Abstract：
The transport processes of methane (CH4 ) in tree stems remain largely unknown, although they are critical in assessing the whole-forest CH4 dynamics. We used a physically based dynamic model to study the spatial and diurnal dynamics of stem CH4 transport and fluxes. We parameterised the model using data from laboratory experiments with Pinus sylvestris and Betula pendula and compared the model to experimental data from a field study. Stem CH4 flux in laboratory and field conditions were explained by the axial advective CH4 transport from soil with xylem sap flow and the radial CH4 diffusion through the stem conditions. Diffusion resistance caused by the bark permeability did not significantly affect gas transport or stem CH4 flux in the laboratory experiments. The role of axial diffusion of CH4 in trees was unresolved and requires further studies. Due to the transit time of CH4 in the stem, the diurnal dynamics of stem CH4 fluxes can deviate markedly from the diurnal dynamics of sap flow.
摘要：
甲烷（CH4）在树干中的运输过程仍然未知，尽管它们在评估全林CH4动态方面至关重要。我们使用基于物理的动态模型来研究茎CH4运输和通量的空间和日动态。我们使用樟子松和Betulapendula的实验室实验数据对模型进行了参数化，并将模型与现场研究的实验数据进行了比较。实验室和田间条件下的茎CH4通量可通过木质部汁液从土壤中的轴向对流CH4运输和通过茎条件的径向CH4扩散来解释。在实验室实验中，由树皮渗透率引起的扩散阻力并未显着影响气体传输或茎CH4通量。CH4在树木中的轴向扩散作用尚未解决，需要进一步研究。由于CH4在茎中的运输时间，茎CH4通量的日动态可能明显偏离树液流的日动态。
