COS 67-2 - Seed mix design does not effect restored tallgrass prairie community structure when accounting for edge effects and plant-consumer interactions.
Abstract: A central goal of ecosystem restoration is to produce diverse native plant communities. The decisions managers make, especially regarding seed mixes, can influence whether a restoration meets that goal. Specifically, changing the number of species in a seed mix (interspecific diversity), or the number of seed sources of each species (intraspecific diversity) can impact plant community composition. Interspecific and intraspecific diversity may also interact to affect the structure of a restored community by modifying the abundance of ecologically important dominant species. However, aspects of seed mix design have rarely been rigorously tested, especially at large spatial scales, so the effect of manipulating them at a restoration site together remains unknown. Moreover, given that the outcomes of restorations are highly variable, other factors known to influence plant communities including proximity to the edge and consumer (e.g., herbivore, granivore) pressure may play a larger role in shaping these communities than seed mix design. Understanding how strongly each of these factors influences community structure is crucial to inform the restoration of native plant communities. Given these knowledge gaps, I aim to understand the impacts of (1) seed mix inter- and intraspecific diversity, (2) fences that exclude consumers, and (3) edge effects on restored prairie communities. To address these questions, we conducted a prairie restoration experiment at Kellogg Biological station where interspecific and intraspecific seed mix diversity, distance from the edge, and consumer access were manipulated. We found that there was no effect of seeded intraspecific diversity on species diversity or composition, whereas sowing high interspecific diversity increased species richness by two species/m2. Additionally, one of three common non-sown community dominants (Elymus repens, a weedy exotic graminoid) was affected by our seed mix treatments: areas with higher inter- or intraspecific diversity had less Elymus repens, indicating reduced invasibility. Finally, excluding consumers and sowing near habitat edges both reduced sown richness. Together, these results indicate that edge proximity and consumer pressure shape community structure, whereas seed mix composition may be more influential at controlling individual nuisance species abundances.
