Vertical distribution of organic matter, iron, phosphorus, and clay minerals accumulated in Ozegahara mire as a function of distance from rivers

尾瀬ヶ原湿原に流入・蓄積した無機成分の性状を明らかにするため，山ノ鼻，上田代，中田代において土壌・泥炭コアを採取して，強熱減量，遊離鉄含量，全リン酸含量，粒径組成，粘土鉱物組成を深度別に分析した．強熱減量は，表層付近では低層湿原や拠水林で低く，中間湿原，高層湿原，孤立林で高くなる傾向があった．ただし，深層では過去の流路や氾濫，火山噴出物などの影響を受け，その値は大きく変動する地点が多かった．遊離鉄含量は，表層付近で高くなる傾向があった．全リン酸含量は，深度との明瞭な関係性はなく，強熱減量の増加に対し放物線を描くような増減パターンを示し，湿原土壌中のリン酸の蓄積には河川からの距離と植物バイオマスによる吸収と蓄積が強く寄与していると考えられた．洪水などの河川氾濫の影響を強く受けたと思われる層位では、粒径組成において粗粒な画分割合が高かった．細粒画分（＜ 20μm）におけるX線回折分析の結果から，猫又川と川上川の河岸や山ノ鼻地区では上流の至仏山に分布する蛇紋岩由来の鉱物成分が顕著に検出された．一方，石英，クリストバライト，長石などの一次鉱物類は，地区によらず一様に堆積しており，風成 堆積の影響が強いことが示唆された．To clarify the properties of inorganic components that have flowed into and accumulated in Ozegahara mire, soil and peat core samples were collected in the Yamanohana-tashiro, Kamitashiro, and Nakatashiro and analyzed for ignition loss, free iron contents, total phosphate contents, particle size distribution, and clay mineral composition at different depths. The ignition loss near the surface layer tended to be lower in the low moors and higher in the middle and high moors, fragmented forest, gallery forests. In the deeper layers, however, there were many sites with large fluctuations due to the influence of past flow paths, flooding, and volcanic eruptions. The free iron content tended to be higher near the surface layer. The total phosphate content showed a parabolic pattern in response to the increase in the ignition loss, suggesting that the distance from the river and both of absorption and accumulation by plant biomass contribute strongly to the accumulation of phosphate in mire soils. A large proportion of coarse size fractions were found in layers that were strongly affected by past river flooding, regardless of the region. As for the fine fractions (< 20 μm), the results of X-ray diffraction analysis showed that the mineral components derived from serpentine distributed upstream (Mt. Shibutsu) were significantly detected in the banks of the Nekomata River and Kawakami River and in the Yamanohana-tashiro. On the other hand, primary minerals such as quartz, cristobalite, and feldspar were deposited regardless of the area, suggesting a strong influence of wind deposition