Short-hydroperiod freshwater marsh ecosystems in Everglades are characterized by a ~half-year long inundation period while water level stays below soil surface in the remaining period of a year. The ecosystem has been demonstrated to be a CO2 sink in previous studies. The seasonal patterns of net ecosystem CO2 exchange (NEE) are mainly controlled by hydrologic features, such as water depths. In 2016, as a result of a combination of high precipitation and activities of water management, large areas of the short-hydroperiod freshwater marsh in Everglades experienced an extended inundation period that lasted for > 12 months. Due to a lack of knowledge on how inundation duration influences the ecosystem carbon processes, the impact of this extreme inundation event remained unknown. In this study, we aimed to answer 1) what are the effects of water depth and inundation duration on the component of NEE, i.e. gross ecosystem CO2 exchange (GEE) and ecosystem respiration (ER)? And 2) how does the extended hydroperiod in 2016 (> 12 months) affected the ecosystem CO2 balance? The 10-year eddy covariance data (2008-2016) were used from a short-hydroperiod freshwater marsh ecosystem at Taylor Slough in Everglades.
Results/Conclusions
The preliminary results show that an increase in water level inhibited GEE and ER simultaneously and, overall, had limited effects on NEE. A prolonged inundation period substantially decreased GEE; however, the ER was irresponsive to the extension of inundation period. Consequently, the extended inundation (>12 months) in 2016 turned the ecosystem from a CO2 sink (as observed in other years) to a source. The Comprehensive Everglades Restoration Plan aims to increase freshwater flow to Taylor Slough to restore the landscape and reduce saltwater intrusion from Florida Bay. This water management activity is expected to increase water levels and inundation periods in the short-hydroperiod freshwater marshes in Everglades. This research provides evidence showing that extending inundation period would weaken the ecosystem CO2 uptake and release more greenhouse gas into the atmosphere.