Resource competition and community response to fertilization: the outcome depends on spatial strategies
Decreases in plant species richness and shifts in community structure following fertilization are usually attributed to increasing light limitation. However, there is increasing evidence that light limitation alone does not account for all of the observed effects of fertilization on plant communities. We present a model of competition for a single, spatially heterogeneous resource that shows fertility-mediated changes in community structure without light competition. This model predicts that in a low-productivity spatially heterogeneous habitat, species that interact with the resource environment over small spatial scales may exclude species that experience the environment at larger spatial scales, even when the latter species are better resource competitors in a uniform environment (have a lower R*). Increasing overall habitat fertility under these conditions minimizes the effects of spatial heterogeneity on the species that forage at a larger spatial scale, resulting in changes in species dominance and the potential for species coexistence. This analysis suggests that considering differences in the spatial scales at which species interact with environmental heterogeneity may help explain observed changes in community structure following fertilization.
KeywordsClonal plants Fertilization Light limitation Resource competition Spatial heterogeneity Coexistence Community structure
This work was supported by grants from the National Science Foundation (DEB-0235699), the A.W. Mellon Foundation, and Michigan State University. We are grateful to Jim Grace and Tim Dickson for helpful comments on the manuscript and to the Michigan Department of Natural Resources staff at the Allegan State Game Area for allowing us to conduct field experiments at the site. This is KBS contribution number 1727.
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