[A-CG39] Biogeochemical cycles in Land Ecosystem

[ACG39-P01] Factors of spatial variation in soil CH₄ uptake rate in forests in Western Honshu

*Munemasa Teramoto¹, Naishen Liang², Lifei Sun², Toshiaki Kondo³, Jun Koarashi⁴, Mariko Atarashi-Andoh⁴, Masahiro Takagi⁵, Norikazu Yamanaka¹, Takashi Hirano⁶, Kentaro Takagi⁶, Sachinobu Ishida⁷, Kazuhito Ichii⁸, Yoshiyuki Takahashi², Richa Hu¹ (1.Tottori University, 2.National Institute for Environmental Studies, 3.Japan International Research Center for Agricultural Sciences, 4.Japan Atomic Energy Agency, 5.University of Miyazaki, 6.Hokkaido University, 7.Hirosaki University, 8.Chiba University)

Keywords:Methane, Chamber, Soil moisture, Spatial variation, Volcanic ash soil

Forest soil is an important sink of atmospheric methane (CH₄) in natural terrestrial ecosystems. However, there is still large uncertainty for the spatial variation of CH₄ uptake rate in forest soils. In this study, we conducted field measurements for soil CH₄ flux and environmental parameters in forests in Western Honshu to examine the dominant factors for spatial variation of soil CH₄ uptake rate.

Measurements were conducted in late November in 2021 in five forest sites (a Japanese cedar forest site, a deciduous broad-leaved forest site, a beech forest site, a mixed forest site, and a red pine forest site) in research forests that belong to Tottori University. PVC collars (30 cm inner diameter, 4 cm depth, n = 15 to 20) were set in measurement points in each forest site one day before measurement. In those measurement points, we measured CH₄ flux using a portable automated chamber measurement system consisting of two cylindrical aluminum chambers (30 cm in diameter, 30 cm tall) and a control box. At the same time, soil temperature and soil moisture at the depth of 0-5 cm were also measured near each measurement point.

There were significant negative relationships between soil moisture and soil CH₄ uptake rate in the beech forest site and the red pine forest site. On the other hand, there was no significant relationship between soil moisture and soil CH₄ uptake rate in the Japanese cedar forest site, the deciduous broad-leaved forest site, and the mixed forest site. From those results, it was suggested that heterogeneity of surface soil moisture can partly explain the spatial variation of soil CH₄ uptake rate in some forest ecosystems, but we also need to consider other soil physicochemical and biological parameters for a better explanation for the variation.