Submitted to: Catena
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2007
Publication Date: 1/1/2008
Citation: Phillips, R.L., Beeri, O. 2008. The Role of Hydropedologic Vegetation Zones in Greenhouse Gas Emissions for Agricultural Wetland Landscapes. Catena 72:386-394. Interpretive Summary: Soil gas emissions in agricultural wetland landscapes have not been quantified in the northern prairie and spatial variability associated with vegetation communities may influence gas emissions. Soil traces gas emissions such as carbon dioxide, methane, and nitrous oxide are important components to the carbon budget. Higher emissions increase the net greenhouse effect and reduce carbon sequestration potential. We found spatial variability in trace gas emissions were associated with plant communities surrounding water bodies and with upland land-use. We used a new satellite-based method for detecting plant communities to stratify a landscape and to scale up data collected for basins surrounded by rangeland and cropland. Results indicated the croplands emitted the greatest proportion of greenhouse gases on July 12, while the deep marsh vegetation (nearest to the open water) emitted the greatest proportion on August 3. This study demonstrates the importance of spatial variability in calculating the net greenhouse effect and how carbon credit information may be scaled up using new remote-sensing based tools.
Technical Abstract: Net greenhouse gas (GHG) source strength for agricultural wetland ecosystems in the Prairie Pothole Region (PPR) and spatial constraints associated with CH4, CO2, and N2O fluxes are currently unknown. Greenhouse gas fluxes typically vary with edaphic, hydrologic, biologic, and climatic factors. In the PPR, characteristic wetland plant communities integrate hydropedologic factors and may explain some variability associated with trace gas fluxes at ecosystem, and potentially landscape, scales. We addressed this question for replicate wetland basins located in central North Dakota stratified by previously established soil-plant-water (hydropedologic) zone on 12 July and 3 August 2003. Data were collected at the soil-atmosphere interface for deep marsh, shallow marsh, wet meadow, low prairie, pasture, and cropland soils. Controlling for soil moisture and temperature, CH4 fluxes varied significantly with zone (p< 0.0131). Highest CH4 emissions were found near the water in the deep marsh (277.76 mg CH4 m-2 d-1) and declined with distance from water to -0.73 mg CH4 m-2 d-1 in the pasture. Carbon dioxide fluxes also varied significantly with zone. Nitrous oxide variability was greater within zones than between zones, with no significant effects of zone, moisture, or temperature. Data were extrapolated for a 205.63 km2 landscape using a previously developed synoptic classification for PPR plant communities. For this landscape, we found croplands contributed the greatest proportion to the net GHG source strength on July 12 (45,700 kg GHG-C equivalents d-1) while deep marsh zones contributed the greatest proportion on August 3 (26,145 kg GHG-C equivalents d-1). The overall landscape average for each date, weighted by zone, was 462.36 kg GHG-C equivalents km-2 d-1 on July 12 and 314.28 kg GHG-C equivalents km-2 d-1 on August 3. Results suggest hydropedologic vegetation zones are keystone to greenhouse gas fluxes at the soil-atmosphere interface in agricultural wetland landscapes, particularly for CH4.