應用土壤轉換方程式(PTF)評估台灣平地土壤之飽和水力傳導度

Abstract

為使過去四十年所建立之土壤基本資料能加值利用，本研究利用文獻中適當之土壤轉換方程式 (Pedotransfer function, PTF)，將台灣各縣市地區之土壤調查報告中之土壤質地資料轉換成飽和水力傳導度數據。本研究利用有限的國內文獻數據，以驗證所使用PTF之適用性，結果顯示此PTF並不適用於坡地土壤；PTF推估之飽和水力傳導度約比實測飽和水力傳導度低了約1~2個數量級。然而，對於平地土壤， PTF推估之飽和水力傳導度與實測飽和水力傳導度間則有相同數量級之結果。據此，我們利用此PTF將龐大的台灣平地土壤質地資料轉換成水力傳導度資訊。在完成1,004個土系之飽和水力傳導度估算後，本研究建立台灣地區平地土壤飽和水力傳導度分佈圖，以供各相關領域參考利用。因為本研究所利用之PTF為國外文獻之經驗式，可能無法完全反映出台灣土壤之區域性土壤構造因素；因此，發展國內之PTF是另一值得研究探討之課題。 In order to advance the values of the soil basic data of Taiwan established in past forty years, this study employs the feasible foreign pedotransfer function (PTF) transferring the soil texture records to saturated hydraulic conductivity data. For evaluating whether the PTF this study applied is suitable or not, it was first tested by the limited literature data of Taiwan with both soil texture and measured hydraulic conductivity. The results indicate that the applied PTF is unsuitable for slope land soils; the soil saturated hydraulic conductivity inferred from the PTF (Ks) is lower than the measured value (Ks’) by 1~2 orders of the magnitude. However, the Ks has the same order of magnitude with Ks’ while evaluating on the plain soil; we thus transfer the vast amount of texture data of plain soils to hydraulic conductivity information accordingly. After obtaining the saturated hydraulic conductivity of soil series of plain (arable) soils in each county, a soil saturated hydraulic conductivity map with 1,004 soil series in plain area of Taiwan is hence established. The soil saturated hydraulic conductivity map will be an important reference for related fields while evaluating the ability of infiltration in a specified region. Because the foreign PTF that this study applied is a foreign experience equation and may not appropriately reflect the unique soil structure factor of Taiwan’s soils. Therefore, to develop a local PTF instead of foreign one is an important subject for further study.