Role of propagule pressure and priority effects on seedlings during invasion and restoration of shrub-steppe

摘要: Plant invasion and restoration outcomes are largely driven by the timing magnitude of seed dispersal, performance dispersed species in an environment. Because dispersal controls recruitment newly arriving facilitates safe site occupation, assembly will differ depending on processes variable environmental conditions. The objective this study was to identify how annual perennial grasses assembled when times, propagule pressure, water availability were modified. To assess these effects, we conducted a field experiment grass invaded shrub-steppe ecosystem eastern Oregon. We tested effects seeding autumn or delaying until spring, adding water, varying rate 150, 1,500, 2,500, 3,500 seeds m−2 seedling emergence through time final density biomass. Providing priority effect spring initially facilitated establishment, but did not persist into second growing season. found that if pressure exceeded 150 m−2, limited. In addition, higher increased dependent upon pressure. These findings suggest dominated systems is more existing than grasses, availability.