Estimation of sporadic CH4 emissions from a riparian wetland in responding to heave rain events

2023 Fiscal Year Final Research Report

• Project/Area Number: 21H03576
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 63010:Environmental dynamic analysis-related
• Research Institution: Kyoto University
• Principal Investigator: Kenshi Takahashi 京都大学, 生存圏研究所, 教授 (10303596)
• Co-Investigator(Kenkyū-buntansha): 東 若菜 神戸大学, 農学研究科, 助教 (20780761) ; 坂部 綾香 京都大学, 農学研究科, 助教 (40757936) ; 伊藤 雅之 兵庫県立大学, 環境人間学部, 准教授 (70456820)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: メタン / 湿地生態系 / フラックス / 短時間強雨 / レーザー計測

Outline of Final Research Achievements

We explored the mechanism of CH4 emission from the stem surfaces of Alnus japonica in a riparian wetland. CH4 emission rates were estimated using a closed-chamber method. Sap flux was measured using Granier-type thermal dissipation probes. Root anatomy was studied using both optical and cryo-SEM CH4 emissions during the leafy season exhibited a diurnally changing component superimposed upon an underlying continuum in which the diurnal variation was in phase with sap flux. We propose a model in which stem CH4 emission involves at least two processes: a sap flux-dependent component responsible for the diurnal changes, and a sap flux-independent component responsible for the background continuum. The background continuum possibly resulted from the diffusive transport of gaseous CH4 from the roots to the upper trunk. Root anatomy analysis indicated that the intercellular space of the cortex and empty xylem cells in fine roots could serve as a passageway for transporting gaseous CH4.

Free Research Field

大気環境学

Academic Significance and Societal Importance of the Research Achievements

メタンガスは二酸化炭素に次ぐ放射強制力を持つ重要な温室効果気体である．最近見つかったメタン発生源としての湿地性樹木に着目し，放出量を定量化するレーザー計測技術を開発するとともに，放出量の季節変動や気象要素に対する応答を明らかにした．大気中のメタンガス収支の精緻化に貢献する重要な成果である．