Remotely Sensed Analysis Of Cadium Stress Based On The Changes In Physiological Function Of Rice

Heavy metal stress influences the physiological and biochemical parameters of crops,and lead s to changes in energy absorption,release and radiation.In view of the concealment and stability of heavy metal stress,the main methods generally extracted the characteristics of crop appearance and leaf structure change from the perspective of spectral information enhancement,or analyzed the change of biomass from the perspective of time series analysis,but rarely analyze heavy metal stress on the physiological function of rice in the view of energy balance.In this paper,considering the accumulation of cadmium stresses,concealment and stability,physiological parameters of physiological function and interaction between physical elements during the rice mature period were used to identify different stress levels.In this study,the effects of cadmium stress on the physiological functions of rice were studied using the mechanism of heavy metal stress.The effects of cadmium stress on the photosynthesis of rice were studied from the point of view of energy absorption by using hyperspectral bands reflectance of visible light and Fraction of Absorbed Photosynthetically Active Radiation(FAPAR)and Hyperspectral reflectance as sensitive parameter s.The results showed that cadmium stress could inhibit rice light absorb tion,resulting in the increase in reflectance and the decrease in FAPAR.The effects of cadmium stress on the transpiration of rice were analyzed from the perspective of energy radiation using Tca as sensitive parameter.The results showed that cadmium stress could affect the release of canopy energy,which led to the enhancement of canopy radiation energy.In order to realize large-scale monitoring of cadmium stress in rice,Landsat-8 remote sensing image,measured data and environmental data are used to invert sensitive parameters of rice physiological function.The effects of cadmium stress on the light absorption of rice were explored and analyzed using visible light albedo ?rb and FAPAR.The results showed that cadmium stress could affect the light absorption of rice,and ?rb and FAPAR could well recognize mild cadmium stress.Based on the energy balance model,the transpiration parameters Tca and latent heat flux(LE)of rice were inversed.The results showed that cadmium stress could inhibit the transpiration rate of rice,and Tca and LE could well recognize severe cadmium stress.However,the energy absorptionrelease and radiation sensitive parameters can distinguish between only two different stress level.In order to improve the recognition accuracy,this paper introduces the method of feature integration,the ?rb-LE feature space and the physiological function sensitivity index Pf were constructed by combining the visible light albedo ?rb,FAPAR,and LE parameters.The results show that the accuracy of ?rb-LE feature space was 99%,88% and 85%,respectively,and the accuracy of Pf was 72.84%,78.95% and 90.42%,respectively,for different stress(low / medium / high stress)of rice.According to the large area inversion results,we found that the area of heavy cadmium pollution is mainly distributed near the Xiangjiang River.The rice is gradually changed from heavy cadmium to mild cadmium pollution with decreasing distance from the Xiangjiang river.