(第24號)臺灣省紅棕壤生成之綜合研究

Abstract

本報告綜合紅棕壤生成之理論，檢討過去本省紅棕壤調查及研究事實與近年來研究之進展，分從紅棕壤本身之特徵，討論其生成，茲摘要於下： （一）綜合過去文獻，紅棕壤之生成，包括磚紅土化作用與灰土化作用，生成於揚潤之熱帶或亞熱帶氣候與植物，尤以有顯明之乾濕季節與良好之排水環境下發育完善，至於母質則過去之文獻並無嚴格之規定，惟1960年美國第七次土壤分類草案，則認為Rhodochrults昔稱紅棕壤者，其生成母質為鹽基性火成岩；徜母岩鹽基減少則列入Typochrults，即昔稱紅黃色灰化土者，亦有謂磚紅化土壤之母質，多係上新世至中新世風化之遺物。 （二）紅棕壤之特徵：(1)物理性方面，七色用Munsell標準土色咭以規範之，色譜可由紅至棕，潤時色值少於4的質地B層，乾時色值較潤時不致大一單位以上。(2)化學性方面，粘粒部分之Sa或ki值為1.33~2.00，游離鐵Fe2O3超10%，Al層之有機質低於4%，B層具低鹽基飽和度＜35%。（3）礦物性方面，磚紅土化土壤之粘土曠物成分以kaolinite為主，Gibbsite與Fe2O3亦與焉；由灰土化作用生成較顯之紅棕壤與黃色灰化土，其枯土礦物成分，除Koalitrite為主要成分外，Vermiculite與Gibbsite占次要成分，山水成母質生成之剖面，則B層下並無Gibbsite發見，至於Illite係存在於中間性的黃色灰化土中。 This report includes the general review on the theories of the formation of Reddish Brown Latosols and some evidence being found during the period when soil survey and recent studies concerning the particular subject. In view of these general findings, the genesis of Reddish Brown Latosols is clarified. It may be summarized as follow: 1. From the previous reports it is learned that the genesis of Reddish Brown Latosols includes laterization and podzolization. The Reddish Brown. Latosols are found in humid climates ranging from cool-temperate to the tropics or subtropics regions. Apparently dry and wet alternate seasons. are much favorable to the formation. There is no strict limit for the parent material being recorded the in past literature, but the parent materials is confessed by the 7th approximation of soil classification U. S. D. A. 1960. As Rhodochrults which have been called Reddish Brown Latosols are primarily basic igneous rocks. they grade into Typochrults which have been called Red-yellow podzolic soils if the parent rocks become less basic. The parent material of the Reddish Brown Latosois was also called the weathering residual product of the Pliocene and Miocene age.