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Fading to Blue : Effects of Inundation and Salinity on Tidal Marsh Vegetation

Fading to Blue : Effects of Inundation and Salinity on Tidal Marsh Vegetation. V.T. Parker, L.M. Schile, J.C. Callaway & M.C. Vasey San Francisco State University and University of San Francisco. San Francisco Bay Tidal Marshes. Brackish Marshes. Freshwater Marshes in the Delta.

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Fading to Blue : Effects of Inundation and Salinity on Tidal Marsh Vegetation

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  1. Fading to Blue: Effects of Inundation and Salinity on Tidal Marsh Vegetation V.T. Parker, L.M. Schile, J.C. Callaway & M.C. Vasey San Francisco State University and University of San Francisco

  2. San Francisco Bay Tidal Marshes Brackish Marshes Freshwater Marshes in the Delta Salt Marshes Summer Water Salinity (ppt) Figure adapted from Noah Knowles 0 5 10 15 20 25 30 35

  3. Historic marshes along gradient Browns Island China Camp Coon Island

  4. Restored marshes along the gradient Carls Bull Island Pond 3 Pond 2A

  5. San Francisco Bay Tidal Marshes Species Diversity Brackish Marshes Freshwater Marshes in the Delta Salt Marshes Species Diversity Species Diversity Species Diversity 2-22 species 27-37 species 117+ species Summer Water Salinity (ppt) Figure adapted from Noah Knowles 0 5 10 15 20 25 30 35

  6. San Francisco Bay Tidal Marshes Annual Primary Production Brackish Marshes Freshwater Marshes in the Delta Salt Marshes ANPP ANPP ANPP 700-1300 g m-2 yr-1 200-800 g m-2 yr-1 1300-2500 g m-2 yr-1 Summer Water Salinity (ppt) Figure adapted from Noah Knowles 0 5 10 15 20 25 30 35

  7. SF Bay-Delta:Freshwater> Salt Marshes • Freshwater tidal marshes have 5-50 times more species than salt marshes • Freshwater tidal marshes have 3-12 times more primary production • Historic marshes have more species than restored marshes

  8. What happens to these systems under projected climate change?

  9. Processes predicted to change…

  10. Temperature regime increases 6 global climate models for each of 4 different historic and future scenarios. Northern California will increase in temperature. The models are ambivalent about precipitation, but greater unpredictability Dettinger 2005

  11. Temperature effects on wetlands • Direct • Indirect

  12. Direct effects-temperature • Influence on photosynthesis/respiration balance of dominant plants respiration photosynthesis rate temperature

  13. Direct effects-temperature • Influence on photosynthesis/respiration balance of dominant plants Increase in ANPP rate Mortality Decrease in ANPP temperature

  14. Salinity (ppt) 35 10 15 20 25 30 5 0 Indirect Effects-temperature • Sierran snow pack melts earlier • Rivers flow earlier • Salinity increases upstream

  15. Salinity (ppt) 0 5 10 15 20 25 30 35 Projected Salinity Changes Critical Current Summer Salinities Projected Summer Salinities in 2060 Figure from Noah Knowles

  16. Salinity Effects • Shifts composition • Reduces diversity • Reduces productivity • Inhibits organic peat production • Changes soil structure • Critical thresholds at low salinity levels

  17. Indirect effects, cont. • Increase in the rate of sea level rise (from IPCC)

  18. Inundation and floodingcurrent conditions

  19. Marsh Surface Elevations: Percent Time Wet Restored Sites Reference Sites Browns Island Bull Island Coon Island Pond 2a Number of Observations Carl’s Marsh Restored sites are inundated more often than natural sites

  20. Marsh Surface Elevations: Plant Diversity Restored Sites Reference Sites Bull Island Browns Island MHW MHHW Pond 2a Coon Island Number of Species Carl’s Marsh Diversity peaks at MHHW at reference sites Mean high water - MHW Mean higher high water - MHHW

  21. Coon Island Within a site, elevation predicts distribution of species c c c c b b b b b b a a MTL MHW MHHW

  22. Schoenoplectus acutustule Larry Allian c b a a a a Formerly known as Scirpus acutus

  23. Bolboschoenus maritimusAlkali bulrush a b c d a b c c Formerly known as Scirpus maritimus

  24. Schoenoplectus americanusCommon three-square a a c b b a Formerly known as Scirpus americanus

  25. Sarcocornia pacificaPickleweed a c b a c a b c Formerly known as Salicornia virginica

  26. Site-level Elevation and Inundation Patterns • Restored sites differ in length of inundation, and elevation at which species diversity peaks • Elevation important in determining plant distributions within sites • Among sites, inundation patterns for any species are relatively similar, but elevations may differ • Salinity another influence needing consideration

  27. Given environmental change • If temperature increases… • If salinity increases… • If marsh substrate accretion fails to keep up with sea level rise and inundation increases… • What might be a predictable scenario for SF Bay-Delta?

  28. Sarcocornia pacifica: • Sarcocornia occurs in a diversity of salinity and inundation conditions formerly Salicorniavirginica

  29. Sarcocornia pacifica: • Used spatially variability as a natural experiment to ask the question: What happens to Sarcocornia productivity under higher salinities and more inundation? Multiple harvests to assess annual production under a variety of salinity and inundation conditions

  30. While annual productivity increases with height… The pattern with salinity seems scattered and complex…

  31. Until well-drained locations are separated from poorly-drained sites... Well-drained plots Poorly-drained plots

  32. Results: Natural Experiment • Increases in salinity and inundation (predicted environmental changes)… Result in significant reductions in wetland productivity in the species most likely to expand low productivity?

  33. Conclusions • Reducing the rate of change in wetlands: depends onmaintaining or enhancing freshwater flows into the Delta in the summer/fall periods (levee protection, less diversion) • Restoring new marshes sooner might increase their likelihood of long-term success and persistence

  34. To keep you getting stuck in the details…

  35. Global Warming Impact on SF Bay-Delta Increasing Temperatures Smaller Snowpack Ppt Shifts from Snow to rain Lower Summer flows Earlier melt Spring floods Increased inundation Reduced Peat formation Increased Estuarine salinity Sea level Rise

  36. these environmental changes impact wetland vegetation: …and potentially lead to:

  37. Acknowledgements: …CA Parks, CA Fish & Game, EB Regional Park District, a large and excellent field crew, and colleagues in the IRWM project meaning marshes may fade to blue Loss of species, reduction in annual productivity, with cascading effects on linked terrestrial and pelagic systems…

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