While wetlands are the largest natural source of methane (CH4 ) to the atmosphere, they represent a large source of uncertainty in the global CH4 budget due to the complex biogeochemical controls on CH4 dynamics. Here we present, to our knowledge, the first multi-site synthesis of how predictors of CH4 fluxes (FCH4) in freshwater wetlands vary across wetland types at diel, multiday (synoptic), and seasonal time scales. In this work we used several statistical approaches (correlation analysis, generalized additive modeling, mutual information, and random forests) in a wavelet-based multi-resolution framework to assess the importance of environmental predictors, nonlinearities and lags on FCH4 across 23 eddy covariance sites. Seasonally, soil and air temperature were dominant predictors of FCH4 at sites with smaller seasonal variation in water table depth (WTD). In contrast, WTD was the dominant predictor for wetlands with smaller variations in temperature (e.g., seasonal tropical/subtropical wetlands). Changes in seasonal FCH4 lagged fluctuations in WTD by ~17 ± 11 days, and lagged air and soil temperature by median values of 8 ± 16 and 5 ± 15 days, respectively. Temperature and WTD were also dominant predictors at the multiday scale. Atmospheric pressure (PA) was another important multiday scale predictor for peat-dominated sites, with drops in PA coinciding with synchronous releases of CH4. At the diel scale, synchronous relationships with latent heat flux and vapor pressure deficit suggest that physical processes controlling evaporation and boundary layer mixing exert similar controls on CH4 volatilization, and suggest the influence of pressurized ventilation in aerenchymatous vegetation. In addition, 1- to 4-h lagged relationships with ecosystem photosynthesis indicate recent carbon substrates, such as root exudates, may also control FCH4. By addressing issues of scale, asynchrony, and nonlinearity, this work improves understanding of the predictors and timing of wetland FCH4 that can inform future studies and models, and help constrain wetland CH4 emissions.
Knox, Sara H., et al. "Identifying dominant environmental predictors of freshwater wetland methane fluxes across diurnal to seasonal time scales." Global Change Biology, vol. 27, no. 15, Apr. 2021. https://doi.org/10.1111/gcb.15661
Knox, Sara H., Bansal, Sheel, McNicol, Gavin, et al., "Identifying dominant environmental predictors of freshwater wetland methane fluxes across diurnal to seasonal time scales," Global Change Biology 27, no. 15 (2021), https://doi.org/10.1111/gcb.15661
@article{osti_1844532,
author = {Knox, Sara H. and Bansal, Sheel and McNicol, Gavin and Schafer, Karina and Sturtevant, Cove and Ueyama, Masahito and Valach, Alex C. and Baldocchi, Dennis and Delwiche, Kyle and Desai, Ankur R. and others},
title = {Identifying dominant environmental predictors of freshwater wetland methane fluxes across diurnal to seasonal time scales},
annote = {While wetlands are the largest natural source of methane (CH4 ) to the atmosphere, they represent a large source of uncertainty in the global CH4 budget due to the complex biogeochemical controls on CH4 dynamics. Here we present, to our knowledge, the first multi-site synthesis of how predictors of CH4 fluxes (FCH4) in freshwater wetlands vary across wetland types at diel, multiday (synoptic), and seasonal time scales. In this work we used several statistical approaches (correlation analysis, generalized additive modeling, mutual information, and random forests) in a wavelet-based multi-resolution framework to assess the importance of environmental predictors, nonlinearities and lags on FCH4 across 23 eddy covariance sites. Seasonally, soil and air temperature were dominant predictors of FCH4 at sites with smaller seasonal variation in water table depth (WTD). In contrast, WTD was the dominant predictor for wetlands with smaller variations in temperature (e.g., seasonal tropical/subtropical wetlands). Changes in seasonal FCH4 lagged fluctuations in WTD by ~17 ± 11 days, and lagged air and soil temperature by median values of 8 ± 16 and 5 ± 15 days, respectively. Temperature and WTD were also dominant predictors at the multiday scale. Atmospheric pressure (PA) was another important multiday scale predictor for peat-dominated sites, with drops in PA coinciding with synchronous releases of CH4. At the diel scale, synchronous relationships with latent heat flux and vapor pressure deficit suggest that physical processes controlling evaporation and boundary layer mixing exert similar controls on CH4 volatilization, and suggest the influence of pressurized ventilation in aerenchymatous vegetation. In addition, 1- to 4-h lagged relationships with ecosystem photosynthesis indicate recent carbon substrates, such as root exudates, may also control FCH4. By addressing issues of scale, asynchrony, and nonlinearity, this work improves understanding of the predictors and timing of wetland FCH4 that can inform future studies and models, and help constrain wetland CH4 emissions.},
doi = {10.1111/gcb.15661},
url = {https://www.osti.gov/biblio/1844532},
journal = {Global Change Biology},
issn = {ISSN 1354-1013},
number = {15},
volume = {27},
place = {United States},
publisher = {Wiley},
year = {2021},
month = {04}}
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Biological and Environmental Research (BER); National Science Foundation (NSF); Arctic Challenge for Sustainability II (ArCS II); Japan Society for the Promotion of Science (JSPS); National Research Foundation of Korea (NRF); California Department of Fish and Wildlife; USDA; National Institute of Food and Agriculture (NIFA); Canada Research Chairs Program; Canada Foundation for Innovation (CFI); Natural Sciences and Engineering Research Council of Canada (NSERC); National Aeronautics and Space Administration (NASA); Ohio Department of Natural Resources; Academy of Finland; Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning; Kempe Foundation; German Federal Ministry of Food and Agriculture (BMEL); European Union’s Horizon 2020; USGS; Svenska Forskningsrådet Formas
Grant/Contract Number:
AC02-05CH11231; SC0021067
OSTI ID:
1844532
Alternate ID(s):
OSTI ID: 1785295
Journal Information:
Global Change Biology, Journal Name: Global Change Biology Journal Issue: 15 Vol. 27; ISSN 1354-1013
Vourlitis, George; Dalmagro, Higo; De S. Nogueira, Jose
FluxNet; California State University, San Marcos; Universidade de Cuiabá; Universidade Federal de Mato Grosso; University of British Columbiahttps://doi.org/10.18140/flx/1669368