Component-specific dynamics of riverine mangrove CO2 efflux in the Florida coastal Everglades

•Black mangrove pneumatophores contributed the largest average CO2 flux.•Tidal inundation reduced soil CO2 flux.•Flooding increased the partial pressure of CO2 observed in the overlying surface water.•Below-canopy components contributed between 45% and 65% of total ecosystem respiration.•Scaling cha...

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Published in:Agricultural and forest meteorology 2015-11, Vol.213, p.273-282
Main Authors: Troxler, Tiffany G., Barr, Jordan G., Fuentes, Jose D., Engel, Victor, Anderson, Gordon, Sanchez, Christopher, Lagomasino, David, Price, René, Davis, Stephen E.
Format: Article
Language:English
Subjects:
Avicennia germinans
Budget
Carbon
Carbon dioxide
Course woody debris
Cycles
Flux
Forests
pCO2
Peat
Pneumatophore
Respiration
Salinity
Soil (material)
Surface water
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Summary:•Black mangrove pneumatophores contributed the largest average CO2 flux.•Tidal inundation reduced soil CO2 flux.•Flooding increased the partial pressure of CO2 observed in the overlying surface water.•Below-canopy components contributed between 45% and 65% of total ecosystem respiration.•Scaling chamber-based flux was useful to constrain mangrove ecosystem respiration. Carbon cycling in mangrove forests represents a significant portion of the coastal wetland carbon (C) budget across the latitudes of the tropics and subtropics. Previous research suggests fluctuations in tidal inundation, temperature and salinity can influence forest metabolism and C cycling. Carbon dioxide (CO2) from respiration that occurs from below the canopy is contributed from different components. In this study, we investigated variation in CO2 flux among different below-canopy components (soil, leaf litter, course woody debris, soil including pneumatophores, prop roots, and surface water) in a riverine mangrove forest of Shark River Slough estuary, Everglades National Park (Florida, USA). The range in CO2 flux from different components exceeded that measured among sites along the oligohaline-saline gradient. Black mangrove (Avicennia germinans) pneumatophores contributed the largest average CO2 flux. Over a narrow range of estuarine salinity (25–35 practical salinity units (PSU)), increased salinity resulted in lower CO2 flux to the atmosphere. Tidal inundation reduced soil CO2 flux overall but increased the partial pressure of CO2 (pCO2) observed in the overlying surface water upon flooding. Higher pCO2 in surface water is then subject to tidally driven export, largely as HCO3. Integration and scaling of CO2 flux rates to forest scale allowed for improved understanding of the relative contribution of different below-canopy components to mangrove forest ecosystem respiration (ER). Summing component CO2 fluxes suggests a more significant contribution of below-canopy respiration to ER than previously considered. An understanding of below-canopy CO2 component fluxes and their contributions to ER can help to elucidate how C cycling will change with discrete disturbance events (e.g., hurricanes) and long-term change, including sea-level rise, and potential impact mangrove forests. As such, key controls on below-canopy ER must be taken into consideration when developing and modeling mangrove forest C budgets.
ISSN:0168-1923
1873-2240
DOI:10.1016/j.agrformet.2014.12.012