The Role of Competition and Seed Production Environment on the Success of Two Perennial Grass Species in a Roadside Restoration

When large-scale restorations are undertaken using local genotypes, wild-collected sources often undergo a generation in an agronomic environment for seed propagation. Currently, there is little information on how a single generation of agronomic production can alter seed success in restoration. In this study, we compare plants grown from wild-collected and agronomically-grown seed sources, originally sampled from the same wild populations. We asked if emergence and growth differed between seed sources (agronomically-grown or wild-collected) when initial levels of competition were manipulated in the first growing season by simultaneously sowing annual forbs and cataloging plant neighbors to assess competition at later stages. Our two study species, western wheatgrass (Pascopyrum smithii) and green needlegrass (Nassella viridula) did not exhibit a competitive response to annuals in the first growing season, and by the middle of the second growing season there was no effect of source environment on plant performance. Greater green needlegrass emergence from the agronomic source in the first year did not translate into more abundance or plant biomass by the middle of the second growing season. Competition was rarely important in suppressing the growth of these two native perennial grass species, but facilitation from neighboring forbs increased productivity of both species in the second growing season. Any maternal effects or selection imposed by the agronomic increase environment does not appear to affect seedling establishment and growth. Sowing annual forbs as part of restoration mixes may promote perennial grass growth as well as provide services to pollinators.