9619875 Zedler Conservation biologists focus on protecting biodiversity and ecosystem management, yet there is little understanding of the linkage between the numbers of species present and how an ecosystem functions. Recent experiments demonstrate that where more species are present, biomass is higher, more nutrients are retained, and drought resistance is greater. Unanswered are questions regarding the type of species, the impacts on the most critical functions, and how knowledge of diversity-function relationships might be used to improve habitat restoration efforts. An unusual opportunity exists to facilitate field experimentation with salt marsh vegetation in the Tijuana Estuary in southern California and to make the results of these experiments relevant to restoration ecology. A new restoration site, a salt marsh plain, will be excavated in 1996 at the Tijuana River National Estuarine Research Reserve. Experiments designed to investigate the effects of species richness and composition on ecosystem function will be conducted at this site. Results from these experiments will then be directly applied to the restoration project. The test of how species richness affects ecosystem functioning relates directly to the basic conservation tenet that diversity matters. Beyond this, the work will have an impact on restoration ecology. Determining whether monospecific types or specific combinations of species provide desired ecosystem functions will suggest tools for accelerating nitrogen accumulation. The importance of restoration for purposes of sustaining southern California's biodiversity is indicated by the magnitude of mitigation funds being required to restore coastal wetlands. Furthermore, locating the field experiments in the Research Reserve will facilitate follow-up studies of long-term community dynamics, including colonization by other plant and animal species.
