不同氮素水平下油菜高光谱特征分析

利用小区试验获得的油菜主要生育期的冠层反射光谱,对不同品种、不同生育期和不同供氮水平下油菜冠层光谱进行了特征分析.结果表明:对于不同品种和不同生育期,冠层光谱分别在近红外和可见光区域存在一定的差异;对于不同的施氮水平,随着施氮水平的提高,在可见光区域反射率值减小,而在近红外区域则呈相反的变化趋势;一阶导数光谱随着施氮水平的增加,具有向长波方向移动的趋势,同时随施氮水平的增加,"双峰"现象则愈显著.红边位置随生育期和氮素水平的变化不明显,红边面积与红边幅值几乎在所有的生育期中呈现出随着供氮水平的提高而表现为增大的趋势.对于同一供氮水平下不同生育期,冠层红边面积与红边幅值随着生育期的推移呈"波浪"形状变化趋势.

ANALYSIS ON HYPERSPECTRAL CHARACTERISTICS OF RAPE AT DIFFERENT NITROGEN LEVELS

The hyperspectral reflectance for rape canopies is acquired in primary growth stages in order to monitor rape status and diagnose nitrogen.The corresponding first derivate spectra are obtained.The analysis on canopy spectral reflectance and derivate spectra under different cultivars and different growth stages shows that the canopy reflectance for different cultivars has significant change at near infrared band and visible band respectively.Reflectance at visible region decreases with the increasing nitrogen and conversely at near infrared region.Derivate spectra have the trend of shift to long wavelength direction and exist "two peak" phenomena at more significant increase of the nitrogen level.Red edge position of canopy reflectance spectra does not change remarkably with growth stages and nitrogen levels.The area of red edge and red edge amplitude increase with the augment of the nitrogen supply almost at all growth stages and show a wave shape with growth progress under the same nitrogen level