Methane in stems of living and dead trees
|代表者||EPRON Daniel (Kyoto University, Graduate School of Agriculture)|
|共同研究者||TAKAHASHI Kenshi (Kyoto University, RISH)
SAKABE Ayaka (Kyoto University, Graduate School of Agriculture)
NISHIMURA Hiroshi (Kyoto University, RISH)
DANNOURA Masako (Kyoto University, Graduate School of Agriculture)
ASAKAWA Susumu (Nagoya University, Graduate School of Bioagricultural Sciences)
Forests are a well-known carbon sink, which mitigate the rise in atmospheric carbon dioxide and hence global warming. However, methane emissions by stems of living trees become a major concern due to the increasing contribution of methane to global warming. Indeed, methane is the second most important anthropogenic greenhouse gas. Until now, global and regional methane budgets of forests, which cover one third of the land area on Earth (67 % in Japan) have only considered the source and sink functions of soils, ignoring stem emissions. The role of trees, in addition to that of the soil, must be considered in the methane budget of forests. This requires a more mechanistic understanding of transport and production processes in tree stems because the current lack of knowledge hampers any effort to model and upscale methane dynamics.
There are now evidences that trees emit methane through their stems. In addition, microbial communities in heartwood of trees can be an important but overlooked internal source of methane. The scientific question we wish to answer is whether the stems of living and dead trees are passive conduits through which the methane produced in the soil is transferred or whether the stems harbor methanogenic archaea that produce methane internally.
To answer this question, we will develop a method to measure methane concentration within the stem of trees, which, when used in combination with a stem chamber to trace methane emission, will allow us to distinguish between transport and internal production. We will characterize stem anatomical features (tissue porosity) which influence both the axial and the radial diffusion of stem gases. We will begin to test the hypothesis that stems of some trees are home to a microbial community comprising methanogenic archaea while other accumulate soluble phenolic compounds that would act as antibiotic substances against methanogenic microbes.