title: The contribution of trees to ecosystem methane emissions in a temperate forested wetland.
abstract: Wetland-adapted trees are known to transport soil-produced methane (CH4), an important greenhouse gas to the atmosphere, yet seasonal variations and controls on the magnitude of tree-mediated CH4emissions remain unknown for mature forests. We examined the spatial and temporal variability in stem CH4emissions in situ and their controls in two wetland-adapted tree species (Alnus glutinosa and Betula pubescens) located in a temperate forested wetland. Soil and herbaceous plant-mediated CH4emissions from hollows and hummocks also were measured, thus enabling an estimate of contributions from each pathway to total ecosystem flux. Stem CH4emissions varied significantly between the two tree species, with Alnus glutinosa displaying minimal seasonal variations, while substantial seasonal variations were observed in Betula pubescens. Trees from each species emitted similar quantities of CH4from their stems regardless of whether they were situated in hollows or hummocks. Soil temperature and pore-water CH4concentrations best explained annual variability in stem emissions, while wood-specific density and pore-water CH4concentrations best accounted for between-species variations in stem CH4emission. Our study demonstrates that tree-mediated CH4emissions contribute up to 27% of seasonal ecosystem CH4flux in temperate forested wetland, with the largest relative contributions occurring in spring and winter. Tree-mediated CH4emissions currently are not included in trace gas budgets of forested wetland. Further work is required to quantify and integrate this transport pathway into CH4inventories and process-based models.
authors: 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.
authors: Sunitha R
authors: SR
authors: Pangala
authors: School of Earth Sciences, Bristol Biogeochemistry Research Centre & Cabot Institute, University of Bristol, Will Memorial Building, Queen's Road, Bristol, BS8 1RJ, UK.
authors: Edward R C
authors: ERC
authors: Hornibrook
authors: 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.
authors: David J
authors: DJ
authors: Gowing
authors: 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.
authors: Vincent
authors: V
authors: Gauci
keywords: 
  Alnus glutinosa
  ; 
  Betula pubescens
  ; methane; seasonal variation; stem CH4 emissions; tree-mediated CH4 emissions; wetlands