摘要:Salt marshes are among the most productive ecosystems on Earth, and
play an important role in the global carbon cycle. Net carbon dioxide
(CO2) ecosystem exchanges in coastal salt marshes remain poorly investigated. In Spartina
alterniflora dominated North American Atlantic coast marshes, the lack of a clear
understanding of how Spartina alterniflora responds to flooding limits our current
ability to understand and predict salt marsh response to sea-level rise. Here we
investigate the processes influencing ecosystem-level carbon exchanges between a
S. alterniflora dominated salt marsh on the eastern shore of Virginia and the atmosphere.
We examined the impacts of tidal inundation on the marsh–atmosphere carbon
exchanges through a combination of eddy covariance measurements and in situ
photosynthetic measurements. Maximum daytime carbon fluxes were observed
during the middle of the growing season (July and August) and amounted to
−10 μmol CO2 m−2 s−1, and the marsh
assimilated 130 gC m−2 during the 2007 growing season. Our study is the first to quantify the effects
of tidal inundation on marsh plants, which caused anywhere from 3% to
91% reductions in atmospheric carbon fluxes, with a mean reduction of
46 ± 26%, when compared to non-flooded conditions.