Services provided by wetlands – is hydrology important?

We presented our latest wetlands research at the annual meeting of the South Atlantic Chapter of the Society of Wetlands Scientists. Wetlands provide many services, including groundwater recharge and flood mitigation, habitat for species adapted to life in seasonally wet environments, and recreational and even spiritual opportunities. Two biogeochemical services that wetlands provide are carbon and nitrogen storage, which mitigate greenhouse gas loading to the atmosphere and protect downstream water quality.

In this presentation, we asked: How important is wetland hydrology for these biogeochemical services? Depressional basin wetlands in the northern Tampa Bay region are flooded when the water table rises in response to the rainy season. Some wetlands, however, stay inundated for many months each years, whereas others generally fail to hold surface water. Soil inundation impedes decomposition of soil carbon by microorganisms, and soil carbon is an important substrate for “fueling” the immobilization of mineral nitrogen (the type in fertilizers and fallout from air pollution) in soil organic matter. We thus tested the prediction that well-inundated wetlands (compared with their highly-drained counterparts) would hold larger soil carbon pools and have a greater nitrogen immobilization capacity. We tested this prediction using a combination of isotopic (15N) labeling of soil, and long-term soil incubations. Our results were generally what we expected, but held a few surprises, too!