Abstract
Abstract. There is increasing interest in the measurement of methane (CH4) emissions from tree stems in a wide range of ecosystems so as to determine how they contribute to the total ecosystem flux. To date, tree CH4 fluxes are commonly measured using rigid closed chambers (static or dynamic), which often pose challenges as these are bulky and limit measurement of CH4 fluxes to only a very narrow range of tree stem sizes and shapes. To overcome these challenges we aimed to design and test new semi-rigid stem-flux chambers (or sleeves). We compared the CH4 permeability of the new semi-rigid chambers with that of the traditional rigid chamber approach, in the laboratory and in the field, with continuous flow or syringe injections. We found that the semi-rigid chambers had reduced gas permeability and optimal stem gas exchange surface to total chamber volume ratio (Sc / Vtot) better headspace mixing, especially when connected in a dynamic mode to a continuous flow gas analyser. Semi-rigid sleeves can easily be constructed and transported in multiple sizes, are extremely light, cheap to build and fast to deploy. This makes them ideal for use in remote ecosystems where access logistics is complicated.
Highlights
Recent research into ecosystem greenhouse gas fluxes has shown that tree stems emit significant amounts of methane (CH4; Terazawa et al, 2007, 2015; Rusch and Rennenberg, 1998; Gauci et al, 2010; Pangala et al, 2013; Rice et al, 2010) the transport mechanisms and global importance of tree-mediated emissions remain largely unknown
The ratio between the gas exchange surface and the chamber volume (Sc / Vtot) was transposed from soil chambers and was not necessarily adapted to the lower fluxes found in tree stems, and are often too high (Hutchinson and Livingston, 2001)
In order to meet the new challenges presented by the growing interest in measuring greenhouse gas fluxes from tree stems we aimed to design, describe and test/deploy new semi-rigid stem-emission chambers in the laboratory and in the field, and to compare their permeability to CH4 with previously described rigid chambers
Summary
Recent research into ecosystem greenhouse gas fluxes has shown that tree stems emit significant amounts of methane (CH4; Terazawa et al, 2007, 2015; Rusch and Rennenberg, 1998; Gauci et al, 2010; Pangala et al, 2013; Rice et al, 2010) the transport mechanisms and global importance of tree-mediated emissions remain largely unknown These past investigations have used a variety of closed chambers adapted to various tree-stem sizes. If the chambers are too large for a given exchange surface, mixing problems may occur, making it important to circulate the air in their headspace (Hutchinson and Livingston, 1993; Rusch and Rennenberg, 1998)
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