Resource heterogeneity and grassland diversity: the importance of clonality and scale.
Reynolds, Heather*,1, Mittelbach, Gary2, Darcy-Hall, Tara1, Houseman, Greg2, Gross, Katherine2, 1 Indiana University, Bloomington, IN2 Michigan State University, East Lansing, MI
ABSTRACT- Coexistence theory predicts that greater heterogeneity of resources or other fitness-constraining environmental factors will promote species diversity, but this classic mechanism of coexistence has not been well tested in the field. Here we present results from the fourth year of a long-term experiment designed to test the heterogeneity-diversity hypothesis in low productivity prairie grassland where we directly manipulated the spatial heterogeneity of a limiting soil nutrient (nitrogen). In addition to unfertilized controls, we created heterogeneous and homogeneous nutrient enrichment treatments using fertilizer applied to field plots in a uniform or patchy manner. In contrast to our predictions, we found that spatially heterogeneous soil nutrient supply did not promote increased species richness or greater species sorting relative to a uniform supply of soil nutrients. Instead, nutrient enrichment depressed plant species richness (especially at small spatial scales) and increased the abundance of aggressively spreading clonal species. Our results suggest that clonal species may strongly constrain how plant diversity responds to resource heterogeneity and point to the importance of judging the scale of resource heterogeneity in relation to the foraging footprint of the plant species involved.
Key words: heterogeneity and diversity, prairie grassland, restoration
All materials copyright The Ecological Society of America (ESA), and may not be used without written permission.