兵庫県氷ノ山のササ植生下にみられる土壌の母材の累積性と生成環境 Cumulative Property of the Soil Parent Materials and Soil Forming Environments under Bamboo-grass Vegetation on Mt. Hyono-sen, Hyogo Prefecture, Central Japan

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兵庫県の氷ノ山地域で,厚層多腐植質A層を持つ土壌を対象に,土壌母材の累積性と土壌の生成環境を調べた.その結果,土壌中の細砂の一次鉱物組成は,どの試料でもおおむねテフラ起源粒子と基岩の岩片とが混在するものであった.粘土・シルト画分の鉱物組成は,すべての試料で,基岩に由来する鉱物と風成塵などの外来物質とが混在するものであった.また,チシマザサ起源と考えられる植物珪酸体が多量に集積し,下層ほど風化が進んでいた.これらの結果から,この地域の厚層多腐植質A層を持つ土壌は,無機母材と有機物とが平衡して供給され,上方に発達した累積的な土壌であることが明らかになった.また土壌中の花粉分析の結果から,ササ植生は土壌生成開始期から長く維持され,現在ブナ林が成立している箇所でも,草原や疎林などの植生から次第に閉鎖した森林へと移り変わってきたと推定された.以上の諸点から,この地域の累積的な土壌の生成には,地形的安定性や冷涼な気候,母材としてのテフラ物質の存在のほかに,長期間にわたるササ植生の存在が強く影響していることが推察された.

Ando-soils with thick and humic A horizon derived from tephra materials are widely distributed in Japan. Recent studies are make it clear that these thick and humic A horizons have developed upward cumulatively. On the other hand, these soils are very sparsely distributed in the Kinki district of central Japan. One of the reasons may be that the parent material in this area are generally poor in tephra materials. In addition to the parent material factor, other factors, such as continuous supply of plentiful organic matter, topographic stability, and a suitable climate, may be necessary for the formation of a thick and humic A horizon.<br>To elucidate the pedogenetic processes, especially the cumulative properies of parent materials and the vegetational environments in the past, we researched Ando-like soils in Mt. Hyono-sen, Hyogo Prefecture. Three soil profiles are surveyed: one (H1) is located in a grassland of bamboo-grass (<i>Sasa kurilensis</i>); the other two profiles (H2, H3) in beech (<i>Fagus crenata</i>) forest with bamboo-grass as undergrowth. In addition to these soil samples, gravel of bedrock (andesite), peaty deposits in the vicinity, and volcanic glass were used as the mineralogical references. Microscopic mineral analysis for fine sand fraction and X-ray diffraction analysis for silt and clay fractions were carried out to investigate the origin of parent materials. Plant opal analysis and pollen analysis were used for the elucidation of past vegetational history.<br>Primary mineral composition of the fine sand fraction showed a mixture of tephra-origin particles (volcanic glass, hypersthene, hornblende) and bedrock-origin particles (groundmass fragments of andesite) in all horizons of each profile except the BC horizon of H1 profile. Mineralogy of silt and clay fractions also showed the mixed distribution of bedrockorigin minerals (feldspar, cristobalite) and foreign materials like eolian dust (quartz) in all horizons of each profile. A large number of plant opal grains have accumulated in each profile; most of them are considered to originate from bamboo-grass, and they were more strongly weathered in the deeper horizons. From these results, we conclude that the thick and humic A horizon in this area developed upward cumulatively under the balanced accumulation of organic matter and mineral materials. The results of pollen analysis suggested that bamboo-grass vegetation has been maintained for a long time, since the beginning of pedogenesis, and even the present beech forest has changed gradually from an open site with sparse forest or grassland to a closed forest. From the results mentioned above, it is inferred that the Ando-like soils in this area were formed under the strong influence of long-maintained bamboo-grass vegetation, as well as that of parent material and topographic and climatic factors.

収録刊行物

  • 第四紀研究  

    第四紀研究 35(4), 313-323, 1996-10-31 

    Japan Association for Quaternary Research

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各種コード

  • NII論文ID(NAID)
    10002634100
  • NII書誌ID(NCID)
    AN0034136X
  • 本文言語コード
    JPN
  • 資料種別
    ART
  • ISSN
    04182642
  • NDL 記事登録ID
    4076526
  • NDL 雑誌分類
    ZM49(科学技術--地球科学--地質)
  • NDL 請求記号
    Z15-67
  • データ提供元
    CJP書誌  CJP引用  NDL  J-STAGE 
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