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Open Access Publications from the University of California

Facilitation Between Non-indigenous Species: Smooth Cordgrass and Invertebrates


Non-indigenous species threaten California’s coastal quality through impacts on habitat structure, migratory species, and commercial fisheries. Atlantic smooth cordgrass (Spartina alterniflora) has invaded San Francisco Bay, and is poised to invade other central coast marshes. It fills in mudflats used by migratory shorebirds and may change the invertebrate prey available to them as well. Some evidence suggests that non-indigenous species, such as smooth cordgrass, may change their surrounding habitat by changing physical structure or soil chemistry in a way that helps other non-indigenous organisms survive at the expense of native species, a process termed facilitation. However, there has been little quantitative work on facilitation. This study examines the effects of smooth cordgrass on invertebrates in San Francisco Bay, and may help predict its future impact in other marshes. My project uses both observational and manipulative methods, including measures of vegetation characteristics, invertebrate abundance and species diversity, colonization, and spread of smooth cordgrass patches. Understanding facilitation between non-indigenous species can allow coastal managers to focus control efforts on those species which have the most impact. This information will also be useful in wetland restoration projects which must content with invasion by smooth cordgrass. This project will bridge science and policy by providing basic ecological data on the occurrence of facilitation among non-indigenous species in salt marshes as well as data that managers can apply to prioritizing control efforts.

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