THE ROLE OF BIODIVERSITY ON ECOSYSTEM FUNCTIONING: A REMOVAL EXPERIMENT IN THE PATAGONIAN STEPPE, ARGENTINA The Role of Biodiversity on Ecosystem Functioning: A removal experiment in the Patagonian steppe, Argentina

P. FLOMBAUM; O. E. SALA

Portland, Oregon, EEUU

Congreso; 89th Annual Meeting of the Ecological Society of America; 2004

Ecological Society of America

We know that biodiversity would be drastically reduced in the following years, but we are uncertain about the effects of losing these species on ecosystem functioning. We tested the biodiversity-productivity hypothesis that states that increasing species richness results in increasing ecosystem functioning. We created a richness gradient by removing species in the Patagonian steppe. The Patagonian steppe is an ideal model ecosystem because of the low natural diversity with 6 dominant species that account for 96% of aboveground net primary production (ANPP). In 84 (5x5m) plots that initially all contained the 6 dominant species, we removed target individuals and left 1, 2, 4 and 6 species with all possible assemblages replicated. We ensured at the starting point, that all plots had the same vegetation cover but different species number by removing portions of each individual.We found a strong biodiversity effect and that ANPP increased linearly with species diversity (F1,82=41.3; p<0.001). We calculated the relative importance of niche complementarity and sampling effect, and we found that niche complementarity accounted for most of the biodiversity effect and that it increased with increasing diversity. Ecosystem functioning increased with species richness because different species use different resources or because they established positive interactions among them.The slope of the biodiversity-productivity relationship in our experiment was much steeper than previously reported. Previous experiments used communities, which started from seeds, and consequently had short period of time to develop positive interactions among individuals. Our removal approach used individuals that had been established in the same location for long periods of time, and therefore had a chance to develop positive interactions. Our results indicate that the biodiversity effect in natural ecosystems may be stronger than previously thought based on studies with artificial communities.