Gross XXXX production drives net @entity3810 fluxes across a salt marsh landscape.

@entity1568 @entity3727 @entity26 @entity1507 @entity3810 @entity68
UNASSIGNED: Sea level rise will change inundation regimes in salt marshes, altering redox dynamics that control nitrification-a potential source of the potent greenhouse gas, @entity3810 ( @entity3727 )-and denitrification, a major @entity1568 (N) loss pathway in coastal ecosystems and both a source and sink of @entity3727 . Measurements of net @entity3727 fluxes alone yield little insight into the different effects of redox conditions on @entity3727 production and consumption. We used in situ measurements of gross @entity3727 fluxes across a salt marsh elevation gradient to determine how soil @entity3727 emissions in coastal ecosystems may respond to future sea level rise. Soil redox declined as marsh elevation decreased, with lower soil @entity1507 and higher ferrous @entity68 in the low marsh compared to the mid and high marshes (p < 0.001 for both). In addition, soil @entity26 concentrations were lower in the low and mid marshes relative to the high marsh (p < 0.001). Net @entity3727 fluxes differed significantly among marsh zones (p = 0.009), averaging 9.8    5.4  g N m(-2) h(-1) , -2.2    0.9  g N m(-2) h(-1) , and 0.67    0.57  g N m(-2) h(-1) in the low, mid, and high marshes, respectively. Both net @entity3727 release and uptake were observed in the low and high marshes, but the mid marsh was consistently a net @entity3727 sink. Gross @entity3727 production was highest in the low marsh and lowest in the mid marsh (p = 0.02), whereas gross @entity3727 consumption did not differ among marsh zones. Thus, variability in gross @entity3727 production rates drove the differences in net @entity3727 flux among marsh zones. Our results suggest that future studies should focus on elucidating controls on the processes producing, rather than consuming, @entity3727 in salt marshes to improve our predictions of changes in net @entity3727 fluxes caused by future sea level rise. This article is protected by copyright. All rights reserved.
