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

本研究通过对寒温带森林湿地树干CH4通量的野外测量，阐明了控制湿地树干CH4排放速率的主要因素。我们还对树根的木材结构进行了解剖观察，以了解土壤携带的CH4在树体内可能的运输途径。研究区（0.12ha）水曲柳成熟树茎秆CH4排放速率在不同个体间差异较大，且呈现出明显的空间梯度，与地下水位的差异相对应。茎秆CH4排放率的季节变化幅度也存在较大的个体间差异。CH4排放率在24 h内相当稳定，落叶乔木的排放率也相当稳定。水曲柳成熟树细根皮层有发育良好的溶解性细胞间隙，即通气组织。

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.