Biogeochemical and anatomical studies on the mechanisms of tree-mediated methane emissions in forested wetland ecosystems

为明确寒温带森林湿地树干CH4排放速率的主要控制因素，我们对树干CH4排放通量进行了野外观测。此外，我们还对树根的木材结构与土壤中CH4在树体中可能的运输途径进行了解剖学观察。在一个研究地点(0.12公顷)内，成熟水曲柳树干的CH4释放速率在个体之间差异很大，并显示出明显对应于该地点地下水位深度差异的空间梯度。在树干甲烷排放速率的季节变化幅度上也观察到了很大的个体间差异。在整个24小时内，有叶树和落叶树的CH4排放速率相当稳定。成熟水曲柳细根的皮层有发达的溶生性细胞间隙，即透气组织。

We performed field measurements of CH4 fluxes at tree stems to clarify the major controlling factors of stem CH4 emission rates in cool-temperate forested wetlands. We also conducted anatomical observations of wood structure of tree roots in relation to the possible transport pathway of soil-borne CH4 in a tree body.CH4 emission rates from stems of mature Fraxinus mandshurica trees varied greatly among individuals within a study site (0.12ha), and showed a spatial gradient apparently corresponding to the difference in water table depth in the site. Large inter-individual differences were also observed in the magnitude of seasonal changes in stem CH4 emission rate. CH4 emission rates were quite stable throughout a 24 h period for foliated trees and similarly for defoliated trees. Well-developed lysigenous intercellular spaces, i.e., aerenchyma tissues, were observed at the cortex of fine roots of mature Fraxinus mandshurica trees.