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Amazon floodplain ecosystems include open water and intermittent flood forest and agricultural systems with different water types. They are a significant natural source of methane (CH4) in the tropics. When soils are flooded and become anoxic, CH4 is produced by methanogenesis, while microbially mediated aerobic and anaerobic oxidation of CH4 serves as the primary biological sink of this greenhouse gas. Measurements of rates and controls on CH4 production and emission in the Amazon basin mainly come from studies on individual wetlands and floodplain lakes. Similarly, microbial communities in those Amazon floodplain habitats have been studied on individual lakes based on sequence-specific DNA analysis. Existing biogeochemical ecosystem models of CH4 from the Amazon floodplains focus on soil properties or involve factors such as pH, redox potentials, or substrates. None of these models incorporate appropriate seasonal inundation; neither the microbiota does it as a component. In this sense, our chapter will highlight how the important efforts already contributed to understand the CH4 emission and its connections with abiotic and biotic factors in Amazon floodplains, as well as emphasize the need of encouraging cooperation and exchange of experience between research teams by using different approaches and scientific methods."
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This content will become publicly available on December 13, 2025
Quantifying Gross Rates of Methane Production and Consumption in a Northern Forest
Northern forest soils are vital for climate change mitigation since upland sandy soils favor the net consumption/oxidation of atmospheric methane (CH4). We are studying biogeochemical CH4 cycle processes in a Northern Forest (Howland Research Forest, Maine), where upland soils are interspersed with wetland (Sphagnum bog), and upland-wetland transition soils along with hummock-hollow microtopography. This complex mosaic of microsites with sources and sinks of CH4 is subjected to change under future wet climates projected for this region, with a potential for these forests to shift from a net CH4 sink to a net CH4 source. Net CH4 emissions in a wet climate can increase either by inhibiting methanotrophs or favoring methanogens, or both. Thus, quantifying underlying processes of gross CH4 production and consumption can reduce the uncertainty of CH4 sink/source estimation in this critical ecosystem. We have collected baseline soil data across the forest's landscape including Total Carbon and Total Nitrogen with the Elemental Analyzer, Gravimetric Soil Moisture, and pH. Furthermore, stable isotope dilution method will serve as a proxy for methanogenic and methanotrophic activities to quantify gross rates of CH4 production and consumption from a flooding (wet-up) experiment in Howland Forest. We will differentiate between CH4 consumption and production by measuring both the change in the amount of CH4 and the ratio between labeled and unlabeled CH4 in a closed system. We will analyze the stable C isotope in 13CH4 to determine gross rates of CH4 production and oxidation in situ and within laboratory incubations. The in situ stable isotope dilution technique will be compared with the gas push-pull method, to test the suitability of a simple, low cost method to quantify gross CH4 oxidation rates. Novel data obtained in this study will constrain CH4 cycle processes in a biogeochemical model to quantify CH4 source-sink potential in Northern Forests under current and future climatic conditions.
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- PAR ID:
- 10645559
- Publisher / Repository:
- American Geophysical Union
- Date Published:
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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