Carbon Cycling and Dissolved Organic Matter Export in the Northern Everglades
Because much of the Everglades is a vast subtropical freshwater fen, its carbon cycle can be expected to differ from that of most ecosystems in several important ways. The accumulation of peat is evidence that net primary productivity (NPP) exceeds heterotrophic respiration over the long term. The Everglades are subtropical, and thus NPP proceeds year-round, although with a peak in the summer (Davis 1989). Consequently, with a release from nutrient limitations, the potential rates of NPP may be expected to be high compared with many ecosystems. However, nutrient limitation by P is severe, and – like in many peat soils – the long-term storage of P has depleted the sources of recyclable P. In addition, the vast extent of contiguous peatland probably serves to minimize the impact of runoff from surrounding natural upland geological sources of mineral P. Acidity is not a factor in slowing the carbon cycle as is the case in acidic peatlands like the Okefenokee. The occurrence of an annual dry season and periodic droughts creates great episodic bursts of aerobic mineralization and conditions conducive to fires. The sapric nature of Everglades peat is likely a result of the subtropical warmth and periodic aerobic conditions. The low clay content and lack of an underlying clay layer also preclude the protection by organomineral complexes of the humified peat from decomposition when it is drained. Consequently, subsidence and the acceleration of respiration in the warm humid climate are exceptionally severe in the drained peats of the Everglades Agricultural Area (EAA). Finally, the relatively moderate concentrations of sulfate and presence of emergent species of macrophytes that vent methane to the atmosphere allow methane emission to be a prominent feature of the carbon cycle (Chanton et al. 1993).
KeywordsSoluble Organic Matter Dissolve Organic Carbon Concentration Dissolve Organic Matter Soil Pore Water South Florida Water Management District
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