Effect of habitat and plant position relative to the soil surface on survival of Basin Wildrye Seedlings (Leymus cinereus)

The initial survival of basin wildrye (Leymus cinereus (Scribn. & Merr.) A. Löve [Poaceae]) plugs used in restoration of riparian habitats in the Crooked River National Grassland in northeastern Oregon was strongly associated with habitat type and planting depth. Five plots in each of 4 study areas were assessed. Survival was strongly dependent on habitat, ranging from 18.8% at the lowest elevation to 70.5% at the highest elevation. Northern pocket gophers (Thomomys talpoides (Richardson) [Geomyidae]) were considered a major cause of mortality, while mortality by cattle (Bos taurus Bojanus [Bovidae]) grazing was significant at only one habitat. The lowest elevation habitat had a sandy loam soil with few rocks and strong evidence of gopher activity, whereas the highest elevation habitat had a rocky sandy loam soil with weak evidence of gophers. The highest elevation habitat had burned, which likely reduced competition. Survival of plants that were buried (69%) or with the top of the plug surface flush with the soil surface (53%) was significantly greater than for plants with some of the plug root mass above the soil surface (about 14%). Improved survival of L. cinereus plugs will likely be realized with control of gophers and cattle; additionally survival can be improved by ensuring plug surfaces are flush with the soil surface or buried by a few centimeters of soil.