水稻微分光谱和植被指数的作用探讨

通过两年两个不同品种水稻在不同供氮水平下的田间试验，测定了水稻冠层在生长过程中不同时期的高光谱反射率及对应的叶绿素、类胡萝卜素含量，分析了微分光谱对消除水稻冠层光谱的背景影响和植被指数在农学参数测定中的作用。结果表明：由微分光谱所得的红边位置、红边斜率与盖度和供氮水平之间有一定的相关性，与叶面积指数、地上生物量及冠层叶绿素、类胡萝卜素含量有显著相关；水稻多光谱植被指数RVI、NDVI与叶面积指数LAI及其地上部生物量之间有极显著相关性；高光谱植被指数及其变量与植被盖度、供氮水平、叶面积指数、地上生物量及叶绿素、类胡萝卜素含量之间存在相关性。这表明，用微分光谱技术与植被指数方法来监测水稻的色素含量和长势应该是可行的。

Action of derivative spectra and vegetation indices for rice

The hyperspectral reflectances of the canopy of two varieties of rice were measured by an ASD FieldSpec Pro VNIR^TM and an ASD FieldSpec Pro FR^TM in field under different nitrogen levels at different stages in two years. The concentrations of chlorophyll and carotenoid of canopies corresponding to the spectra were determined by biochemical method. The action of derivative spectra on eliminating background influence on rice canopy spectra and that of vegetation indices on determining agricultural parameters were analyzed. The result shows that the position and slope of red edge of canopy spectral reflectance of rice are certainly correlative to fractional vegetation cover and nitrogen supply level. The leaf area indices, above ground fresh biomass, above ground dry biomass, the concentrations of chlorophyll-a, chlorophyll-b, total chlorophyll and carotenoid of canopies are significantly correlative to the position of red edge and slope of red edge of the canopy spectra. The multiple spectral vegetation indices RVI and NDVI of rice canopy are very significantly correlative to LAI and above ground matter, but the hyperspectral vegetation index and its variable are certainly correlative to rice fractional cover, nitrogen supply level, leaf area indices, above ground fresh biomass, above ground dry biomass, the concentrations of chlorophyll and carotenoid of canopies. This proves that it is feasible to use the technology of derivative spectrum and the method of vegetation index to monitor the pigment concentration and growth of rice.