics of major functional groups of an agro-ecosystem (plants, invertebrates, reptiles, mammals, birds…) and of the associated nutrients (carbon, nitrogen and phosphorus), expliciting the processes of production and consumption of resources, demographic and dispersal processes, nutrient recycling processes, and the effect of human practices on these various processes. This modelling will be split in two main tasks: task 1 at the plot scale with an aspatial model and task 2 at the landscape scale with a spatially-explicit model building on the one of task 1. Afterwards, we will apply the landscape-scale model to a concrete case study, analysing different scenarios of land use changes (and associated human practices) by 2050, in the context of the “Territorial Food Project of the Clermont-Ferrand area” (task 3). This work will build on recent syntheses on stoichiometric constraints in a wide range of organisms that now make this project feasible.