ASSESSING THE VALUE OF POTENTIAL "NATIVE WINNERS" FOR RESTORATION OF CHEATGRASS-INVADED HABITAT

Native plants that are able to persist and reproduce in highly disturbed habitats (i.e., "native winners") may be useful to include in seed mixes when restoring similarly disturbed habitat. Establishing whether these plants produce viable seeds that germinate to a high degree under appropriate conditions is a first step to determining their utility as restoration species. We identified 10 potential native winners at sites degraded by cheatgrass (Bromus tectorum), an invasive annual grass ubiquitous in the Colorado Plateau. We assessed seed viability for each species to determine its potential to reproduce within a cheatgrass-invaded site, and conducted a series of germination and competition experiments to test how effective these species may be when restoring habitat invaded by cheatgrass. All species produced viable seed (ranging from 56% to 100% viability), and the seeds of many species had high germination under a range of fall conditions without cold stratification, which is thought to increase establishment potential in cheatgrass-dominated habitats. We selected the 5 species with the highest germination and conducted a greenhouse competition study to determine their response to cheatgrass presence. The growth of all 5 forb species was suppressed by cheatgrass. However results from germination and competition trials suggest that several species, in particular Acmispon humistratus, Cryptantha fendleri, and Machaeranthera tanacetifolia, may be beneficial for restoration of cheatgrass-invaded sites. These 3 species have higher percent germination (78%-100%) and germination tolerance (0.42-0.63), and were suppressed less by cheatgrass (relative interaction index of negative 0.28-0.49) than a commonly seeded restoration species, Penstemon palmeri. Acmispon humistratus and M. tanacetifolia, in particular, are also desirable candidates for use in restoration because of the ecosystem services they provide. In general, natives that grow, reproduce, and tolerate competition in degraded habitats are potential native winners and worthwhile candidates for use in restoration of similarly degraded sites.