應用衛星影像估算水稻田之植生參數與二氧化碳通量

Abstract

本研究透過現地量測與Landsat-7ETM+衛星影像兩種尺度偵測水稻田之植生參數於水稻生長期間變化，並探討植生參數與二氧化碳通量之間的相關性。 本研究方法使用Gobron(2006)提出的大氣修正法估算植生冠層入射光合有效輻射吸收率(FAPAR)，並使用Monteith(1972)提出的光能利用率模式估算淨初級生產量(NPP)，最後探討常態化差異植生指標(NDVI)、FAPAR、NPP與渦流相關法(Eddy covariance method)估算求得二氧化碳通量之相關性。衛星影像選擇空間解析度30公尺的美國大地衛星(Landsat-7ETM+)，空間尺度較接近研究區域，將同樣的計算方式應用在衛星影像，最後將現地實驗估算結果與衛星影像估算結果相互驗證。 研究結果顯示，現地估算結果皆有落在衛星影像估算結果之範圍內，代表兩者估算結果一致，另外經由NDVI、FAPAR、NPP與二氧化碳通量變化趨勢圖中，可看出NPP相較於NDVI與FAPAR，也更能偵測出與二氧化碳通量的線性反比變化趨勢，驗證Zhao(2006b)所提出NPP與二氧化碳通量存在良好負相關之論點。

The major purpose of this study is to use field measurements and Landsat-7ETM satellite images to detect the two-scale paddy field parameters in the vegetative growth period of rice, and to investigate the relationships between the vegetation indices and the carbon dioxide fluxes. In this study, FAPAR was estimated using an algorithm developed by Gobron (2005) , and the Monteith light use efficiency model was used to estimate NPP. Empirical relationships between NDVI, FAPAR, NPP and CO2 flux were established. It was found that NPP is more sensitive than NDVI and FAPAR. Such results are consistent with Zhao (2006b) that NPP is the primary driver of the atmospheric CO2 growth rate.