八卦臺地北部階地土壤化育及其在地形對比之應用
Other Title
Pedogenesis of Soils and their Applications of Correlations to Terraces in Northern Pakua Tableland, Central Taiwan
Journal
地理學報
Journal Issue
61
Start Page
123
End Page
145
ISSN
0494-5387
Date Issued
2011
Author(s)
Abstract
定年資訊的不足，將使得河階研究產生許多限制，惟近年以土壤化育的觀點，應用在階地對比與地形演育等議題上，已在八卦臺地南部階地群等地區獲得良好的成果。因此，進一步探討八卦臺地北部階地土壤化育程度，將有助階地土壤的化育特性，並檢討八卦臺地過去的階地對比成果。本研究在八卦臺地橫山以北五個階面各選擇一代表性土壤剖面進行分析，結果顯示各樣體紅化程度高，具有強度的亞稜塊或稜塊構造，黏性、塑性、緊密與堅硬程度均佳，質地為黏土或坋質黏土，裡土層可觀察到黏粒膜；其次，各樣體具有強酸性、低鹽基飽和度、高黏粒含量及低CEC/clay比值等特性，並富含鐵氧化物，且鐵結晶比率多在40%以上，另黏土礦物組成除有蛭石、伊萊石、石英外，還有高嶺石和水鋁氧等，顯示各樣體化育程度極高。在美國土壤分類系統中，屬於簡育濕潤氧化物土，如以整個八卦臺地南部與北部階地土壤而言，則可在此階地土壤間建立弱育土－極育土－氧化物土的時間序列特性。不過，本研究五個樣體間仍可辨識出些微的化育差異，例如以化育層指數(horizon index, HI)值與加權土壤剖面化育指數(weighted profile development index, WPDI)值比較，可發現銀行山(PKN-1a)、南風寮(PKN-1b)、六分寮(PKN-1c)等樣體之值略高於豆周寮(PKN-2a)與施厝坪(PKN-2b)，而與八卦臺地南部階地土壤比較則可將PKN-1a、1b、1c和PK-1所屬的橫山面對比為同一階，而PKN-2a、2b和PK-2所代表之埔中面亦為相同時期階地。本研究的對比結果，大略支持了前人研究的看法，惟對於其中銀行山面的劃分有異。
The lack of dating information has resulted in limitations in the study of river terraces in Taiwan; however, in recent years the pedogenesis of soils in southern Pakua terraces has constructed a chronosequence for correlating terraces. As earlier studies based on the geomorphic model require additional supporting evidence, the sampling of soils from terraces in northern Pakua tableland will help in revealing its pedogenic sequence, as well as the correlation between terraces in the Pakua tableland. Soils (labeled as PKN-1a, PKN-1b, PKN-1c, PKN-2a and PKN-2b) from the terraces north of the Hengshan, the highest geomorphic surface in terms of altitude, were sampled and analyzed. Additional data from six soil pedons from southern Pakua tableland were cited from Tsai et al. (2006) for comparison. Based on well-developed morphologies and other chemical properties, these soils, classified as Typic Hapludox according to USDA Soil Taxonomy, have been highly weathered, having undergone prolonged soil development. Moreover, we have proposed a Inceptisol-Ultisol-Oxisol chronosequence of soils in all Pakua terraces. Therefore, PKN-1a, PKN-1b and PKN-1c have similar degrees of soil development, and are hypothesized to be correlated with PK-1 of the southern tableland. PKN-2a and PKN-2b have equal degrees of soil development, and can be correlated with PK-2 from the southern tableland. In addition to the terrace of PKN-1a, the correlation based on pedogenic data agrees with that based on geomorphic parameter.
Subjects
八卦臺地
化育層指數
加權土壤剖面化育指數
土壤形態
階地對比
Pakua Tableland
Horizon index
weighted profile development index
soil morphologies
terrace correlation
Type
journal article