| Summary: | 碩士 === 國立臺灣大學 === 農業化學研究所 === 102 === Tatun Volcano Group was major active volcano in Taiwan. Volcanic soils are always classified as Andisols based on Soil Taxonomy. Andisols were transformated to Inceptisols or Ultisols with decreasing the elevation of the Yangminshan National Park. Shamaoshan (Sms) and Dinghuoxiu (Dhx) mountain are both belong to Tatun Volcano Group. Sms soil is relative younger (0.3 Ma) and mainly affected by parent material and Dhx soil is relatively old (0.79 Ma) and mainly affected by time and climate. The objectives of this study of two region volcanic soils with different pedogenic processes time are (1) to integrate soil morphological characteristics and chemical analysis to identify the soil properties and soil classification, and (2) to investigate the pedogenic processes with weathering time. Total six pedons were sampled from Sms and Dhx regions. Soil characteristics include soil morphology, physical and chemical properties, showed that the major differences of pedogenic processes were major affected by different weathering time. In this study, all Sms pedons had thiner soil depth (<100 cm), black soil color with high organic matter, granular soil structure and friable consistence. All Dhx pedons had thicker soil depth (>250 cm), brown color, subangular or angular blocky soil structure and firm consistence. Sms pedons were classified as Andisols with andic soil properties. Sms-Summit, and Sms-Backslope-2 pedons with melanic epipedon and it can be classified as Typic Melanudand based on Soil Taxonomy, however Sms-Backslope-1 pedons without melanic epipedon was classified as Typic Hapludands. Dhx pedons had longer weathering time and stronger leaching processes to show the soils without the andic soil properties. Soil classification of Dhx soils was affected by the landscape positions. Dhx pedon with the elevation higher than 300 meters above sea level (asl) had the characters of thick argillic horizon and low base saturation, which can be classified as Paleudults. Dhx pedon with the elevation lower than 300 meters above sea level had cambic horizon without andic soil properties, which can be classified as Andic Dystrudepts. An weathering time gap was found between Sms and Dhx pedons that resulting in significantly different andic soil characteristics, according to pedogenic processes and soil weathering time, the pedogenic processes of soils of two volcanic region are time dependent and shown as the soil formation sequence as: Andisols, Andic Inceptisols, Inceptisols, and finally Ultisols. Prolonged weathering has a significant effect on pedogenic processes, but the morphology and elevation are the main factors of detailed soil classification.
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