Grassland species vary in tolerance to stressors associated with climate change
Climate change effects shift distributions of grass species that stabilize coastal sediments and offer protection to inland communities. Coastal species are sensitive to climate change as they are influenced by both atmospheric and oceanic drivers (i.e. changes in temperature, precipitation, and sea level rise). To understand the tolerance of coastal grasses to climate change stressors, our objective was to quantify responses of two dominant grassland species (Spartina patens and Fimbristylis spadicea) to saline flooding and drought stress. Field collected plants (n = 6) were subjected to varying levels of saline flooding (2, 5, 10, 15, and 20 g L-1) and drought (well watered vs water withheld). Weekly measurements were taken for functional traits and physiological responses, which included stomatal conductance (gs), electron transport rate (ETR), water potential (ψ), tissue chlorides, and specific leaf area (SLA).
Both species exhibited physiological responses to increased salinity. Stomatal conductance (gs) reduced significantly following initial treatment exposure and recovered briefly. Spartina patens recovered at levels of 5 g L-1 and F. spadicea recovered at levels of 10 g L-1. SLA declined in both S. patens and F. spadicea, but was more reduced in F. spadicea. ETR significantly decreased for both S. patens and F. spadicea. Tissue chlorides were highest in saline flooded F. spadicea plants compared to S. patens. Drought treated plants had significant declines in gs, ETR, and ψ. Overall, Spartina patens was more tolerant to saline flooding and drought treatments than F. spadicea. This outcome reflects the varied distribution of S. patens from drought induced dune environments to saline flooded marshes. Spartina patens is highly responsive to effects associated with atmospheric and oceanic drivers of climate change and is an important species in shaping coastal communities.