Species evenness affects ecosystem processes in situ via diversity in the adaptive strategies of dominant species

Community biomass production reflects species evenness (relative abundance), suggesting that particular adaptive/survival strategies contribute disproportionately to ecosystem processes. We hypothesized that diversity in the strategies of dominant species would be a better predictor of biomass production than species diversity per se. We compared species diversity, strategy diversity, peak biomass, soil and leaf nutrient status, and leaf area index (LAI) in situ for related sub-alpine plant communities differing only in the intensity of cattle grazing and manuring; with identical climatic exposure, slope, aspect and parent material. Greater total biomass was associated with greater strategy richness and evenness and, to a lesser extent, species evenness-but species richness and aboveground biomass were not significantly different. Diversity in the adaptive strategies of dominant species allowed more effective deployment of canopy biomass (greater LAI), providing superior photosynthetic nutrient use efficiencies and greater total biomass despite lower nutrient status. This was reflected in species evenness, but not species richness.