Influence of elevation and inundation on tidal wetland vegetation distributions in the northern San Francisco Bay Estuary

Friday, August 10, 2007 - 9:20 AM

COS 148-5: Influence of elevation and inundation on tidal wetland vegetation distributions in the northern San Francisco Bay Estuary

Lisa M. Schile¹, Tim Carson², John C. Callaway³, Philip Bachand², V. Thomas Parker¹, Jeremy P. Lowe⁴, Michael Vasey¹, and Stuart Siegel². (1) San Francisco State University, (2) Wetlands and Water Resources, (3) University of San Francisco, (4) Philip Williams and Associates

Tidal wetland restoration efforts have focused on establishing appropriate elevations for plant colonization, with the assumption that elevation determines inundation rates and other critical factors for plant establishment and growth. While elevation is the key factor driving inundation rates, within-site variation due to impoundments, pannes and other features also affect local flooding and draining. Substantial research has evaluated elevational distributions of tidal wetland plants in San Francisco Bay wetlands; however, little work has directly linked elevation to patterns of inundation across a tidal wetland. We evaluated plant distributions across five tidal wetlands in the northern San Francisco Bay Estuary. Plant and elevation surveys were conducted at 200-500 points around three to four water level stations per site. Inundation data were collected for approximately one year. Data were combined in 5-cm intervals according to tidal elevations, and mean and maximum depth and duration of inundation were calculated for each interval. Patterns of vegetation zonation were apparent from our data, with species showing peaks in distributions across the tidal wetlands. For example, Sarcocornia pacifica had the most widespread elevational distribution, with a number of species occurring at slightly lower elevations, including Spartina foliosa, Typha angustifolia, Bolboschoenus maritimus, and Schoenoplectus acutus. There was substantial overlap and spatial variability in distributions relative to both elevation and inundation patterns for some dominant species. We found little evidence for critical thresholds for plant distributions across all wetlands, although, there is evidence that plants respond to minor changes in elevation and inundation.

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