Methane Emissions from Estuarine Coastal Wetlands: Implications for Global Change Effect

Abstract

Core Ideas We investigated estuarine environmental factors on CH4 flux from two vegetation communities. Warming significantly affected on CH4 emission from the Phragmites australis community. There was a significant correlation between CH4 flux and water level in both communities. Salinity significantly affects CH4 emissions from the Phragmites australis community. The interaction between temperature and water level was the most important factor controlling CH4 flux. Global warming, rising sea levels, and saltwater intrusion interact to affect carbon cycling, specifically methane (CH4) flux in estuarine coastal wetlands. In the present study, Phragmites australis and Spartina alterniflora communities in the intertidal zone of the Yangtze estuary were selected for investigating CH4 flux under different temperature (natural/warming), water level (high/low), and salinity (0, 5, 15, and 30‰) conditions. The average CH4 flux (from April to October 2016) under natural conditions was 141.0 ± 21.5 and 502.8 ± 65.3 μmol m−2 h−1 for P. australis and S. alterniflora communities, respectively. Warming had a particularly pronounced effect on CH4 emissions from the P. australis community and increased CH4 flux by 130%. There was a significant correlation between CH4 flux and water level; at high water levels, CH4 flux was 2.64‐ and 3.78‐fold higher in P. australis and S. alterniflora communities, respectively. Salinity had a significant pronounced effect on CH4 emissions from the P. australis community, and there was a clear order (5‰ > 15‰ > 0‰ > 30‰) in CH4 flux. The interaction between temperature and water level was the most important factor controlling CH4 flux from wetlands; CH4 emissions were greater at higher temperature and higher water levels. However, at low water level, the effect of salinity was more prominent. The results suggest that CH4 flux from estuarine wetlands could be further enhanced in the future under the influence of rising sea levels due to global warming.

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

“…This follows prior field, mesocosm, and incubation studies across a variety of wetlands, in which temperature has been shown to be a strong predictor of CH4 emissions (e.g. Al-Haj and Fulweiler, 2020;van Bodegom and Stams, 1999;Christensen et al, 2003;Dise et al, 1993;Fey and Conrad, 2000;Liu et al, 2019;Ward et al, 2013;Yang et al, 2019;Yvon-Durocher et al, 2014) and in which plant functional type has an interacting effect (Chen et al, 2017;Duval & Radu, 2018;L. Liu et al, 2019;Mueller et al, in press;Ward et al, 2013).…”

“…CC BY 4.0 License. functional groups and CH4 emissions have been demonstrated through field studies in other wetland ecosystems such as peatlands (Bubier et al, 1995;Ward et al, 2013) (Bubier et al, 1995, Ward et al, 2013) and in tidal wetland mesocosms (L. Liu et al, 2019;Martin & Moseman-Valtierra, 2017;Mueller et al, in press). We provide field evidence that two species with distinct plant traits --Schoenoplectus and Spartina --have strikingly different effects on CH4 emissions from brackish wetlands.…”

“…However, this effect could be mitigated if these high-elevation Spartina marshes become dominated by Schoenoplectus in response to predicted accelerated sea-level rise (Kirwan & Guntenspergen, 2012). In addition, Spartina traits are plastic and influenced by factors such as soil redox conditions (Kludze & DeLaune, 1994), salinity (Crozier & DeLaune, 1996), and water level (Liu et al, 2019), all of which can be expected to change plant-mediated effects on CH4 biogeochemistry. Further studies are needed to thoroughly assess the range of https://doi.org/10.5194/bg-2020-376 Preprint.…”

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

“…Measurements of Schoenoplectus, Spartina, and Distichlis biomass were conducted during peak biomass of each year (29 July-2 August) as described by Noyce et al (2019). Schoenoplectus biomass was estimated using non-destructive allometric techniques (Lu et al, 2016) in 900 cm 2 quadrats, and Spartina and Distichlis biomass were estimated through destructive harvest of 25 cm 2 subplots.…”

A Structured Approach for the Mitigation of Natural Methane Emissions—Lessons Learned from Anthropogenic Emissions

“…Recent research point to largely underestimated methane emissions from oil and gas production questioning also the lower GHG emission factor of natural gas [16]. Furthermore, models predict a strong increase of natural emissions such as from permafrost [17][18][19].…”