Interactive effects of hydrology and salinity on oligohaline plant species productivity: Implications of relative sea-level rise |
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| Authors: | E A Spalding M W Hester |
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| Institution: | (1) National Marine Fisheries Service, NOAA, 646 Cajundome Blvd, Lafayette, LA 70506, USA;(2) Biology Department, University of Louisiana at Lafayette, Lafayette, LA, USA;(3) School of Renewable Resources, Louisiana State University, Baton Rouge, LA, USA |
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| Abstract: | Sea-level rise is anticipated to alter hydrologic and salinity regimes of coastal wetlands. We conducted a mesocosm experiment
to determine species-level responses to 12 sea-level rise scenarios. Both hydrologic regime (−10, +5, and +20 cm flooding
depth) and salinity level (fresh, 2‰, 4‰ and 6‰) were interactively manipulated. Within these various sea-level rise scenarios,
we sought to determine the effects of hydrologic regime, salinity level, and the interaction of these two stresses on the
productivity ofPanicum hemitomon, Sagittaria lancifolia, andSpartina patens, which are dominant macrophytes of fresh, intermediate, and brackish marsh types, respectively, in coastal Louisiana and
the southeastern coastal plain. We found that altered hydrologic regimes and increased salinity levels differentially affected
edaphic conditions and species-level productivity. Increases in flooding depth were most detrimental toS. patens. Salinity levels greater than 4‰ resulted in mortality ofP. hemitomon, and salinity levels of 6‰ resulted in reduced growth and eventual death, ofS. lancifolia. The effects of elevated salinity levels onP. hemitomon andS. lancifolia were exacerbated when coupled with increased flooding levels. Although soil organic matter was shown to increase in all vegetative
conditions, increases were dependent upon the productivity of the species under the different hydrologic regimes and salinity
levels withP. hemitomon displaying tremendous potential to increase soil organic matter under fresh conditions, especially when coupled with moderate
flooding. The results of this study indicate that as plant communities are subjected to long-term changes in hydrology and
salinity levels, community productivity and sustainability ulimately will be determined by species-level tolerances in conjunction
with species interactions. |
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