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Biophysical processes and feedback mechanisms controlling the methane budget of an Amazonian peatland

Active Dates 9/1/2019-2/29/2024
Program Area Terrestrial Ecosystem Science
Project Description
Problem Statement: Tropical peatlands are a major methane (CH4) source and represent an important biophysical feedback factor acting on Earth’s radiative forcing. There is evidence in recent years for an increase in global CH4 mixing ratios (> 6.7 ppb per year from 2009 to 2017) with a pronounced increase in equatorial zones. Global top-down and carbon-13 isotope analyses suggest that this increasing trend has largely been driven by changes in natural biogenic sources in response to warmer and wetter tropical conditions. However, large uncertainties in these source estimates persist because of a lack of CH4 observations in the tropics, and it is difficult to rule out other factors such as increased anthropogenic emissions or reductions in CH4 sink activity. Furthermore, the largest expanses of tropical peatlands are located in lowland areas of Southeast Asia, the Congo Basin, and the Amazon Basin where observations are sparse. The Loreto Province of Amazonian Peru is comprised of about 36,000 km2 of peatlands, however, the extent of these low elevation peatlands has only recently been documented and little is known about their biogeochemistry and ecophysiology. Our proposed research, therefore, aims to address these knowledge gaps by providing much needed data regarding the biogeochemistry of CH4 cycling in tropical Amazonian peatlands and developing and testing an Earth System Model that can be used to forecast how hydrometeorological variations and changes in peatland structure in tropical regions will influence the CH4 budget of the atmosphere. Here, we propose to use the United States Department of Energy’s Energy Exascale Earth System Model (E3SM) land surface component (ELM) in a synergistic fashion with field experiments and modeling activities mutually informing new scientific understanding.
A. Evaluate and modify algorithms within the ELM land surface model to improve its ability to simulate CH4 production and consumption in tropical peatlands and assess potential feedbacks acting between hydrometeorological forcings and the carbon balance of these neotropical peatlands;
B. Determine the magnitude of the inter-annual variability of the CH4 and CO2 budgets and examine how hydrometeorological and ecophysiological factors influence these budgets;
C. Assess how much CH4 is produced and transported to the atmosphere via living and dead trees compared to the diffusive flux from peat soil and ebullition events;
D. Examine the importance of anaerobic oxidation of methane (AOM) in determining the CH4 budget and evaluate its representation in ELM;
E. Determine how photosynthetic and respiratory activity varies through time and space and how they influence the CO2 and CH4 budgets at short (hourly) to inter-annual timescales.
Potential Impact: The proposed field experiments and modeling activities will advance scientific understanding of biogeochemical cycling dynamics in Amazonian peatlands and the representation of these ecosystems within an Earth System Modeling framework. The experimental and modeling activities will be synergistic and inform one another to reduce the uncertainty regarding future CH4 emissions and feedbacks to climate in a region where CH4 cycling is hypothesized to be highly sensitive to climate. The modeling activities will provide new insights regarding CH4 emissions for an ensemble of plausible climate change scenarios for the region over the time period 2020 to 2080.

Award Recipient(s)
  • University of Minnesota (PI: Griffis, Timothy)
  • USDA Forest Service, North Central Forest Experiment Station (NCFES) (PI: Lilleskov, Erik)