Species richness increases the resilience of wetland plant communities in a tropical floodplain

In the last two decades, the relationship between diversity and stability/ecosystem functioning has been widely discussed and has become a central issue in ecology. Here, we assessed the relationship between wetland plant diversity and community resilience after a disturbance. Our study area was located in the Upper Parana River floodplain (Brazil). An experiment was carried out in situ (18 1m x 1m plots with richness varying from 1 to 18 species). In each plot, we recorded the number of species, total per cent vegetation cover and per cent age cover of each species. The above-ground biomass of wetland plants was removed, simulating a disturbance by animal trampling or an extreme flood. The recovery of vegetation was monitored over 3 months. According to a linear regression, the recovery of wetland plants was positively correlated with diversity. Comparisons with plots containing monocultures of one of the dominant species (Polygonum stelligerum) suggested that this species did not overyield in mixed cultures. Thus, our experiments indicate that the higher resilience in richer plots after a disturbance is mainly due to the fact that species have different resource use requirements (complementarity effect) and not due to the presence of a single, more productive species. Our experiment carried out in a more real condition (in situ) showed that biodiversity is important to wetland functioning and stability, paralleling the results obtained in laboratory and mesocosms experiments. These results also suggest that the loss of plant diversity in our study area could compromise community recovery following strong disturbances.