Effects of aboveground biodiversity on belowground characteristics in natural ecosystems: evidence from Patagonian forests

AUSTIN A.T., L. VIVANCO, A. FERNÁNDEZ-SOUTO, M. GONZÁLEZ-POLO, A. GONZÁLEZ-ARZAC, P. I. ARAUJO Y O. E SALA

Portland, Oregon, USA

Congreso; Annual meeting of the Ecological Society of America; 2004

@ Interest in understanding effects of biodiversity on ecosystem functioning has increased markedly in the last two decades, although the vast majority of experiments have been conducted using artificially constructed communities with short-lived species and on relatively short time scales. Challenges of spatial and temporal scale and confounding ecological factors have hindered the exploration of biodiversity effects in natural ecosystems with long-lived species, and in particular, forests. We examined the effect of aboveground diversity on belowground characteristics within a mosaic of mixed old-growth forest in temperate South America (40‹08ŒS, 71‹30ŒW), where such potential confounding factors such as climate, soil age and origin, and slope were controlled and held constant. We chose the canopy intersection of three trees as our sample area, tree triangles of varying diversity (three treatments of a single species, Nothofagus dombeyi, N. nervosa, and N. obliqua, and a single combination of the three Nothofagus species) to restrict the effective area of the impact of aboveground diversity on belowground characteristics. Analysis of litter layer composition demonstrated significant differences in the proportion of litter contributing to the detritus (P<0.05) with high percentages (>70%) of total litter in the single species triangles coming from that species. Soil C:N ratios differed significantly among tree triangle treatments (P<0.001), with the highest C:N ratios (20) in N. dombeyi triangles and the lowest in N. nervosa (14) triangles. Belowground communities demonstrated significant differences among tree triangle treatments, with lower overall abundance of mesofauna (P=0.02) and fewer orbatid mites in N. dombeyi triangles (P<0.05). While the extrapolation of changes in belowground characteristics to changes in biogeochemical cycles has yet to be demonstrated in this ecosystem, this evidence suggests that aboveground diversity does exert a control on belowground communities and soil characteristics.