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Seasonal differences in the CO₂ exchange of a short-hydroperiod Florida Everglades marsh

Schedlbauer, Jessica L., Oberbauer, Steven F., Starr, Gregory, Jimenez, Kristine L.
Agricultural and forest meteorology 2010 v.150 no.7-8 pp. 994-1006
wetlands, carbon dioxide, gas exchange, ecosystems, dry matter accumulation, seasonal variation, dry season, wet season, salt marshes, macrophytes, flooded conditions, primary productivity, solar radiation, air temperature, carbon sequestration, cell respiration, water management, net ecosystem exchange, Florida
Although wetlands are among the world's most productive ecosystems, little is known of long-term CO₂ exchange in tropical and subtropical wetlands. The Everglades is a highly managed wetlands complex occupying >6000km² in south Florida. This ecosystem is oligotrophic, but extremely high rates of productivity have been previously reported. To evaluate CO₂ exchange and its response to seasonality (dry vs. wet season) in the Everglades, an eddy covariance tower was established in a short-hydroperiod marl marsh. Rates of net ecosystem exchange and ecosystem respiration were small year-round and declined in the wet season relative to the dry season. Inundation reduced macrophyte CO₂ uptake, substantially limiting gross ecosystem production. While light and air temperature exerted the primary controls on net ecosystem exchange and ecosystem respiration in the dry season, inundation weakened these relationships. The ecosystem shifted from a CO₂ sink in the dry season to a CO₂ source in the wet season; however, the marsh was a small carbon sink on an annual basis. Net ecosystem production, ecosystem respiration, and gross ecosystem production were −49.9, 446.1 and 496.0gCm⁻² year⁻¹, respectively. Unexpectedly low CO₂ flux rates and annual production distinguish the Everglades from many other wetlands. Nonetheless, impending changes in water management are likely to alter the CO₂ balance of this wetland and may increase the source strength of these extensive short-hydroperiod wetlands.