Department of Physics
Portland State University
Current Research Areas
Emissions from rice agriculture
Role of trees in the methane budget
Methyl halide emissions from estuaries
Do trees emit methane? - Studying methane flux mediated by woody trees growing in anoxic sediments
Renewed interest in atmospheric methane has recently resulted from observations of larger than expected emissions in tropical forests and studies that upset the conventional wisdom by proposing that plants could produce methane in oxic environments. Both the mechanism and the magnitude of source estimations have been disputed in the literature. A few studies have suggested that woody tree systems could present a mechanism for transporting methane to the atmosphere from an anaerobic root zone under inundated conditions or, potentially, bypassing an aerobic oxidation layer that lies between deep roots and the atmosphere. These tree emissions could particularly enhance methane flux in tropical regions with regular seasonal inundation.
Results of a recent greenhouse study at PSU demonstrate the capacity for woody trees to transport methane from the rhizosphere to the atmosphere. Scaling emissions suggests that trees could present a sizeable global source of methane to the budget, plausibly as large as 60 Tg yr-1. This work was published in a issue of Geophysical Research Letters in 2010:
Rice, A.L., C.L. Butenhoff, M.J. Shearer, D. Teama, T.N. Rosenstiel, M.A.K. Khalil, Emissions of anaerobically produced methane by trees, Geophys. Res. Lett., 37, L03807, doi:10.1029/2009GL041565, 2010
and was covered by Nature news
Followup work investigated explored mechanisms of transport of methane through the species Populus trichocarpa in Biogeosciences Discussions in 2016: