Biogeochemical and plant trait mechanisms drive enhanced methane emissions in response to whole-ecosystem warming

Noyce, Genevieve L.; Megonigal, J. Patrick

doi:10.5194/bg-18-2449-2021

Cited by 29 publications

(24 citation statements)

References 85 publications

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“…For belowground productivity, root ingrowth cores were installed in November 2018 and removed a year later, after which the dry weight of fine roots in the core was determined. Methane emissions were measured as described in Noyce and Megonigal (2021) using static chambers and a Los Gatos Research Ultraportable Greenhouse Gas Analyzer. Water level was derived from one water level sensor (AquaTROLL 200) located in each plant community, which was then corrected to water level above marsh surface (m) using three averaged RTK elevation measurements from each plot.…”

Section: Methodsmentioning

confidence: 99%

Temperature optimum for marsh resilience and carbon accumulation revealed in a whole‐ecosystem warming experiment

Smith

Noyce

Megonigal

et al. 2022

Global Change Biology

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Coastal marshes are globally important, carbon dense ecosystems simultaneously maintained and threatened by sea‐level rise. Warming temperatures may increase wetland plant productivity and organic matter accumulation, but temperature‐modulated feedbacks between productivity and decomposition make it difficult to assess how wetlands and their thick, organic‐rich soils will respond to climate warming. Here, we actively increased aboveground plant‐surface and belowground soil temperatures in two marsh plant communities, and found that a moderate amount of warming (1.7°C above ambient temperatures) consistently maximized root growth, marsh elevation gain, and belowground carbon accumulation. Marsh elevation loss observed at higher temperatures was associated with increased carbon mineralization and increased microtopographic heterogeneity, a potential early warning signal of marsh drowning. Maximized elevation and belowground carbon accumulation for moderate warming scenarios uniquely suggest linkages between metabolic theory of individuals and landscape‐scale ecosystem resilience and function, but our work indicates nonpermanent benefits as global temperatures continue to rise.

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Section: Methodsmentioning

confidence: 99%

Temperature optimum for marsh resilience and carbon accumulation revealed in a whole‐ecosystem warming experiment

Smith

Noyce

Megonigal

et al. 2022

Global Change Biology

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“…We cannot distinguish among these mechanisms with the present dataset. Sulfate depletion was a better indicator of CH 4 flux than salinity or SO 4 2concentration alone and may prove to be a superior proxy for CH 4 emissions in tidal brackish marshes (Keller et al 2009;Noyce and Megonigal 2021).…”

Section: Discussionmentioning

confidence: 93%

“…Differences in methane emissions between dominant vegetation communities have been observed in tidal marsh systems such as Phragmites australis versus S. alterniflora (Yuan et al 2015), P. australis versus mixed and native zones (Mueller et al 2016) and S. patens versus Schoenoplectus americanus (Noyce and Megonigal 2021); however, such differences are not always observed (Emery and Fulweiler 2014). Plant species composition affects CH 4 emissions through several mechanisms (Koebsch et al 2013;Moor et al 2017;Mueller et al 2020).…”

Section: Introductionmentioning

confidence: 99%

Vegetation and hydrology stratification as proxies to estimate methane emission from tidal marshes

et al. 2021

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Direct measurement of methane emissions is cost-prohibitive for greenhouse gas offset projects, necessitating the development of alternative accounting methods such as proxies. Salinity is a useful proxy for tidal marsh CH4 emissions when comparing across a wide range of salinity regimes but does not adequately explain variation in brackish and freshwater regimes, where variation in emissions is large. We sought to improve upon the salinity proxy in a marsh complex on Deal Island Peninsula, Maryland, USA by comparing emissions from four strata differing in hydrology and plant community composition. Mean CH4 chamber-collected emissions measured as mg CH4 m−2 h−1 ranked as S. alterniflora (1.2 ± 0.3) ≫ High-elevation J. roemerianus (0.4 ± 0.06) > Low-elevation J. roemerianus (0.3 ± 0.07) = S. patens (0.1 ± 0.01). Sulfate depletion generally reflected the same pattern with significantly greater depletion in the S. alterniflora stratum (61 ± 4%) than in the S. patens stratum (1 ± 9%) with the J. roemerianus strata falling in between. We attribute the high CH4 emissions in the S. alterniflora stratum to sulfate depletion likely driven by limited connectivity to tidal waters. Low CH4 emissions in the S. patens stratum are attributed to lower water levels, higher levels of ferric iron, and shallow rooting depth. Moderate CH4 emissions from the J. roemerianus strata were likely due to plant traits that favor CH4 oxidation over CH4 production. Hydrology and plant community composition have significant potential as proxies to estimate CH4 emissions at the site scale.

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“…Methane fluxes from salt marshes vary between elevation zones due to changes in soil properties, plant species composition, plant traits and rhizosphere characteristics (Burke et al 2002, Philippot et al 2009, Noyce and Megonigal 2021, Rosentreter et al 2021. The soil properties affecting CH 4 emissions include temperature, bulk density, redox conditions, hydrological regime and substrate supply (Boeckx et al 1997, Zhao et al 2020, Noyce and Megonigal 2021, Rosentreter et al 2021. Salinity (as a proxy for sulphate supply from tidal floodwaters) is a major control (Mitsch andGosselink 2007, Poffenbarger et al 2011) and sulphate-reducing bacteria in the soil outcompete methanogenic archaea .…”

Section: Introductionmentioning

confidence: 99%

Spartina alterniflora has the highest methane emissions in a St. Lawrence estuary salt marsh

Comer‐Warner

Ullah

Reyes

et al. 2022

Environ. Res.: Ecology

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Salt marshes have the ability to store large amounts of ‘blue carbon’, potentially mitigating some of the effects of climate change. Salt marsh carbon storage may be partially offset by emissions of CH4, a highly potent greenhouse gas (GHG). Sea level rise and invasive vegetation may cause shifts between different elevation and vegetation zones in salt marsh ecosystems. Elevation zones have distinct soil properties, plant traits and rhizosphere characteristics, which affect CH4 fluxes. We investigated differences in CH4 emissions between four elevation zones (mudflat, Spartina alterniflora, Spartina patens and invasive Phragmites australis) typical of salt marshes in the northern Northwest Atlantic. CH4 emissions were significantly higher from the S. alterniflora zone (17.7±9.7 mg C m-2 hr-1) compared to the other three zones, where emissions were negligible (< 0.3 mg C m-2 hr-1). These emissions were high for salt marshes and were similar to those typically found in oligohaline marshes with lower salinities. CH4 fluxes were significantly correlated with soil properties (salinity, water table depth (WTD), bulk density and temperature), plant traits (rhizome volume and biomass, root volume and dead biomass volume all at 0-15 cm) and CO2 fluxes. The relationships between CH4 emissions, and rhizome and root volume suggest that the aerenchyma tissues in these plants may be a major transport mechanism of CH4 from anoxic soils to the atmosphere. This may have major implications for the mitigation potential carbon sink from salt marshes globally, especially as S. alterniflora is widespread. This study shows CH4 fluxes can vary over orders of magnitude from different vegetation in the same system, therefore, specific emissions factors may need to be used in future climate models and for more accurate carbon budgeting depending on vegetation type.

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Biogeochemical and plant trait mechanisms drive enhanced methane emissions in response to whole-ecosystem warming

Cited by 29 publications

References 85 publications

Temperature optimum for marsh resilience and carbon accumulation revealed in a whole‐ecosystem warming experiment

Temperature optimum for marsh resilience and carbon accumulation revealed in a whole‐ecosystem warming experiment

Vegetation and hydrology stratification as proxies to estimate methane emission from tidal marshes

Spartina alterniflora has the highest methane emissions in a St. Lawrence estuary salt marsh

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