Methane Dynamics of Vegetation-Soil Interactions in Bald Cypress and Other Bottomland Hardwood Forests
Authors
Bassil El Masri1* (belmasri@murraystate.edu), Skylar, Ross1, Marissa Miles1, Jarred Asselta2, Jessica Moon1, Gary Stinchcomb3, Kabi Raj Khatiwada4, Benjamin R.K. Runkle4
Institutions
1Murray State University, Murray, KY; 2University of Minnesota–Twin Cities, Minneapolis/St. Paul, MN; 3University of Memphis, Memphis, TN; 4University of Arkansas, Fayetteville, AR
Abstract
Methane (CH4) is one of the most important greenhouse gases and more than 30% of its total emissions originate from wetlands. There is high uncertainty in the contribution of mineral soil wetlands to global CH4 budgets. The project objectives are (1) to improve the understanding of the controls on CH4 fluxes in forested mineral soil wetlands; and (2) to better understand the effects of landscape position and forest composition on the CH4 fluxes between terrestrial ecosystems and the atmosphere. Using a coupled modeling-experimental approach, researchers are measuring the spatial and temporal dynamics of CH4 fluxes in soils and woody structures (stems and knees) of temperate bald cypress (Taxodium distichum) and other bottomland hardwood stands and incorporating measurements into an ecosystem model to improve the model representation and predictions of CH4 fluxes. Soil collars and custom-built chambers were installed in the stems and knees of trees along four sites that span a hydrologic gradient from the terrace to the stream channel in western Kentucky’s Clarks River National Wildlife Refuge (CRNWR). The team found significant differences in soil CH4 fluxes (p-value < 0.02) between the bald cypress stand and the other species stands (p-value < 0.02), but no significant differences in stem CH4 fluxes among species (p-value = 0.25) during the drought year. These results showed a higher average soil CH4 uptake rate in high knee density areas compared to no knee areas (p = 0.004) that can offset the observed knee CH4 emission. Researchers found no statistically significant difference between soil fluxes during drought and after historic flooding events (except for the postoak site), but the flooding event can enhance stem and knee CH4 emissions. The team will use ongoing monitoring to improve understanding of soil-vegetation interaction in hardwood bottomland wetlands and incorporate these functions into ongoing processes-based modeling efforts.