化育自變質岩與火成岩母質的台灣紅壤性質

Abstract

選擇三個育自蛇紋岩、安山岩及玄武岩的台灣紅壤，探討其形態、理化性質、礦物種類及分類地位，結果發現母質及時間爲三個土壤樣體化育的主要控制因子。三個土壤樣體的粘粒含量在A到Bt化育層間顯箸增加，在關山系及出衛系Bt化 育層均能發现粘粒膜，可是粘粒膜只發現於淡水系底層上壤，主要因淡水系所受風化作用最劇烈。強烈的風化作用最劇烈。強烈的風化作用，使關山系及淡水系土壤pH值偏低，東衛系土壤則因東北季風帶來細顆粒珊瑚粒子於表層，而呈鹼性反應。赤鐵礦爲土壤中主要的氧化鐵礦物；層狀矽酸鹽粘土礦物以高嶺石爲主，且含量隨土壤深度增加而減少，但是只有淡水系土壤因其CEC值小於24 cmol(+)/kg clay，符合低活性粘粒土壤性質。根據美國土壤分類系統，關山系、淡水系及東衛系分別分類爲粘質、混合、炎熱的典型喑紅潤淋餘土，粘質、混合、炎熱的極台簡潤淋餘土及粘質、混合、炎熱的典型過育乾熱淋餘土。 Three well-drained red soil profiles derived from serpentine, andesite, and basalt materials were selected to study their characteristics. We found that different parent materials and time control significantly their pedogenic ways. In Ks and Btw soil series whose parent materials were mainly serpentine and basalt rocks, an increase in clay content from topsoil to B horizon and existence of clay skins was observed in all Bt horizons; however, clay skins were only found in the lower Bt horizon for Ts soil series from andesite due to the destroy of clay skins under more and longer strongly weathering conditions. Since the weathering state is high throughout the pedons. Ks and Ts soil series were acidic. The higher pH of surface soil for the Btw soil series was due to the addition of fine coraJ particles carried by northeastern monsoon. Hematite was the most abundant Fe oxide mineral in these soils. Kaolinite was the dominant layer silicate mineral and its content decreased with depth. Only Ts soil series was qualified as low activity clay soil due to its CEC less than 24 cmol(+)/kg clay. According to Soil Taxonomy, Ks, Ts, and Btw soil series were classified as clayey, mixed, hyperthermic Typic Rhodudalfs, clayey, mixed, hyperthermic Ultic Hapludalfs, and clayey, mixed, hyperthermic Typic Paleustalfs, respectively.