Carbon accumulation in natural and created wetlands

Background/Question/Methods Increasing levels of greenhouse gases are raising the awareness on climate change, and have created the necessity of finding effective ways to accumulate and store carbon to keep it form being released back to the atmosphere. Wetlands have an important role in global carbon cycles, as they are highly productive ecosystems that accumulate large amounts of organic matter in the soil, functioning as significant carbon sinks. The creation of wetlands to sequester carbon is considered a tool to abate climate change. The objective of this study is to determine the carbon sequestration rate of two similar riverine wetlands in Ohio, one natural and one created in 1994, to test the hypothesis that created wetlands can be as effective carbon sinks as natural ones. Soil cores were extracted in three different communities of both wetlands (open water, emergent, and edge) and analyzed for total carbon content to determine the wetland soil carbon pool. Sequestration rates were determined by radiometric dating with Cs-137 in the natural wetland, and by measuring accumulation over underlying non-hydric soil (prior to 1994) in the created one.

Results/Conclusions Both wetland soils are hydric with similar bulk densities (0.8 g cm^-3). Preliminary results indicate that the sediment accretion rate was higher in the created wetland (50 ton ha^-1yr^-1) than in the natural one (40 ton ha^-1yr^-1). Carbon content in the natural wetland was slightly higher than in the created wetland (54.2±1.22 gC kg^-1 (16) and 42.3±1.07 gC kg^-1 (12), respectively). The created wetland sequestered carbon at a faster rate (190 gC m^-2yr^-1) than did the natural one (142 gC m^-2yr^-1). These preliminary results indicate that, after 15 years, the created wetland is functioning as a sink for carbon and river sediments, and sequestering carbon more efficiently than the similar natural wetland studied. If created wetlands are successfully sequestering carbon, they can be used as cost-effective tools to abate the greenhouse effect of carbon emissions, while providing other important ecosystem services.