The Characteristics and Genesis of Volcanic Soils in Taiwan

摘要

Yangmingshan Volcanic National Park is the only park in Taiwan that has volcanic geography and hot springs. It mainly includes Mountains of Shamao, Chihsing, Tatun, Meintein, Chutzu, and Huangtzuei. The total area of the National Park is 11,455 ha. Volcanic activities were occurred at about from 0.5 to 0.8 million years ago, leaving the various signs of post-volcanic activity we can see today. The Pleistocene volcanic activities are most important in the geologic evolution of Taiwan. About 20 volcanoes are included in this volcano group. The Tatung andesite commonly contains augite, hornblende hypersthene or combinations of these materials. Until now, 86 soil pedons were studied in whole National park, major distributed in Mountains of Samao, Chishing, and Tatung. The soils were collected from different transects including Andisols (Hapludand, Fulvudand or in terms of Allophanic Andisols) and Inceptisols (Dystrudept, or in term of non-allophanic Andisols) are formed in different region of park. TheInceptisols almost distributed in the lower elevation and sharp landscape of the study area, about 60% of total area and the Andisols almost distributed in the higher elevation and stable landscape of the study area, about only 15% of the total area. The relationship between volcanic soil genesis and environmental factors is difficult to recognize in this area. We estimated that the interaction within climate, landscape and vegetation would be variable with time and reduced the effect of landscape on the volcanic soil genesis. Soil mapping can be conducted by the new techniques of selection of sampling transects, terrain analysis and GIS, and this technique is a useful, time efficient, and cost-effective tool to produce a reliable soil map in large area of park. Soil pedons selecting from Mt. Tatung to lower terrace were collected to understand the pedogenic process of volcanic soils and to identify the soil indicators of transition soils from Andisols to Ultisols under the same parent materials. Theresults of this study suggested that six pedogenesis indices may be useful to identify the transitional soils among of Andisols, Inceptisols, and Ultisols, including soil texture, soil consistence, bulk density, phosphate retention, and amorphous material content of Al_o+l/2Fe_o(%) and Si_o(%).