玉米冠层叶片光谱反射率与玉米长势空间变异的关系

为了寻找一种快捷获取玉米叶绿素空间分布信息的方法,研究了玉米苗期冠层叶片光谱反射率的变化特征,分析了不同生长阶段冠层叶片光谱反射率的空间分布和叶绿素质量浓度的空间分布.研究结果表明:玉米苗期冠层叶片叶绿素的质量浓度空间分布不均匀.冠层叶片的叶绿素质量浓度与光谱指数RVI的相关性较低,与归一化差异植被指数NDV1值和550 nm波段的反射率均有较高的相关性.分析550nm波段的反射率值与冠层叶片叶绿素质量浓度值的相关关系,显示二者成负相关变化趋势,相关系数绝对值在0.69～0.88范围随着生长期的变化而逐渐增大,五叶期前期的相关性系数绝对值达到苗期最大值,表明550 nm波段反射率值能够较好的反映玉米苗期叶绿素质量浓度的水平,分析和掌握550 nm波段反射率值的变化及其空间分布特性对快速监测玉米苗期生长状况,对指导田间施肥具有重要意义.

Spatial variability and relationship of spectral reflectance and growth status to corn canopy

In order to find out a convenient way of acquiring chlorophyll spatial distribution, the canopy spectral reflectance of corn seedlings was measured. The spatial distribution of canopy spectral reflectance and the chlorophyll content were analyzed on different growth stages. The results indicated that the spatial variability of the canopy chlorophyll content of corn was unstable at different growth stages. The variance was kept in a higher level over the growth stages. The correlation coefficients between chlorophyll content of corn canopy leaf and each vegetation index, NDVI, RVI, and spectral reflectance of 550 nm, were calculated. The chlorophyll content showed better correlation with NDVI and reflectance of 550 nm, while there was no high correlation between chlorophyll content and RVI. Focus on the relationship between reflectance of 550 nm and chlorophyll content, it was found that the correlation coefficient varied among -0.88~-0.69, and the highest value was observed at the early period of the five-leaf stage. It showed that the reflectance at 550 nm might characterize the chlorophyll content of corn canopy leaves. The method can be used to support the precision fertilization during the growth stages of corn.