水稻冠层光谱反射特征及其与叶面积指数关系研究

在水稻试验小区,通过人为控制的方法造成施N水平的差异,对水稻整个生长期内冠层光谱进行了比较系统、密集的测定,并测定了水稻几个重要生育期的叶面积指数。结果表明:随着施N水平的提高,水稻冠层光谱在各生育期呈现出一定的规律性,在近红外部分(760 ~ 1220 nm),冠层光谱反射率随着施N水平的提高而升高,而在可见光部分(460 ~ 710 nm),水稻冠层的光谱反射率反而逐渐降低。冠层光谱经差异显著性检验发现:水稻灌浆期以前,对施N水平最为敏感的波段是绿光(560 ~ 610 nm)和近红外(710 ~ 760 nm)部分;转换为归一化植被指数(NDVI)以后,差异最显著的是 (R760 - R560) / (R760 R560)。对叶面积指数与冠层光谱反射率的相关分析结果表明:在水稻抽穗期以前,叶面积与冠层光谱反射率相关性较差;而抽穗期以后,二者有较好的相关性。

RICE CANOPY SPECTRAL REFLECTANCE AND LEAF AREA INDEX

Canopy spectra of plots of rice field treated with different nitrogen levels were periodically and continually measured during the whole growing period and LAI of the crop at several important growing stages was also determined. The results showed that despite different growing stages, rice canopy spectral reflectance changed regularly when the nitrogen fertilizer application rate increased. With the application rate of nitrogen fertilizer increasing, the canopy spectral reflectance increased at 710~1220nm , but decreased at 460~680nm. The variation of the canopy spectral reflectance at different nitrogen levels were analyzed and compared. The results showed that the canopy spectral reflectance was sensitive to nitrogen levels in 560~610nm and 710~760nm before milking. After transforming canopy spectral reflectance into normalized difference vegetation index (NDVI), (R760-R560)/(R760 R560) was significantly different at different nitrogen levels. In addition, the correlation coefficient between LAI and canopy spectral reflectance was low before the heading period, however, was high after the heading period.