In a restoration project, the State Coastal 

 Conservancy provided funds to replace about 

 10 acres of weedy vegetation with native 

 plants in the disturbed upland area that is now 

 the Visitor Center site. Burning was 

 attempted without success; disking was then 

 used to remove the weeds (mostly 

 Chrysanthemum spp.)- Native plant seeds 

 were sown, but the weedy species reinvaded 

 rapidly, and only a few native plants became 

 established. 



Plans to build a Visitor Center on the site 

 included regrading and landscaping with native 

 vegetation. This final effort was directed by 

 NERR Manager Paul Jorgensen and imple- 

 mented with irrigation, repeated transplanta- 

 tion efforts, dozens of volunteers, including 

 school children, donated plants, and continual 

 weeding. The effort has been substantial, but 

 it has produced a diverse native plant garden 

 over much of the site. It is clear that planting 

 is a small part of what is needed to reestablish 

 native vegetation. Drought and exotic species 

 pose major limits for success, and continual 

 attention is needed to maintain the desired 

 species and exclude the weeds. 



• Lower nitrogen fixation rates at the 

 marsh soil surface (which indicates low 

 organic matter/energy supplies for N- 

 fixers) and elevated nitrogen fixation rates in 

 the rhizosphere (which indicates low 

 concentrations of inorganic nitrogen in the 

 soil), as documented by Zalejko (1989). 



• Short cordgrass stature and unsuit- 

 ability for clapper rail nesting (Zedler, in 

 review). 



• Herbivore outbreaks and decimation of 

 transplanted cordgrass, presumably due to 

 the absence of the natural predators (PERL, 

 unpubl. data). 



• Low abundance of epibenthic in- 

 vertebrates, which indicates impaired food- 

 chain support functions (Rutherford 1989). 



• Invasion of newly constructed habitats 

 by exotic species, e.g., Japanese mussels 

 (potentially a dominant in the subtidal 

 benthos; Rutherford 1989), yellowfin goby 

 (a carnivore of unknown impact in wetland 

 channels; PERL, unpubl. data), and weedy 

 plant species (especially near freshwater 

 inflows; PERL, unpubl. data). 



6.5.2 Projects at San Diego Bay 



Two large mitigation projects are 

 underway at Sweetwater Marsh National 

 Wildlife Refuge along the eastern shore of San 

 Diego Bay. Both include the goal of creating 

 nesting habitat for the light-footed clapper 

 rail. One is a 12-acre site with 8 marsh 

 islands constructed in 1984 and planted with 

 cordgrass in 1985. The second is a 17-acre 

 site excavated from dredge spoils in 1990 and 

 planted with cordgrass in 1991. A research 

 program funded by the California Sea Grant 

 College and Caltrans has evaluated ecosystem 

 development and initiated experiments to 

 improve plant growth. The shortcomings of 

 the sites have been documented. They include: 



• Poor cordgrass growth due to 

 insufficient soil nitrogen and soil organic 

 matter (Langis et al. 1991, Cantilli 1989, 

 Langis and Zedler 1991). 



6.5.3 Why Habitat Restoration is Difficult 



There are many reasons why restoration 

 projects are hard to plan and why success is 

 difficult to achieve. Among them are the 

 following: 



• We are trying to construct in a short 

 time a system that developed in the absence of 

 man over about 5,000 years. 



• We don't know how the current wetlands 

 developed--there are no blueprints to 

 indicate how the topography developed, what 

 species arrived first, what processes 

 occurred to shape existing communities, what 

 rare and extreme events influenced the 

 occurrence and abundance of species. 



• We don't know the dependencies among 

 the components of the wetland-how species 

 tolerate or depend on specific environmental 



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