[M-IS22] Biogeochemistry

[MIS22-12] Malate and manganese ion increase production of dissolved organic matter in acidic forest soils

*Kazumichi Fujii¹, Chie Hayakawa² (1.F-REI, 2.Utsunomiya Univ.)

Keywords:Soil, Forest, Dissolved organic carbon, Lignin

Lignin solubilization by exoenzymes is a key process driving the production of dissolved organic carbon (DOC) in acidic forest soils. Two potent ligninolytic enzymes are lignin peroxidase (LiP) commonly found in woody debris and manganese peroxidase (MnP) commonly found in organic soil layers. MnP activity requires manganese and chelating organic acids (esp., malate) for stabilizing Mn³⁺ to oxidize lignin. We test whether manganese and malate addition can increase DOC production by increasing MnP activity. We collected throughfall and soil solution leached from the organic layers and measured the concentrations of DOC in throughfall [A], DOC from the organic horizon [B], DOC from the organic horizon amended with manganese solution [C], DOC from the organic horizon amended with manganese and MnP and malate solution [D], DOC from the organic horizon amended with manganese and MnP and citrate solution [E], and DOC from the organic horizon amended with LiP [F]. DOC derived from native enzyme activity was calculated as B–A, DOC derived from MnP-malate combination was calculated as D–C, DOC derived from MnP-citrate combination was calculated as E–C, and DOC derived from LiP activity was calculated as F–C. Despite the same dose of organic acids, MnP-malate addition lead to significantly higher DOC concentrations, compared to MnP-citrate addition. MnP could produce DOC at the comparable levels with LiP addition. We found that manganese and malate addition can increase lignin solubilization by MnP and DOC production.