[M-IS21_28PM2] Biogeochemistry

[MIS21-22] Mechanisms and regulating factors of dissolved organic matter production in beech forest soils in northern Kyoto

*Kazumichi FUJII¹, Yuji NAKADA², Makoto YOSHIDA², Chie HAYAKAWA³, Soh SUGIHARA³, Shinya FUNAKAWA³ (1.Forestry and Forest products Research Institute, 2.Tokyo University of Agriculture and Technology, 3.Kyoto University)

In forest ecosystems, most of the organic matter supplied to the organic layer mineralizes to CO₂, but a proportion (~30%) is leached as dissolved organic matter (DOM), as soil water percolates. DOM plays important roles in carbon and nutrient cycling in forest soils, however, the controlling factors and mechanisms of DOM production remain to be clarified. Since DOM contains high concentrations of aromatic compounds derived mainly from lignin, the roles of microorganisms in lignin solubilization and DOM production were investigated under field condition.The concentrations and fluxes of dissolved organic carbon (DOC) in soil solution were quantified under beech forest in northern Kyoto. The activities of lignin-degrading enzymes, lignin peroxidase (LiP) and manganese peroxidase (MnP), and fungal community composition were analyzed.The DOC fluxes increased in the organic layer (344 kg C ha^-1 yr^-1), followed by a decrease with depth in the mineral soil layers (20 kg C ha^-1 yr^-1). The seasonal fluctuation of DOC concentrations showed that DOC production increased in summer with increasing temperature, highlighting the importance of microbial activity to DOM production. The activities of both lignin-degrading enzymes, MnP and LiP, were detected in the organic layers, and several potential producers of enzymes, namely basidiomycete fungi, were also identified. These findings could support the central roles of fungi in lignin solubilization and DOC production in organic layers under beech forest in northern Kyoto, where the large fluxes of DOM leaching was observed.