Effects of biodiversity and environment on the ecosystem multifunctionality of a tropical forest

Abstract

Ecosystem multifunctionality (EM) results from the complexity of the interactions between biotic and environmental components. These interactions are expressed both at ecosystem function (EF) and ecosystem service (ES) levels. EM is positively associated with biodiversity, constituting a multilayered relationship between biodiversity-EF and biodiversity-ES. Understanding this relationship is a key issue to deal with the anthropogenic impacts on natural ecosystems. In this study, we tested the hypothesis that both biotic and environmental variables explain the EM and that biotic and environmental variables are drivers of different components of the ecosystem. We collected the data in 10 ha (10 plots of 1ha each) in the largest fragment of Atlantic Forest in Southern Brazil. We sampled data of six EF and ES indicators (above-ground biomass, flower productivity, hummingbird-plant interactions, litter decomposition, topsoil attributes, and watercourses), environmental data (canopy cover, steepness, and subsoil attributes) and biotic data (ants, anurans, birds, fishes, hymenopteran, juvenile trees, small mammals and trees). We used agglomerative cluster analysis to identify groups of ecosystem indicators (spatial, environmental and biotic drivers) and RDA and variation partitioning to test for their effects on EM. We sampled a total of 476 species (11,331 organisms) within the studied area. The EM was separated into three groups: flower productivity & soil; water flux & plant-hummingbird interaction; and above-ground biomass & decomposition. The ecosystem variables were 9% explained by steepness, 4% by the juvenile trees' community, and 16% by both variables. The EM groups and the drivers were positively or negatively related. The diversity of juvenile trees seems to be a key component for the local ecosystem functioning, and steepness, the main driver for productivity. Our findings suggest that EM and biodiversity are strongly interconnected, and changes in key elements could cause a chain of changes in the local ecosystem and in the biodiversity.