The role of competition and seed production environment on the success of two perennial grass species in a roadside restoration

Authors: Espeland, Erin; RICHARDSON, LAURIE - Department Of Fish And Wildlife

Submitted to: Ecological Restoration
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/28/2015
Publication Date: 11/3/2015
Publication URL: http://handle.nal.usda.gov/10113/61585
Citation: Espeland, E.K., Richardson, L. 2015. The role of competition and seed production environment on the success of two perennial grass species in a roadside restoration. Ecological Restoration. 33(3):282-288.

Interpretive Summary: Because adaptation of plants to their environment is common, local seed collections are often used for restoration. But, how local is local? When we collect seeds from natural areas and subject them to agricultural environments during seed increase, we expose these seed populations to forces of natural and assisted selection, potentially changing the genetic makeup of the populations that are then seeded into restorations. We don’t know how a single generation of agronomic production can change seed success in restoration, either by increasing it or by somehow maladapting seeds for use in natural environments. In this study, we compare plants grown from wild-collected and agronomically-grown seeds of perennial grasses, originally sampled from the same wild populations. We asked if plant establishment and growth differed between seed sources (agronomically-grown or wild-collected). We also asked if simultaneously sowing annual forbs with the perennial grass populations affected perennial grass establishment and growth. By the second growing season, there were no differences in grass abundance among our treatments (with or without annual forbs, agronomically-grown or wild-collected). Competition from other plants rarely suppressed the growth the native perennial grass species, and facilitation from neighboring forbs increased perennial grass productivity in the second growing season. Our study supports the widespread utilization of plant materials centers for large-scale seed production and also supports the diversification of restoration plantings.

Technical Abstract: When large-scale restorations are undertaken using local genotypes, wild-collected sources often undergo a generation in an agronomic environment for seed increase. We have 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 seeds, 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; competition at later stages was assessed by cataloging plant neighbors. 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, and facilitation from neighboring forbs increased productivity of both species in the second growing season.