To test the hypothesis that the impacts of grazers on plant species richness reverse under contrasting nutrient richness, Proulx and Mazumder analyzed unpublished and published data from lake, stream, marine, grassland, and forest ecosystems. They analyzed data from 30 studies providing 44 comparisons of plant species richness under low vs. heavy grazing pressure in enriched or nutrient-rich and non-enriched or nutrient-poor ecosystems. Based on all of their comparisons, plant species richness decreases with high grazing in nutrient-poor ecosystems, while it increases with high grazing in nutrient-rich ecosystems. Although nutrient-rich ecosystems seemed to produce more variable responses to grazers than did nutrient-poor ecosystems, in rare cases high grazing produced a decline in species richness in nutrient-rich ecosystems. The authors suggest a limitation of available resources prevents regrowth of species after grazing, which may not be the case in nutrient-rich ecosystems. Their observation of a grazer reversal of plant species richness under contrasting nutrient richness may have important implications for management of species diversity.
Citations and enhanced abstracts for journals articles and documents focused on rangeland ecology and management. RSIS is a collaboration between Montana State University, University of Idaho, and University of Wyoming.