title: Seasonal and snowmelt-driven changes in the water-extractable organic carbon dynamics in a cool-temperate Japanese forest soil, estimated using the bomb-(14)C tracer.
abstract: Water-extractable organic carbon (WEOC) in soil consists of a mobile and bioavailable portion of the dissolved organic carbon (DOC) pool. WEOC plays an important role in dynamics of soil organic carbon (SOC) and transport of radionuclides in forest soils. Although considerable research has been conducted on the importance of recent litter versus older soil organic matter as WEOC sources in forest soil, a more thorough evaluation of the temporal pattern of WEOC is necessary. We investigated the seasonal variation in WEOC in a Japanese cool-temperate beech forest soil by using the carbon isotopic composition ((14)C and (13)C) of WEOC as a tracer for the carbon sources. Our observations demonstrated that fresh leaf litter DOC significantly contributed to WEOC in May (35-52%) when the spring snowmelt occurred because of the high water flux and low temperature. In the rainy season, increases in the concentration of WEOC and the proportion of hydrophobic compounds were caused by high microbial activity under wetter conditions. From summer to autumn, the WEOC in the mineral soil horizons was also dominated by microbial release from SOC (>90%). These results indicate that the origin and dynamics of WEOC are strongly controlled by seasonal events such as the spring snowmelt and the rainy season's intense rainfall.
authors.affiliation: Research Group for Environmental Science, Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency, Ibaraki 319-1195, Japan. Electronic address: nakanishi.takahiro@jaea.go.jp.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Nakanishi
authors.affiliation: Research Group for Environmental Science, Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency, Ibaraki 319-1195, Japan.
authors.forename: Mariko
authors.initials: M
authors.lastname: Atarashi-Andoh
authors.affiliation: Research Group for Environmental Science, Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency, Ibaraki 319-1195, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Koarashi
authors.affiliation: Neotectonics Research Group, Geological Isolation Research and Development Directorate, Japan Atomic Energy Agency, Gifu 509-5102, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Saito-Kokubu
authors.affiliation: Tohoku Research Center, Forestry and Forest Products Research Institute, Iwate 020-0123, Japan.
authors.forename: Keizo
authors.initials: K
authors.lastname: Hirai
mesh_terms: D002244:Carbon / Q000032:analysis*; D057486:Carbon Cycle; D002247:Carbon Isotopes / Q000032:analysis; D017753:Ecosystem; D007564:Japan; D011834:Radiation Monitoring; D011891:Rain; D012621:Seasons; D012914:Snow; D012987:Soil / Q000737:chemistry*; D012990:Soil Pollutants, Radioactive / Q000032:analysis*
chemical_list: D002247:Carbon Isotopes; D012987:Soil; D012990:Soil Pollutants, Radioactive; D002244:Carbon
keywords: (13)C; (14)C; Carbon dynamics; Forest soil; Snowmelt; WEOC