North American tallgrass prairie ecosystems have been reduced to a fraction of their pre-European settlement ranges. Foundation grasses like Andropogon gerardii (big bluestem or BBS) are vital for prairie restorations. Because foundation species genes can be linked to community and ecosystem patterns and processes, restoration success could be driven, at least in part, by foundation genetic variation. Here, we exploit unanticipated consequences of a sod transfer experiment in an effort to better understand how BBS genetic variation alters or is altered by below-ground interactions in ways that affect restoration success. We are using genetic markers (AFLP) to test whether an unpredicted increase in the relative abundance of BBS altered genetic structure at a restoration site. The restoration proceeded by cutting sod from a prairie remnant (Site 1) threatened by development in Northwest Arkansas and moving it to another, nearby remnant site (Site 2). Sod was transferred to a heavily disturbed agricultural plot (Site 3) within Site 2 and monitored for regeneration and changes in species richness and abundance. Changes in BBS cover prompted us to initiate a molecular genetic study to characterize standing genetic variation within sites, structure among sites, and to document changes in variation at Site 3.
Results/Conclusions
BBS abundance was unusually low at Site 1, accounting for only ~10% cover. However, following sod transfer, abundance increased to 50% cover at the expense of other species. We have collected representative samples from all three sites in order to assess how genetic variation has changed in the sod transfer plot vs. the two native sites. We are currently analyzing DNA samples in order to determine the extent to which sexual vs. asexual reproduction is altering genetic variation at site 3 compared with its source (site 1). Grasslands are analogous to the “tip-of-the-iceberg” in that most of the biomass is underground. As such, many if not most ecologically significant interactions also occur underground. In our study, the transfer of a relatively thin layer of prairie to a site with intense, decades-scale disturbance almost certainly influenced the shift in BBS abundance. If so, we have a unique opportunity to look for links between foundation species genetics and interactions with soil communities that have apparently favored BBS, and, potentially, specific BBS genotypes. Our project could therefore prove useful for understanding how below-ground disturbances act to alter conservation or restoration efforts that involve foundation prairie plants and their associated communities and ecosystems.