Germination timing and rate of locally collected western wheatgrass and smooth brome grass: the role of collection site and light sensitivity along a riparian corridor

Authors: Schantz, Merilynn; Espeland, Erin

Submitted to: Native Plants Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/10/2015
Publication Date: 4/1/2016
Publication URL: http://handle.nal.usda.gov/10113/62356
Citation: Schantz, M.C., Espeland, E.K. 2016. Germination timing and rate of locally collected western wheatgrass and smooth brome grass: the role of collection site and light sensitivity along a riparian corridor. Native Plant Journal. 17(1):28-37.

Interpretive Summary: Our rivers and waterways are being invaded by aggressive plant species like smooth brome grass. Smooth brome actively invades recently disturbed riparian areas by its high seed production and fast seedling establishment. Restoring native perennial grasses to these regions is challenging because continual disturbances from erosion and/or flooding decrease existing vegetation and increase the area for further plant invasions. Identifying growth traits of common native perennial grasses, like western wheatgrass, compared to smooth brome should provide managers necessary information on smooth brome invasion and restoration. In this study, we sought to identify how the germination timing and rates of smooth brome and western wheatgrass were affected by seed site location and light availability. Regardless of site or light dynamics, we found that smooth brome grass germinated two days earlier and at five-times higher rates than western wheatgrass. Sites that had high levels of human-caused disturbances also had high seedling germination rates for both smooth brome and western wheatgrass. In addition, when light was restricted for the first few growing days, seedling germination of both species were higher than when light was supplied for 12 hours followed by dark for 12 hours. These findings suggest that seeding rates of native perennial grasses should be high when seeding smooth brome invaded riparian zones. In addition, planting seeds from human disturbed ecosystems will likely yield high seedling establishment. Finally, when possible, managers should use drill- instead of broadcast-seeding because lower light availability in the first few growing days should produce high numbers of native perennial grasses.

Technical Abstract: The ecological integrity of riparian areas is reduced by biological plant invaders like smooth brome grass (Bromus inermis). Smooth brome actively invades recently disturbed riparian zones by its high seed production and fast seedling establishment. Restoring native perennial grasses to these regions is challenging because continual disturbances along riparian corridors open safe sites for further plant invasions. Identifying growth traits of common native perennial grasses, like western wheatgrass (Pascopyrum smithii), compared to smooth brome should provide managers necessary information on smooth brome invasion and restoration. In this study, we sought to identify how the germination timing and rates of smooth brome and western wheatgrass were affected by seed site location and light availability. Regardless of site or light dynamics, we found that smooth brome grass germinated two days earlier and at five-times higher rates than western wheatgrass. Sites that had high levels of anthropogenic disturbances also had high seedling germination rates for both smooth brome and western wheatgrass. In addition, when light was restricted for the first few growing days, seedling germination of both species were higher than in diurnal light environments. These findings suggest that seeding rates of native perennial grasses should be high when seeding smooth brome invaded riparian zones. In addition, planting seeds from anthropogenically disturbed ecosystems will likely yield high seedling establishment. Finally, when possible, managers should use drill- instead of broadcast-seeding because lower light availability in the first few growing days should produce high densities of native perennial grasses.