Nutrient enrichment and local competition influence the evolution of plant mineralization strategy: a modelling approach
Résumé
1. It is important to study how evolution impacts on plant functional traits and to determine how this subsequently determines ecosystem functioning. We tackle this general issue by studying the evolution of plant strategies that affect mineralization through the chemical quality of their own litter and their position on the leaf economic spectrum. This spectrum allows us to classify all plants on single axis ranging from resource-acquisitive to resource-conservative strategies. 2. We build a spatially explicit and individual-based simulation model: individual plants grow in the cells of a lattice and the limiting nutrient is recycled locally in these cells. Individual plants may die and produce seeds that are dispersed. Mutants with different mineralization strategies appear stochastically. A trade-off is implemented between the rate of nutrient loss from plants and litter mineralization. 3. In the spatial-explicit model, plant capacity to increase mineralization evolves and reaches an evolutionary equilibrium in most cases. The evolved mineralization decreases with plant longevity, seed dispersal efficiency, spatial homogenization of mineral nutrient availability and inputs of mineral nutrient to the ecosystem. 4. The evolved mineralization strategies neither maximize plant biomass, nor minimize the availability of mineral nutrient or the stock of dead organic matter. The evolutionary and ecological impacts of nutrient enrichment on the stock of organic matter are different. 5. Synthesis. Our results suggest that plant mineralization strategy may evolve provided that the mineral resource is not fully shared by all individuals. Such an evolution modifies soil capacity to store organic carbon thereby being relevant in the context of the current climate change and global nutrient enrichment. Indeed, our model shows that evolutionary feedbacks of plants to nutrient enrichment are likely to differ from purely ecological feedbacks.