生长期冬小麦冠层光谱特征分析

Characteristics of Canopy Reflection Spectrum of Winter Wheat in Growth Period

采用野外地物光谱仪对样地冬小麦进行实地测量,对实测冬小麦光谱数据进行了分析。结果表明,①冬小麦冠层光谱反射曲线走势大致与绿色健康植物的一般光谱特征一致,冬小麦的生长状况都比较良好,在7个生长阶段中,变化主要发生在开花期、灌浆期;②比较整个生长期内各个波段的反射率,变化最大的为黄光波段和绿光波段,其次是红光波段和橙光波段,红外波段与蓝光波段较小,紫外波段的反射率在各个阶段的变化均远小于其他波段。在可见光波段,冬小麦冠层光谱的反射率是比较稳定的,变化集中表现在红光及近红外波段;③随着太阳高度角的增大,其各个波段的反射率均呈上升趋势,在11∶20太阳高度角接近最大时反射率达到最大,接着随太阳高度角的减小,冬小麦各个波段的反射率呈下降趋势;④叶面滞尘量和种植密度对于冬小麦光谱曲线均有影响,但由于条件限制和外界因素影响,未能精确地分析这两种因素对于冬小麦光谱曲线的影响特征。

The canopy spectral reflectance of winter wheat observed by mobile spectral radiometer in field survey was ana- lyzed. The research result showed that, ①the curve of wheat canopy spectral reflectance was similar with the normal spectral reflectance of healthy green plants. The growth conditions of wheat were all well. During 7 growth periods, the variation mainly occurred at flowering period and filling stage. ②Comparing the reflectivity of different wave bands during the whole growing period, it was found out that the biggest change was in the yellow light wave band and green light wave band, fol- lowed by red light wave band and orange wave band, the variation in infrared band and blue wave band was little; the vari- ation in ultraviolet wave band among different period was much less than that of other wave bands. The canopy spectral re- flectivity was stable in visible light bands; the change mainly occurred in the red and near infrared bands. ③The canopy spectral reflectivity of winter wheat increased with the increase of solar altitude angle, reached the highest reflectivity at 11：20 am local time, and then decreased with the decrease of solar altitude angle. ④The absorbing dust on leaf and plant density affected the canopy spectral reflectance of winter wheat, however, due to the research conditions and environment, the effective characteristic of the two factor was not clear.