Modeling impacts of changes in temperature and water table on C gas fluxes in an Alaskan peatland

Authors

Jia Deng, University of New Hampshire - Main CampusFollow
Changsheng Li, University of New Hampshire - Main CampusFollow
Steve Frolking, University of New Hampshire - Main CampusFollow

Abstract

Northern peatlands have accumulated a large amount of organic carbon (C) in their thick peat profile. Climate change and associated variations in soil environments are expected to have significant impacts on the C balance of these ecosystems, but the magnitude is still highly uncertain. Verifying and understanding the influences of changes in environmental factors on C gas fluxes in biogeochemical models are essential for forecasting feedbacks between C gas fluxes and climate change. In this study, we applied a biogeochemical model, DeNitrification-DeComposition (DNDC), to assess impacts of air temperature (T_A) and water table (WT) on C gas fluxes in an Alaskan peatland. DNDC was validated against field measurements of net ecosystem exchange of CO₂ (NEE) and CH₄ fluxes under manipulated surface soil temperature and WT conditions in a moderate rich fen. The validation demonstrates that DNDC was able to capture the observed impacts of the manipulations in soil environments on C gas fluxes. To investigate responses of C gas fluxes to changes in T_A and soil water condition, we conducted a series of simulations with varying T_A and WT. The results demonstrate that (1) uptake rates of CO₂ at the site were reduced by either too colder or warmer temperatures and generally increased with increasing soil moisture; (2) CH₄ emissions showed an increasing trend as T_Aincreased or WT rose toward the peat surface; and (3) the site could shift from a net greenhouse gas (GHG) sink into a net GHG source under some warm and/or dry conditions. A sensitivity analysis evaluated the relative importance of T_A and WT to C gas fluxes. The results indicate that both T_A and WT played important roles in regulating NEE and CH₄ emissions and that within the investigated ranges of the variations in T_A and WT, changes in WT showed a greater impact than changes in T_A on NEE, CH₄ fluxes, and net C gas fluxes at the study fen.

Department

Earth Sciences, Earth Systems Research Center

Publication Date

7-2015

Journal Title

Journal of Geophysical Research Biogeosciences

Publisher

Wiley

Digital Object Identifier (DOI)

10.1002/2014JG002880

Document Type

Article

Recommended Citation

Deng, J., C. Li, and S. Frolking (2015), Modeling impacts of changes in temperature and water table on C gas fluxes in an Alaskan peatland, J. Geophys. Res. Biogeosci., 120, 1279–1295, doi:10.1002/2014JG002880.

Rights

©2015. American Geophysical Union. All Rights Reserved.