Eddy covariance based methane flux in Sundarbans mangroves, India

Abstract

We report the initial results of the methane flux measured using eddy covariance method during summer months from the world's largest mangrove ecosystem, Sundarbans of India. Mangrove ecosystems are known sources for methane (CH 4) having very high global warming potential. In order to quantify the methane flux in mangroves, an eddy covariance flux tower was recently erected in the largest unpolluted and undisturbed mangrove ecosystem in Sundarbans (India). The tower is equipped with eddy covariance flux tower instruments to continuously measure methane fluxes besides the mass and energy fluxes. This paper presents the preliminary results of methane flux variations during summer months (i.e., April and May 2012) in Sundarbans mangrove ecosystem. The mean concentrations of CH 4 emission over the study period was 1682 ± 956 ppb. The measured CH 4 fluxes computed from eddy covariance technique showed that the study area acts as a net source for CH 4 with daily mean flux of 150.22 ± 248.87 mg m −2 day −1. The methane emission as well as its flux showed very high variability diurnally. Though the environmental conditions controlling methane emission is not yet fully understood, an attempt has been made in the present study to analyse the relationships of methane efflux with tidal activity. This present study is part of Indian Space Research Organisation-Geosphere Biosphere Program (ISRO-GBP) initiative under 'National Carbon Project'.

Are methane emissions from mangrove stems a cryptic carbon loss pathway? Insights from a catastrophic forest mortality

“…Although large uncertainties exist within our upscaled results due to our study representing small-scale temporal resolution, our measurements and estimates of both dead and living mangrove stem CH 4 flux should be considered as highly conservative for both this system and (especially) other tropical mangrove systems. This is because (1) the tree density of the tropical-arid Australia Gulf region are about two-thirds lower than systems of similar latitudes (Sanders et al, 2016); (2) we could only account for dry season (tropical) winter sampling (where methanogen microbial metabolism may be lower) which have been shown to have the lowest seasonal sedimentary CH 4 fluxes (Chauhan et al, 2008;Allen et al, 2011); (3) we could not account for diurnal and high tide sampling, which has been shown to emit c. 80% higher CH 4 fluxes during high tides from the Sundarban mangroves (Jha et al, 2014); (4) we could not account for branched trees which in some cases may substantially increase the flux per tree estimate; (5) fluxes were only scaled to 2 m in height; and (6) downed tree fluxes were not measured.…”

Seasonal Variations of Carbon Dioxide, Water Vapor and Energy Fluxes in Tropical Indian Mangroves

“…The tower is surrounded by a continuous mangrove patch with dominant species viz. Avicennia alba, Bruguiera gymnorrhiza, Rhizophora, with a mean canopy height of about 5 m [23].…”

“…One of the main objectives of NCP is to establish a network of EC flux towers in different representative forest ecosystems in the Indian subcontinent to understand their CO 2 source and sink strengths [23][24][25]. As part of this, an eddy covariance flux tower was established in mangrove forests in the Sundarbans Biosphere Reserve in April 2012 and has been taking measurements since then.…”

Eddy covariance for quantifying trace gas fluxes from soils

“…Only very recently have researchers started to also extend eddy covariance measurements to ever more challenging and less widespread ecosystem types, such as mangroves Jha et al, 2014), deserts (Honrath et al, 2002;Liu et al, 2012;Li et al, 2014), intertidal flats (Polsenaere et al, 2012), and screenhouses (Tanny et al, 2006).…”