Abstract: By using ASD FieldSpec 3 field spectrometer, the hyperspectral reflectance of apple flowers at full-blooming stage was measured under laboratory conditions, and the correlations of the hyperspectral reflectance with the phosphorus content of apple flowers were analyzed based on the original spectrum and the first derivative spectral characteristics of the flowers. The sensitive wavebands were determined, the characteristic spectral parameters were constructed, and the monitoring models for the phosphorus content of apple flowers were established accordingly. Correlation analysis showed that the phosphorus content of apple flowers was significantly positively correlated with the original spectral reflectance at 350-370 nm, 670-1385 nm, and 1620-1760 nm, and the first derivative reflectance at 500-520 nm, and significantly negatively correlated with the first
derivative reflectance at 670-730 nm. The spectral parameters DVI (936,676), DVI (977,676), NDVI (936,676) and NDVI (977,676) had close correlations with the phosphorus content of apple flowers, the correlation coefficients being all >0.77. By using these spectral parameters as independent variables, four monitoring models for the phosphorus content of apple flowers were established, among which, the model with NDVI (936,676) as the variable was validated as the best monitoring model, its determination coefficient was the highest (R²=0.9385), root mean square error and relative error were the smallest (RMSE=0.6883, and RE=7.6%), and prediction accuracy reached 92.4%.

Key words: apple flower, hyperspectrum, phosphorus content, monitoring model, source area of urban heat island, sink area of urban heat island, source and sink index of heat island, land surface temperature.