The current loss and alteration in global biodiversity have stimulated studies with the objective of understanding the impact of biodiversity on ecosystem functions. A pattern evidenced by these studies is that biodiversity positively affects ecosystem function, but with a less pronounced effect as diversity reaches higher values. Currently, one of the gaps is to understand the mechanisms behind this relationship between biodiversity and ecosystem function. One of the proposed mechanisms is facilitation between plants, defined as positive ecological interaction, in which at least one of the organisms involved is benefited. In this project, we will test a theoretical model that suggests facilitation by increasing soil fertility as an explanatory mechanism for the positive relationship between species richness and primary productivity, in communities with leguminous and non-leguminous plants. Our hypothesis is that the relationship between diversity and primary productivity is positively affected by the increase in the proportion of legumes, so that productivity is higher with more legumes regardless of the level of richness and that the effect of richness saturates faster in communities with more legumes. We will test our hypothesis with a field experiment in which we will establish plant communities composed of six plants for agricultural use and fast growth, in plots of 1 m2. To test the effect of legume richness and proportion respectively, the plots will have combinations of three levels of richness (1, 3, or 6 species) and two levels of legume proportion: high and low. For each treatment combination, we will have 5 replicates, totaling 30 plots. We will estimate the effect of the proportion of legumes and species richness on the primary productivity of the community by measuring the total biomass of each plot, after three months of planting. We expect the effect of the proportion of legumes to be greater in the poorest communities, with one or three species, than in the richest communities, with six species.
News published in Agência FAPESP Newsletter about the scholarship: