台灣中部晚更新世階地紅土之深層土壤碳儲量時間序列及其在地形上之意義

土壤有機碳在不同化育時間長度下顯示出儲存量與速率均有差異。台灣中部的八卦台地有多層次的河階發育，表面為紅壤或紅化之礫石層所覆蓋。在八卦台地南段有完整的土壤時間序列，其土壤年代介於19-400 ka。以此為基礎推估同一區域缺乏土壤年代資料的八卦台地中、北段河階地的深層土壤碳封存值與土壤化育程度之關係，結果支持著土壤碳封存的時間序列。在本研究中，比較以全剖面深度計算的總碳儲量（TCS）及去除人工採樣在每個樣點土壤剖面深度的不一致，以平均加權碳儲量（WCS）方式計算，其八卦台地1公尺土壤深度之平均碳儲量為2.8～3.2×10^9 kg。與現有土壤年齡資料，擬合出八卦台地土壤有機碳的累積速率方程式為CAR=0.7368e^(-0.009(Age))，推估出八卦台地中、北段階地之碳儲量之預測值，對比預測值與實測平均值平均相對誤差小於4.7％。透過Pearson相關性分析，深層土壤有機碳封存值（CSV）與加權土壤剖面化育指數（WPDI）及土壤年齡均呈現很高的相關性。說明了在台灣地形階地對比的應用上，計算深層土壤碳封存值有其方便性與可靠性，可提供河階地形演育對比研究參考。

關鍵字

土壤有機碳；碳儲量；土壤時間序列；河階地形

並列摘要

There are multiple levels of river terraces developed on the the Pakua tableland in central Taiwan, which have been well constrained with absolute ages ranged at 19-400 ka. The surfaces of these terraces are covered by reddish or lateritic soils in Taiwan. They form an ideal soil chronosequence to explore the soil organic carbon (SOC) stocks and its change through time. In this study, five soil pedons were analyzed. The total carbon stocks (TCS) justified by the total thickness of the soil profile, giving the weighted carbon stocks (WCS), is presented for comparison. The result shows the overall carbon stocks are estimated at 2.8-3.2 ×10^9 kg, in terms of TCS and WCS, for the soils of the Pakua tableland. The data of WCS and the available soil ages give a soil organic carbon accumulation rate of CAR=0.7368e^(-0.009(Age)), allowing further estimation of carbon storage in the middle and northern terraces of the Pakua tableland. The discrepancy between the predicted and the measured average value is less than 4.7 %. The exponential function carbon sequestration value (CSV) from the exponential fitting curve of the soils are closely related to soil ages. The value of CSV linearly decreases through time. The examples in this study demonstrate the correlation for the soils without age that can be achieved by the degree in pedogenesis in an agreement with those determined by CSV in this study. It reveals the potential of using carbon storage for a chronometric application.