Spectral evidence for substrate availability rather than environmental control of methane emissions from a coastal forested wetland

Mitra, Bhaskar; Minick, Kevan J.; Miao, Guofang; Domec, Jean‐Christophe; Prajapati, Prajaya; McNulty, Steven G.; Sun, Ge; King, John S.; Noormets, Asko

doi:10.1016/j.agrformet.2020.108062

Cited by 26 publications

(15 citation statements)

References 89 publications

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“…At four sites, maximum IR was between GPP or NEP and FCH4, suggesting that recent photosynthates may also control FCH4 at the diel scale (Table 1), with a lag on the order of 1–4 h (Figure 8). These lags are comparable to other studies which found that GPP caused a diurnal pattern in CH 4 emissions (Hatala, Detto, & Baldocchi, 2012; Knox et al, 2016; Mitra et al, 2020). However, in some cases where GPP was identified as a dominant predictor of FCH4 at the diel scale, GPP seemed to modulate the amplitude of the diel pattern rather than the shape of the diel pattern in FCH4 (Figure S11).…”

Section: Discussionsupporting

confidence: 90%

“…At the seasonal scale, FCH4 lagged both LE (17 ± 18 days) and GPP (~13 ± 23 days) considerably. These lags reflect the fact that GPP and LE peaked before FCH4, similar to the findings of Delwiche et al (in press) and Mitra et al (2020). At the seasonal scale, this lag suggests a delay between labile organic carbon inputs from plants (either in the form of exudates or fresh detritus) and FCH4 (Megonigal et al, 2004).…”

Section: Discussionsupporting

confidence: 87%

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Identifying dominant environmental predictors of freshwater wetland methane fluxes across diurnal to seasonal time scales

Knox

Bansal

McNicol

et al. 2021

Global Change Biology

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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. 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.

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Section: Discussionsupporting

confidence: 90%

Section: Discussionsupporting

confidence: 87%

Identifying dominant environmental predictors of freshwater wetland methane fluxes across diurnal to seasonal time scales

Knox

Bansal

McNicol

et al. 2021

Global Change Biology

View full text Add to dashboard Cite

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“…Two biological factors, Ecosystem Respiration (RECO) and plant Gross Primary Production (GPP), also exerted strong controls on daily F CH4 in bog, fen, and marsh wetlands. These strong relationships between F CH4 and vegetation carbon turnover are consistent with the findings of many previous studies (Hatala et al, 2012a;Mitra et al, 2020;Rinne et al, 2018). Plant GPP stimulates CH 4 production indirectly by providing carbon input, mainly via root exudates fueling microbial activity, which produces substrates (such as acetate and CO 2 ) for acetotrophic and hydrogenotrophic methanogenesis (Bastviken, 2009;Mitra et al, 2020;Ström et al, 2012;Whiting and Chanton, 1993).…”

Section: Causal Relationships Derived From Transfer Entropysupporting

confidence: 90%

Causality Guided Machine Learning Model on Wetland Ch4 Emissions Across Global Wetlands

Yuan¹,

Zhu²,

Li³

et al. 2022

SSRN Journal

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“…Mitra et al. (2020) also found the most significant variance in F CH4 occurred at the diel scale in a coastal forested wetland in North Carolina. While the variability of F CH4 peaked at 365 days, little variation occurred for the frequency between 90 and 364 days (Figure 2c).…”

Section: Resultsmentioning

confidence: 99%

“…The variability at the diel scale accounted for 57% of F CH4 variations, followed by seasonal (25%) and multiday scales (18%) (Figure 2). Mitra et al (2020) also found the most significant variance in F CH4 occurred at the diel scale in a coastal forested wetland in North Carolina. While the variability of F CH4 peaked at 365 days, little variation occurred for the frequency between 90 and 364 days (Figure 2c).…”

Section: Multiscale Variability Of F Ch4 and Its Biophysical Driversmentioning

confidence: 99%

Biophysical Controls of Ecosystem‐Scale Methane Fluxes From a Subtropical Estuarine Mangrove: Multiscale, Nonlinearity, Asynchrony and Causality

Liu

Valach

Baldocchi

et al. 2022

Global Biogeochemical Cycles

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Mangroves are complex ecosystems subject to periodic and irregular changes in meteorology, tides, water quality and biological factors. Methane dynamics in mangroves and their dependence on biogeochemical controls across scales are poorly characterized using traditional parametric statistics. We measured the ecosystem‐scale methane flux (FCH4) using an eddy covariance system in a subtropical estuarine mangrove for two years. A combination of nonparametric statistical approaches, including singular spectrum analysis and information theory, was used to isolate multiscale FCH4 variations and explore their variability and dominant controls at different time scales. FCH4 exhibited the largest variability at the diel scale (57%), followed by seasonal (25%) and multiday (18%) scales. Mutual information metrics suggested that variation in FCH4 was dominantly coupled to plant activities through synchronous processes at the diel scale. Moreover, fluctuations in atmospheric turbulence and soil temperature dominated multiday variation in FCH4 through asynchronous processes. Seasonally, soil temperature and water salinity were dominant variables leading to changes in FCH4 with a time lag of 12 and 17 days, respectively. Weak links between FCH4 and tidal heights were found across all the studied time scales. Transfer entropy metrics indicated that a super typhoon event substantially weakened causal links between biophysical variables and FCH4 by causing severe defoliation and disturbing the soil microbial community. The typhoon also temporarily decoupled the causal link between FCH4 and temperature. These findings call for the inclusion of the properties of scale emergence, nonlinearity, asynchrony and causality for comprehensively understanding and accurately predicting the interactions between mangrove FCH4 and its biophysical controls.

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Spectral evidence for substrate availability rather than environmental control of methane emissions from a coastal forested wetland

Cited by 26 publications

References 89 publications

Identifying dominant environmental predictors of freshwater wetland methane fluxes across diurnal to seasonal time scales

Identifying dominant environmental predictors of freshwater wetland methane fluxes across diurnal to seasonal time scales

Causality Guided Machine Learning Model on Wetland Ch4 Emissions Across Global Wetlands

Biophysical Controls of Ecosystem‐Scale Methane Fluxes From a Subtropical Estuarine Mangrove: Multiscale, Nonlinearity, Asynchrony and Causality

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