Response and Recovery of Low-Salinity Marsh Plant Communities to Presses and Pulses of Elevated Salinity
In estuaries, future variation in sea level and river discharge will lead to saline intrusion into low-salinity tidal marshes. To investigate the processes that control the differential response and recovery of tidal freshwater marsh plant communities to saline pulses, a 3 × 5 factorial greenhouse experiment was conducted to examine the effects of a range of salinity levels (3, 5, and 10 practical salinity units (PSU)) and pulse durations (5, 10, 15, 20, and 30 days per month) on community composition of tidal freshwater marsh vegetation. Recovery of perturbed communities was also examined after 10 months. The results showed that community composition was increasingly affected by the more-saline and longer-duration treatments. The increasing suppression of salt-sensitive species resulted in species reordering, decreased species richness, and decreased aboveground biomass. Most of the plant species were able to recover from low-salinity, short-duration saline pulses in less than 1 year. However, because not all species recovered in the heavily salinized treatments, species richness at the end of the recovery period remained low for treatments that were heavily salinized during the treatment period. In contrast, plant aboveground biomass fully recovered in the heavily salinized treatments. Although the magnitude and duration of pulsed environmental changes had strong effects on community composition, shifts in community composition prevented long-term reductions in productivity. Thus, in this study system, environmental change affected species composition more strongly than it did ecosystem processes.
KeywordsDisturbance Salinization Freshwater marsh Composition Productivity
This material is based upon work supported by the National Science Foundation through the Georgia Coastal Ecosystems Long-Term Ecological Research program under Grant No. OCE-1237140 and a Sigma Xi Grant-in-Aid-of-Research. We thank Wei-Ting Lin, Shanze Li, Jacob Shalack, Caroline Reddy, Dontrece Smith, Timothy Montgomery, Sasha Greenspan, Eric Weingarten, Narissa Turner, Jonathan Adams, and GCE-LTER Schoolyard participants for help with this project. This is contribution number 1074 from the University of Georgia Marine Institute.
FL and SCP conceived and designed the experiments. FL performed the experiments and analyzed the data. FL and SCP wrote the manuscript.
- Ciais, P., M. Reichstein, N. Viovy, A. Granier, J. Ogee, V. Allard, M. Aubinet, N. Buchmann, C. Bernhofer, A. Carrara, F. Chevallier, N. De Noblet, A.D. Friend, P. Friedlingstein, T. Grunwald, B. Heinesch, P. Keronen, A. Knohl, G. Krinner, D. Loustau, G. Manca, G. Matteucci, F. Miglietta, J.M. Ourcival, D. Papale, K. Pilegaard, S. Rambal, G. Seufert, J.F. Soussana, M.J. Sanz, E.D. Schulze, T. Vesala, and R. Valentini. 2005. Europe-wide reduction in primary productivity caused by the heat and drought in 2003. Nature 437 (7058): 529–533.CrossRefGoogle Scholar
- Cloern, J.E., and A.D. Jassby. 2012. Drivers of change in estuarine-coastal ecosystems: discoveries from four decades of study in San Francisco Bay. Reviews of Geophysics 50, 4.Google Scholar
- Crain, C. M., B. R. Silliman, S. L. Bertness, and M. D. Bertness. 2004. Physical and biotic drivers of plant distribution across estuarine salinity gradients. Ecology 85:2539-2549.Google Scholar
- Herbert, E. R., J. Schubauer-Berigan., and C. B. Craft. 2018. Differential effects of chronic and acute simulated seawater intrusion on tidal freshwater marsh carbon cycling. Biogeochemistry, 1–18.Google Scholar
- Li, F. 2017. Mesocosm experiment on fresh marsh plant community responses to salinity pulses in 2014 and 2015. Georgia Coastal Ecosystems LTER Project; University of Georgia; Long Term Ecological Research Network. doi: https://doi.org/10.6073/pasta/c48f9dffc45b8595378eb45382dbc2e3.
- Li, F., and S. Pennings. 2018. Responses of tidal freshwater and brackish marsh macrophytes to pulses of saline water simulating sea level rise and reduced discharge. Wetlands: 1–7.Google Scholar
- Spaak, J.W., J.M. Baert, D.J. Baird, N. Eisenhauer, L. Maltby, F. Pomati, V. Radchuk, J.R. Rohr, P.J. Van den Brink, and F. De Laender. 2017. Shifts of community composition and population density substantially affect ecosystem function despite invariant richness. Ecology Letters 20 (10): 1315–1324.CrossRefGoogle Scholar