The effects of the presence of clonal growth form and soil resource heterogeneity on a sand prairie community

Background/Question/Methods

Heterogeneity in soil resources is predicted to facilitate coexistence between plant species and increase plot level species diversity.  However, clonal plant species have the capacity to integrate over heterogeneous resource patches, potentially muting the facilitation of species coexistence by soil resource heterogeneity.  To investigate these dynamics, the presence of clonal plant species and soil nutrient heterogeneity were manipulated in a naturally occurring sand prairie in Michigan.  Experimental plots in a repeated block design were seeded on cleared ground with 34 native unitary (non-clonal) species in the spring of 2004.  Half of the plots were also seeded with 8 clonal species, while clonal species were excluded from the other half by hand clipping.  Slow release fertilizer was added to generate the desired variation in soil resource heterogeneity.
Results/Conclusions

After two years of growth the unitary community exhibited significantly reduced biomass in the presence of clonal species.  In plots with both clonal and unitary species, only the clonal species exhibited increased biomass due to fertilization.  Unitary species richness decreased with nutrient enrichment in the presence of clonal species, but not when clonals were excluded.  This suggests that as clonal species biomass increases due to fertilization, it has a negative impact on the diversity of unitary species.  This research indicates both that a clonal growth form may allow plants to respond well to patchy habitats, and that this response can decrease the diversity of unitary communities.