Assistant Professor Rider University Lawrenceville, New Jersey
Body of Abstract: Coastal salt marsh communities provide valuable ecosystem services such as erosion prevention and essential habitat for coastal wildlife, but are particularly vulnerable to the threats of climate change. This work investigates the combined effects of two climate stressors, elevated CO2 (eCO2) and temperature, on leaf physiological traits of dominant salt marsh plant species. The research took place in the Kirkpatrick Marsh at the Smithsonian Environmental Research Center, which includes two plant communities: a C3 sedge community and a C4 grass community. This experiment consists of 24 plots arranged across a heating gradient consisting of unheated ambient plots and plots that are heated to 1.7, 3.4, and 5.1 °C above ambient. In the C3 community, there are six additional plots with eCO2 chambers, half at ambient temperatures and half heated to +5.1 °C above ambient. Here we present data collected over four years on rates of stomatal conductance (gs), from which we can make indirect assumptions about plant productivity and water use efficiency. We found a significant negative effect of warming on gs of both C3 and C4 plants, and eCO2 treatments also led to lower gs in C3 plants. However, the negative effect of warming on gs of C3 plants lessened over the four years of measurements, indicating that the sedges may be acclimating to the warming treatment. On the other hand, the site has also received higher than average rainfall over the course of the experiment, so it is also possible that changes in salinity exposure may be driving this response. These results suggest future declines in plant photosynthetic productivity of C4 communities, with lesser declines in C3 sedges. Based on these results, land managers may want to focus on establishing C4 communities in restored marshlands that are projected to experience warm, wet summers under future climate scenarios.