Controls on methane emissions from Alnus glutinosa saplings.
Recent studies have confirmed significant tree-mediated methane emissions in wetlands; however, conditions and processes controlling such emissions are unclear. Here we identify factors that control the emission of methane from Alnus glutinosa. Methane fluxes from the soil surface, tree stem surfaces, leaf surfaces and whole mesocosms, pore water methane concentrations and physiological factors (assimilation rate, stomatal conductance and transpiration) were measured from 4-yr old A. glutinosa trees grown under two artificially controlled water-table positions. Up to 64% of methane emitted from the high water-table mesocosms was transported to the atmosphere through A. glutinosa. Stem emissions from 2 to 22 cm above the soil surface accounted for up to 42% of total tree-mediated methane emissions. Methane emissions were not detected from leaves and no relationship existed between leaf surface area and rates of tree-mediated methane emissions. Tree stem methane flux strength was controlled by the amount of methane dissolved in pore water and the density of stem lenticels. Our data show that stem surfaces dominate methane egress from A. glutinosa, suggesting that leaf area index is not a suitable approach for scaling tree-mediated methane emissions from all types of forested wetland.
Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR), Department of Environment, Earth and Ecosystems, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK.
Sunitha R
SR
Pangala
Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR), Department of Environment, Earth and Ecosystems, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK.
David J
DJ
Gowing
School of Earth Sciences, Bristol Biogeochemistry Research Centre & Cabot Institute, University of Bristol, Will Memorial Building, Queen's Road, Bristol, BS8 1RJ, UK.
Edward R C
ERC
Hornibrook
Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR), Department of Environment, Earth and Ecosystems, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK.
Vincent
V
Gauci
D029661:Alnus / Q000737:chemistry*; D060587:Groundwater; D008697:Methane / Q000032:analysis*; D018547:Plant Stems / Q000737:chemistry; D014197:Trees / Q000737:chemistry*; D014835:Volatilization; D053833:Wetlands
D008697:Methane
Alnus glutinosa; lenticels; methane (CH4); stem CH4 emissions; tree-mediated methane emissions; wetland