UBC Theses and Dissertations
Increased salinity decreases annual gross primary productivity of a Northern California brackish wetland Russell, Sarah
Brackish wetland plant and microbial communities are a diverse mix of freshwater- and saltwater-adapted species in competition with each other. This has led researchers to predict that carbon cycling in brackish wetlands may be more resilient to changes in salinity than in fresh- or saltwater systems. Rush Ranch, a brackish tidal wetland near Suisun Bay, California, experienced drought-induced salinization in the 2015 and 2016 growing seasons followed by a freshwater flushing event in 2017. During the drought, salinity rose from the baseline of 4.5 ppt to an average of 10.3 ppt, peaking at 12.5 ppt. During these summers, gross primary productivity (GPP) decreased by 30%. Stepwise linear regression revealed that salinity was a major driver of GPP at this brackish wetland. We trained a random forest model to predict GPP based on environmental data from low salinity years. Naive to the salinization event, the model over-predicted GPP during high salinity years. These results provide ecosystem-scale evidence that increased salinity can decrease GPP at brackish tidal wetlands. This relationship is a starting point for incorporating the effect of changes in salinity on GPP in wetland carbon models, which could improve wetland carbon forecasting and management for climate resilience.
Item Citations and Data
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