PARENT SESSION
Contributed Oral Session 141: Restoration and Adaptive Management: Soils and Nutrients
Thursday, August 11, 1:30 PM - 5:00 PM, Meeting Room 520 C, Level 5, Palais des congrès de Montréal
Carbon sequestration and greenhouse gas emissions in natural and restored forested wetlands of the Lower Mississippi Valley.
Faulkner, Stephen*,1, Ullah, Sami2, 3, 1 U.S. Geological Survey, Lafayette, LA2 Louisiana State University, Baton Rouge, LA3 Current Address: Rutgers University, New Brunswick, NJ
ABSTRACT- Large-scale efforts are under way to offset rising CO2 emissions through terrestrial carbon sequestration. The conversion of over 75% of the riparian forests in the Lower Mississippi Valley (LMV) over the last two centuries, primarily to agriculture, has left large acreages available for reforestation. However, potential carbon sequestration gains may be offset by higher global warming potential associated with increased production of nitrous oxide (N2O)and methane (CH4), especially in agricultural watersheds. Relatively small changes in elevation can have significant effects on the biogeochemical processes that control carbon storage and the proportion of carbon and nitrogen exported as radiatively active reduced gases. We measured soil carbon storage and greenhouse gas emissions (N2O, CH4)in restored and natural forested wetlands across a range of soil types, age classes, and landscape positions in the LMV. Soil carbon content was highest in the natural riparian forests (2.74 ± 0.10 kg m-2) and lowest in a 23-year-old Quercus sp. plantation located on a ridge (0.74 ± 0.07 kg m-2). Similarly aged plantations in lower landscape positions had soil carbon contents comparable to the natural riparian forests. Landscape position also had a significant impact on greenhouse gas emissions with significantly higher N2O emissions from natural forests at lower elevation locations. The N2O:N2 emission ratio was significantly lower in natural forests (0.28) than cultivated soil in the same landscape position (0.64) and decreased rapidly in both systems as water-filled pore space increased from 70% to 100%. These results indicate that factors such as landscape position, hydrologic regime, and land use affect carbon storage and greenhouse gas emissions in the LMV. Simple estimates of carbon storage in vegetation and soil are not adequate to determine the influence of land management on net radiative forcing in floodplain ecosystems. Accurate estimates of the ability of reforestation in the LMV to offset global warming potential require a complete budget of both carbon sinks and greenhouse gas (N2O, CH4) emissions.
Key words: carbon sequestration, climate change, restoration, forested wetlands