Interaction between salinity and inundation on Sarcocornia pacifica productivity: Implications for climate change

We investigated factors controlling primary production of pickleweed, Sarcocornia pacifica (formerly Salicornia virginiana), a dominant high marsh plant species in the saline reaches of the San Francisco Bay Estuary.  Three sites were chosen along a salinity gradient in the Bay. In February 2005, we established 20-1.5 m x 1.5 m plots at each site in monospecific S. pacifica stands of uniform height and subdivided each plot into 9-0.25 m2 subplots.  Half of the plots werre near channels and half were located in poorly drained sites away from channels.  We collected S. pacifica aboveground biomass and soil salinity (5, 10, and 20 cm depth) four times throughout the growing season.  ANPP was calculated by subtracting the pre-growing season biomass from the peak biomass.  We examined the effects of site, channel proximity and pore water salinity on ANPP.  There was no significant effect of site on ANPP, however, plots located close to channels had significantly greater biomass than those away from channels.  Salinity had no measurable effect on plants near channels, but had a strong negative impact on ANPP in plots located away from channels.  These results suggest that hydrological dynamics may have more influence over ANPP of S. pacifica than landscape position in the SF Bay Estuary salinity gradient.  Given model predictions of increased salinity and inundation for the SF Bay-Delta Estuary, climate change will likely have a considerable negative impact on wetland productivity, more than expected.