PRI-LUE Model Optimization Based On Multi-angle Remote Sensing Data And Flux Data

The utilization of light energy is an important parameter for estimating the total primary productivity,which is used to represent the efficiency of the transformation of the intercepted solar energy into organic matter through photosynthesis,and is widely used in a variety of estimation models.In recent years,with the continuous development of flux observation technology,the research on the relationship between PRI and LUE on the ecosystem scale has also emerged.It has been proved that PRI has great potential in estimating LUE directly.However,it is also found that the relationship between PRI and LUE has great temporal and spatial variations,which is easily influenced by many factors such as observation angle,sun zenith angle,leaf inclination distribution and canopy structure.In this study,a large number of data were obtained by experimental observation,and the multi angle hyperspectral reflectance data of rice canopy were automatically obtained by the remote sensing platform.Based on the vorticity correlation system,we obtained the CO2 flux and other data.And carried out the field experiment to get the data of rice biomass and leaf area,then analyzed the multi angle observation data.The effect of multi angle observation on the relationship of PRI-LUE was evaluated.Using the multi angle observation data and the least square method,we constructed the two leaf PRI algorithm to eliminate the PRI value of the influence of the Yin and Yang leaves,and combined the indication effect of PRI to LUE with improving the two leaf LUE model.The main conclusions of the study are as follows:(1)The reflectivity of the red and blue light bands was obviously reduced in the heading stage to the filling stage,while the reflectance of the green band increased gradually,and the reflectivity of red and blue light bands increased in the mature period.The reflectance of the canopy in the sunny day showed an increasing trend in the morning to noon,but there was no obvious regular change in the cloudy day.The canopy reflectance increased with the increase of the observational zenith angle.When the direction of observation was in the direction of back scattering,the greater the reflectance of the canopy spectral reflectance.The combination of crop hyperspectral remote sensing data and PROSAIL model is more convenient and convenient for monitoring rice LAI and other physiological parameters and growth status.(2)PRI and LUE showed similar changes in daily scale,showing a good correlation.With the change of the observation angle,the rice canopy PRI has a significant change in size;the multi angle PRI variation span of the sunny day is larger;the PRI value of the back scatter direction is generally less than the PRI value of the direction of the forward scattering;under the different observational zenith angle,the correlation of the multi angle PRI with the LUE is the most significant when the zenith angle is 60 degrees,and the R2 is 0.5536.(3)The two leaf light energy utilization model can distinguish the different reactions between the direct and the scattered radiation in the cloudy and sunny days to a certain extent.The estimation ability of PRI to the LUE has been improved.The PRI value simulated by the two-leaf PRI algorithm is generally smaller than the measured multi-angle PRI value,and the correlation with the LUE is significantly improved.However,due to the weak radiation from the cloudy day,the optimization effect of the two-leaf PRI algorithm on the PRI is not satisfactory.(4)The simulation results of the two leaf PRI algorithm and the two leaf LUE model are synthetically analyzed.It is found that the algorithm can improve the indicator of the photochemical reflection index to the light energy utilization rate at half hour and the diurnal scale,and the application of the two algorithms can reduce the sun target observation to a certain extent.The PRI-LUE relation model is optimized by the influence of geometric factors.The estimation model of the two leaf light energy utilization ratio,including angle factors,also has high estimation accuracy,which provides a reference for the optimization of the relationship of PRI and LUE.