Disturbance for endangered parasitic plant restoration is offset by salt marsh invasion

I present results of an experimental reintroduction of an endangered parasitic plant to a restoration site in the San Francisco Estuary. In four years of field experiments, I tested disturbance management methods for enhancement of rare plant establishment and fitness. I identified critical life stages and used life table survival analysis and accelerated failure time models to assess population establishment and restoration management actions. Vegetation gap creation is a successful restoration technique that will enhance rare plant establishment and fitness, but the benefits can be offset by exotic plant invasions. Results demonstrate that successful restoration requires a unique host community to support the introduced parasite load. High seedling mortality was strongly correlated with the presence of exotic winter annual grasses that are unsuitable hosts for endangered root hemiparasites. Seedling survival and adult fecundity were further reduced under muted tidal regimes. Seven years following reintroduction both restored and reference populations are impacted by multiple invasive weed species. These results indicate a critical need for regional invasive plant control and restoration of historic tidal regimes for endangered plant recovery and salt marsh restoration.