[M-IS14] 生物地球化学

[MIS14-04] 40年間の鉱物埋設実験が明らかにする初期土壌発達過程における母材および微生物群集の影響

*藤井 一至¹、眞中 卓也¹、早川 智恵²、和穎 朗太³ (1.森林総合研究所、2.宇都宮大学、3.農研機構)

キーワード：土壌、森林、炭素、鉱物風化

Soil develops through interaction of biotic (plant and microbes) and abiotic components (minerals). Importance of microbial necromass to formation of soil organic matter and aggregates has been well documented, while it is still unclear whether mineral type determines microbial community composition and pathway of soil development. Mineral powder samples [granite, basalt, andesite, sandstone, kaolinite, hydrohalloysite, Akahoya volcanic ash (7300 years old), Sakurajima volcanic ash (fresh)] in nylon mesh bags were buried in Southwest Japan (Okinawa and Amami islands) and recovered 0.5, 1.5, 10, 20, 40 years after burial. We measured changes in bulk density, C and N concentrations, pH, element composition, particle size distribution, specific surface area, microbial community diversity (Shannon, prokaryote and fungi), and 32 enzyme activities (Ecoplate). Soil pH and acid-neutralizing capacity (ANC) decreased with time for the respective mineral species, with the higher rates in granite and Sakurajima volcanic ash. No increases in clay contents were found, but increases in short-range-order minerals contributed to increases in C concentrations in volcanic ash and andesite. Microbial diversity increased with increasing soil C concentrations to reach saturation at the level close to the bulk soil. Enzyme activities increased with microbial diversity at the early two years, then they decreased with decreasing pH. We demonstrated that specific surface area of mineral species shape microbial diversity and that pH or ANC regulates decomposition activity and soil organic matte formation.