Conclusion
Here, we implemented vegetation response functions to salinity and
inundation to improve representation of coastal marsh ecosystems in a
land surface model. In general, representing the responses of salt marsh
photosynthesis to salinity and flooding via resistance to root water
uptake worked well and is consistent with known plant physiological
responses. Incorporating vegetation responses to salinity and inundation
improved the accuracy of simulated GPP, but the updated model still
overestimates productivity of freshwater wetlands. Vegetation responds
to salinity and water level via several mechanisms beyond root water
uptake, so our model improvements do not capture the complete vegetation
response, but they provide a foundation to which additional mechanisms
can be added. The stimulation of salt marsh productivity under moderate
increases in inundation still needs to be addressed, as does the
overestimation of productivity in freshwater marshes. Nevertheless, this
work opens the door for modeling wetland C uptake along estuarine
transects that include saline, brackish, and fresh marshes, or at
different latitudes and tidal regimes. Additionally, salinity and
flooding parameters could be applied to upland vegetation occurring at
marsh edges that are much more sensitive to salinity and flooding to
simulate carbon dynamics with saltwater intrusion or increasing
hydroperiods.
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