Transplantations and relocation of species at risk: learning from the past to plan for the future
Grewell, Brenda , Espeland, Erin .
Plant reintroduction in changing environments: the case of endangered Chloropyron molle subsp. molle (Orobanchaecae) in weed-invaded estuarine wetlands.
Periodic habitat disturbance is critical to the persistence of many rare annual plant species. Chloropyron molle subsp. molle (Soft bird’s-beak; Orobanchaceae ) is an endangered, annual root hemiparasite narrowly restricted to drained high marsh plains and ecotones within relict tidal wetlands of the San Francisco Estuary, California. This hemiparasite reduces the dominance of its host plants and thus facilitates plant species diversity within salt marshes. We conducted an experimental population reintroduction of soft bird’s-beak to develop a model for estuary-wide recovery efforts and tidal wetland restoration. We studied extant populations and characteristics of occupied habitat to screen reintroduction site suitability. In four years of field experiments, disturbance management methods were tested to enhance establishment success and overall fitness of soft bird’s-beak. Sowing seeds into created vegetation gaps enhances plant establishment, but successful restoration requires a unique host community that does not include exotic plants. Demographic monitoring and survival analysis models revealed that the seedling stage is the most critical for population persistence. High seedling mortality was strongly correlated with anthropogenically-muted tidal regimes and the presence of exotic winter annual grasses that are parasitized, but unsuitable hosts. Twelve years following the reintroduction, aggressive invasion of Lepidium latifolium (perennial pepperweed) is also impacting both reintroduced and historic soft bird’s-beak populations. These results indicate a critical need for active stewardship, regional invasive plant control, and restoration of variable tidal regimes for salt marsh plant recovery. Future sea level rise suggests we must adopt a dynamic view of how habitat supports at risk species. For annual plants that show large fluctuations in census sizes, projections of the seed bank size needed to maintain reintroduced populations through changing conditions are needed and may be quite large. Soft bird’s-beak reintroduction provides an important case study because periodic disturbance is critical to the species, multiple drivers of environmental change are affecting occupied habitat, and planning for inevitable habitat change is also important for every plant species considered for transplantation.
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1 - USDA-ARS Exotic & Invasive Weeds Research Unit, University of California Davis, Dept of Plant Sciences MS-4, 1 Shields Ave. , Davis, CA, 95616, USA
2 - USDA-ARS NPARL Pest Management Research Unit, 1500 N. Central Ave., Sidney, MT, 59270, USA
Presentation Type: Symposium or Colloquium Presentation
Location: Delaware A/Hyatt
Date: Wednesday, July 11th, 2012
Time: 10:15 AM