基于高光谱的苹果果期冠层光谱特征及其果量估测

苹果冠层光谱特征是苹果树遥感生理监测和生产管理的重要依据。对栖霞市苹果果期的冠层反射光谱进行实测,结合数码照相技术探明了苹果果期的反射光谱特性和敏感波段,并通过敏感波段与果树比指标建立回归模型,实现了对苹果冠层果量(果树比)的无损估测。结果表明:苹果树果期冠层光谱曲线总体表现为对蓝光和红光的吸收及对绿光的反射,在近红外750—1300nm之间表现为强烈的反射,且在1650nm和2200nm附近呈现两个反射峰。选择435、670、730、940、1140nm和1480nm等6个波段为苹果果期的敏感波段。利用这些波段分别构建了差值、比值及归一化植被指数,筛选了最佳光谱参数,进而构建了果量(果树比)估测模型,经筛选验证确定苹果果量的最佳估测模型为:y=0.0086NDVI(940,730)]2-1.0934NDVI(940,730)+0.3209。模型为苹果果期果量的精确估测提供了比较快捷的方法途径。

Canopy spectral features and fruit amount estimation of apple tree at fruit stage based on hyperspectral data

Canopy spectral characteristics of apple tree are the basis for apple physiological monitoring with remote sensing and production management. This study carried out the measurement of apple tree canopy spectral reflectance at apple fruit stage in Qixia City. The reflective spectral features and sensitive wavebands of apple tree canopy at fruit stage were initially explored and regression models between sensitive bands and the ratio of fruit/tree were established with digital photography techniques. The non-destructive estimation of fruit amount (fruit/tree ratio) was realized. The results showed that the spectral features of apple tree canopy at fruit stage mainly presented as absorption of blue light and red light, reflection of green light, and the strong reflection of near-infrared between 750nm to 1300nm, with two reflection peaks near 1650nm and 2200nm. The sensitive bands to fruit amount were 435nm, 670nm, 730nm, 940nm, 1140nm and 1480nm. Vegetation indices of difference, ratio and normalized difference were built respectively with the sensitive bands, and the best spectral parameters were selected. Estimation models of fruit amount (fruit/tree ratio) were established accordingly and the best model was evaluated and validated as y = 0.0086\NDVI (940,730)\]2-1.0934NDVI (940,730) + 0.3209. This model is expected to provide a relatively fast and accurate estimation method for canopy fruit amount at apple tree fruit stage.