利用植被光譜特徵估測莧菜植株生長及氮素狀態

Estimating Growth and Nitrogen Status in Plants of Amaranthus mangostanus with Canopy Spectral Characteristics

楊純明(Chwen-Ming Yang) ； 吳正宗(Jeng-Tzung Wu) ； 沈百奎(Bor-Kwei Shen) ； 余志儒(Jih-Zu Yu) ； 羅朝村(Chaur-Tsuen Lo) ； 申雍(Yuan Shen)

《中華農業研究》 52卷4期 (2003/12) Pp. 268-290

https://doi.org/10.29951/JARC.200312.0003

摘要

本研究量測2001-2002年三不同作季採收時莧菜(Amaranthus mangostanus)植被反射光譜及植株性狀，以探討利用植被光譜特徵估測莧菜植株生長及氮素狀態之可行性。由量測光譜範圍(350-2400nm)各窄波段反射比與調查性狀之簡單直線相關強度分析，可知各窄波段反射比與各調查性狀之相關程度不一，地上部鮮產量、葉片葉綠素總量、乾物質百分比、葉面積、地上部植體硝酸鹽含量及全氮含量等性狀之相關係數絕對值最大之窄波段位置分別座落於767、574、779、574、1975及577nm。將另一作季田間試驗之各光譜特徵反射比輸入直線迴歸模式，僅葉片葉綠素總量及地上部植體全氮含量之估測值與實測值相關顯著。續分析八種植被光譜指數與六種調查性狀之關係，顯示地上部鮮產量、地上部植體全氮含量、葉片葉綠素總量分別與不同光譜指數呈現曲線或直線關係。經將另次試驗光譜資料輸入相關模式求出估測值與實測值比較後，此三性狀之估測值與實測值相關均達顯著。由多元直線複迴歸分析，地上部鮮產量及全氮含量可以二元直線迴歸模式表示，葉面積可以三元直線迴歸模式表示，葉片葉綠素總量、地上部植體乾物質百分比及地上部植體硝酸鹽含量則可以四元直線迴歸模式表示。經另次試驗光譜特徵輸入各模式求出估測值與實測值比較後，除了葉面積之外，其餘五項性狀之估測值與實測值相關均達顯著。

關鍵字

植被光譜特徵 ； 莧菜 ； 植株生長 ； 氮素狀態 ； 多元線性複迴歸分析

並列摘要

Field experiments were conducted at the experimental farm of Taiwan Agricultural Research Institute (Wufeng, Taiwan) to measure canopy reflectance spectra and plant characters of Amaranthus mangostanus L. (cultivar TNG 1) grown in the growing seasons of 2001-2002. From the simple linear correlation analysis between plant characters and canopy spectral reflectances in the range of 350-2400nm, it showed that various correlation coefficients existed along the measured spectral wavebands. The narrow wavebands with the maximum absolute value of coefficients were located at 767nm (r=0.741(superscript **)), 574nm (r=0.492(superscript *)), 779nm (r=0.645(superscript **)), 574nm (r=0.628(superscript **)), 1975nm (r=0.697(superscript **)) and 577nm (r=-0.506(superscript *)) for aboveground fresh yield, leaf total chlorophyll, percent dry matter, leaf area, nitrate content and nitrogen content, respectively. Regression models validation by using data from another experiment showed a significant correlation between the estimated and the measured values in leaf total chlorophyll and aboveground nitrogen. By analyzing of the relationships between plant characters and canopy spectral indices, it indicated that aboveground fresh yield was linearly correlated with GREEN/NIR ratio, RED/NIR ratio and NDVI, aboveground nitrogen was curvilinearly correlated with GREEN, RED/NIR ratio, GREEN/RED ratio and NDVI, and leaf total chlorophyll was also curvilinearly correlated with GREEN and GREEN/RED ratio. These regression models were validated effective with another set of experimental data. By the multiple linear regression analyses, fresh yield and aboveground nitrogen were fitted to 2-variable regression models with the determining factors of 0.852 and 0.761, respectively. Leaf area can be estimated with a best 3-variable regression model (R^2=0.545), while leaf total chlorophyll, percent dry matter and nitrogen content can be assessed with the best 4-variable regression models, with R^2 of 0.697, 0.693 and 0.822, respectively. However, regression model for leaf area was found not feasible to the data from another experiment. Results suggest that plant growth and nitrogen status of vegetable amaranth may be estimated reasonably by the regression models from canopy spectral characteristics.

並列關鍵字

Canopy spectral characteristics ； Amaranthus mangostanus ； Plant growth ； Nitrogen status ； Mutiple linear regression analysis