JCSET | Watershed Studies Institute Research Symposium
Methane and Carbon Dioxide Dynamics of Stems and Soils in Bottomland Hardwood Forests of the Upper Mississippi Alluvial Valley
Academic Level at Time of Presentation
Graduate
Major
Biology, Watershed Science Concentration
List all Project Mentors & Advisor(s)
Jessica B. Moon, PhD
Presentation Format
Oral Presentation
Abstract/Description
Bottomland hardwood forests can hold large amounts of carbon in their tree biomass and their deep soil carbon pools. However, they can also produce a significant amount of methane (CH4) in their anaerobic soils. While some of this CH4 is oxidized in microsites and overlying waters, tree stems and exposed root systems are now known to be significant conduits of CH4 to the atmosphere, bypassing oxidation processes. We aim to contribute to this growing body of work, by identifying differences in CH4 source-sink dynamics among tree species (Acer rubrum, Liquidambar styraciflua, Taxodium distichum), across height on stems, and across stem hydrogeomorphic settings within bottomland hardwood wetlands of the upper Mississippi Alluvial Valley. Our initial study focused on soils and on stems of trees along 500 meters of floodplain and slough within the Clarks River National Wildlife Refuge. Our preliminary sampling during October 2022 focused on 12 stems of varying sizes across three species, five stem heights (i.e., 20, 40, 60, 120, and 180 cm), and adjacent soils. Measurements were averaged across two chambers per height across three dates during drought conditions. This sampling suggests that while the floodplain soils are sinks of methane, stems source methane with a significant difference between the stem and soil fluxes (p-value = 0.01, A. rubrum + L. styraciflua: p-value < 0.001). We also found no significant differences among species CH4 overall flux(p-value = 0.25), and there were no notable trends in CH4 efflux across trees of different size classes. Contrary to existing literature, we did not observe significant differences in CH4 fluxes between the various heights. Based on trends from this data, species behaved differently in terms of variation within flux; T. distichum significantly had the most variation in CH4 flux while A. rubrum significantly had the least. A. rubrum experienced significantly higher flux of CO2 than L. styraciflua. Source-sink dynamics per area of the floodplain will be dependent on collecting estimates of the tree surface area (currently being collected with 3D photogrammetry), and by developing relationships between stem height and CH4 flux rates. Our study will be essential to develop and validate tree stem CH4 schemes to improve land surface models for CH4 flux predictions.
Spring Scholars Week 2023 Event
Watershed Studies Institute Symposium
Methane and Carbon Dioxide Dynamics of Stems and Soils in Bottomland Hardwood Forests of the Upper Mississippi Alluvial Valley
Bottomland hardwood forests can hold large amounts of carbon in their tree biomass and their deep soil carbon pools. However, they can also produce a significant amount of methane (CH4) in their anaerobic soils. While some of this CH4 is oxidized in microsites and overlying waters, tree stems and exposed root systems are now known to be significant conduits of CH4 to the atmosphere, bypassing oxidation processes. We aim to contribute to this growing body of work, by identifying differences in CH4 source-sink dynamics among tree species (Acer rubrum, Liquidambar styraciflua, Taxodium distichum), across height on stems, and across stem hydrogeomorphic settings within bottomland hardwood wetlands of the upper Mississippi Alluvial Valley. Our initial study focused on soils and on stems of trees along 500 meters of floodplain and slough within the Clarks River National Wildlife Refuge. Our preliminary sampling during October 2022 focused on 12 stems of varying sizes across three species, five stem heights (i.e., 20, 40, 60, 120, and 180 cm), and adjacent soils. Measurements were averaged across two chambers per height across three dates during drought conditions. This sampling suggests that while the floodplain soils are sinks of methane, stems source methane with a significant difference between the stem and soil fluxes (p-value = 0.01, A. rubrum + L. styraciflua: p-value < 0.001). We also found no significant differences among species CH4 overall flux(p-value = 0.25), and there were no notable trends in CH4 efflux across trees of different size classes. Contrary to existing literature, we did not observe significant differences in CH4 fluxes between the various heights. Based on trends from this data, species behaved differently in terms of variation within flux; T. distichum significantly had the most variation in CH4 flux while A. rubrum significantly had the least. A. rubrum experienced significantly higher flux of CO2 than L. styraciflua. Source-sink dynamics per area of the floodplain will be dependent on collecting estimates of the tree surface area (currently being collected with 3D photogrammetry), and by developing relationships between stem height and CH4 flux rates. Our study will be essential to develop and validate tree stem CH4 schemes to improve land surface models for CH4 flux predictions.