|Wilsey, Brian - IOWA STATE UNIVERSITY|
Submitted to: Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 22, 2004
Publication Date: May 19, 2004
Citation: Wilsey, B.J., Polley, H.W. 2004. Realistically low species evenness does not alter grassland species-richness-productivity relationships. Ecology. 85(10):2693-2700. Interpretive Summary: Humans are reducing the number of plant species that are present in many biological systems and are creating greater disparity in the abundances of remaining plants with some species becoming very abundant and others becoming rare. Recent studies have shown that the loss of plant species may reduce plant productivity in grasslands. Whether the increasing disparity in species abundances also is affecting the capacity of grasslands to meet human needs is not known. To determine effects of both species number and species abundances on grasslands, we experimentally varied the number of plant species and their abundances in small plots. Both plant biomass and net uptake of carbon by plants declined when the number of species was reduced. Effects of species number on plant production were the same, however, whether species were equally abundant or whether some were very abundant and others were rare. Over the two years of this experiment, some species were lost or became extinct from plots. Importantly, extinctions were greater in plots in which some species were very abundant and others were rare than in plots in which all species were equally abundant. Our results indicate that the productivity of grasslands may decline as plant species are lost independently of how abundances are distributed among species. However, activities that increase the disparity in abundances among plants may accelerate species loss and the accompanying decline in grassland productivity.