由土壤化育特徵探討珊瑚礁　海階面之地表作用　以恆春西台地為例

海岸地帶屬於變動快速區域，其地表作用複雜，而透過海階上覆土壤化育特徵的了解，將可以藉其為一指標，進而探討海階形成後所受的地表作用歷程。本研究觀察與分析了恆春西台地四個土壤樣本（HT-1a-1d），結果顯示無論是從剖面或是從微形態特徵，各土壤均具有黏聚層特徵且有較高的紅化程度，其中HT-1b和HT-1d具有多層序的特徵，顯示受到侵蝕-再積作用的影響；其次，各土壤B層黏粒含量最高約在33-40%，在pH值上，HT-1a和HT-1b酸度較大，HT-1c和HT-1d則呈弱酸到鹼性，各土壤表層的有機物分布在表層較多，而且各土壤中，鈣、鎂的含量則比較高，鹽基飽和度亦高（＞70%），惟各土壤的CEC值均在10 cmol(+) kg^(-1)以下，且游離鐵在B層含量多在25-28 g kg^(-1)之間，而結晶形態較差的無定形鐵含量甚低，又黏土礦物中高嶺石含量高，顯示各土壤有較高且相近的化育程度。大致上，四土壤樣體均可分類為典型老育濕潤極育土，並能以Simonson的增添、流失、位移與變質的化育機制模型來描述各土壤的化育作用，最後本研究以各土壤化育形態特徵與所經歷之化育作用為基礎，提出一土壤－地表作用假說，推論恆春西台地高位階地與土壤的關係及演育的過程。

關鍵字

地表作用；土壤化育特徵；海階；恆春西台地

並列摘要

Coastal landscapes undergo complex and rapidly changing geomorphic processes. Geomorphic processes and changes can be revealed by proxies of pedogenic features of soils overlaying the coastal reef-terraces. This study investigated and analyzed four soils (HT-1a-1d) on the highest reef-terraces of the West Hengchun Hills. Based on the micromorphologic profiles of four soils, this study identified features of the argillic horizon and higher rubifications. Two of the four soils (HT-1b and 1d) revealed poly-sequences indicated that they had been covered by re-depositional material eroded from the higher soils. Further analyses revealed high and similar pedogenicity of these four soils. Furthermore, properties of the soils suggest higher and similar pedogenic degrees. For example, the clay content in the Bt horizons of the soils was 33-40%, and the pH values were 5 to 7. Although the base saturation percentage exceeded 70% due to high Ca and Mg content, the cation exchangeable capacity (CEC) of the four soils was less than 10 cmol (+) kg^(-1). DCB extracted Fe in the Bt horizons of the soils were 25-28 g kg^(-1), but oxalate-oxalic acid extracted Fe were lower. The XRD revealed high amounts of kaolinite in the Bt horizons of the four soils. The soils could be classified as Typic Paleudults according to the Soil Taxonomy. The Simonsen model was used to analyze the pedogenic processes of the soils. Finally, based on the pedogenic processes and the parent materials of the four soils reported in an early study, a soil-geomorphic process model was developed for gauging the landform-surface evolution of the higher reef-terraces in the West Hengchun Hills.