Study On Estimation Of Chlorophyll Content Based On Model Simulation And OLI Remote Sensing Image

About70%of land surface of the earth is covered by vegetation, so green vegetation is afundamental component of terrestrial ecosystem. Vegetation plays an important role in soilformation, manufacture of oxygen, water and soil conservation, air purification, eliminationof noise, climate regulation, wind prevention and sand fixation, animal habits and sterilization.Vegetation contains substances and trace elements, such as chlorophyll, water, dry matter,nitrogen and carbon, which are known as biochemical components of vegetation. Chlorophyllcontent can reflect nutrient stress, photosynthetic capacity and growth stage of vegetationand environment influence.In May,2013, we made field measurements in Luancheng county of Shijiazhuang city,the latitude, longitude and altitude, LAI, height, mean leaf angles (MTA) and photosyntheticactive radiation (PAR) of winter wheat were obtained. By setting certain parameters ofPROSPECT+SAIL model, vegetation canopy spectra are simulated. The relationship betweenchlorophyll content and vegetation indices, view zenith angle and LAI are analyzed. Theestimation model of chlorophyll content of vegetation is constructed. Chlorophyll content ofwinter wheat was estimated using Landsat-8OLI image on May19th,2013. The mainconclusions are as follows:(1) The spectra, physiological and biochemical parameters of winter wheat are obtainedby field measurements. The measured LAI range of wheat in the study area is2.135-6.445,the mean is4.161.The mean leaf angle range of wheat is28°-63.5°, the mean is56.16°. Theheight range is64-83cm, the mean is76.373cm.(2) PROSPECT+SAIL model is used to simulate canopy reflectance of vegetation. Inmodel simulation, the typical LAI values (4and6) of winter wheat are selected. As for viewzenith angles,0°,36°and55°are selected according to imaging angles of CHRIS sensor.Other angles include40°,60°and90°. This study can provide the theoretical basis forestimating chlorophyll contents using multiple angles.(3) The relationship between canopy reflectance of vegetation, chlorophyll content andview zenith angles are analyzed. At the same waveband, canopy reflectance increases with theincrease of view zenith angles. Under different view zenith angles, the difference of canopy reflectance at680-2400nm is not great when chlorophyll content are40μg/cm2and65μg/cm2.At visible band, chlorophyll is the main factor to influence canopy reflectance, and canopyreflectance decreases with the increase of chlorophyll content. With the increase of LAI, theinfluence of view zenith angle on canopy reflectance decreases, that is to say, when vegetationis sparse, the sensitivity of canopy reflectance to view zenith angle is high. Under the sameview zenith angle, the higher LAI is, the higher the canopy reflectance is.(4) The relationship between NDVI and LAI under different chlorophyll contents andview zenith angles are analyzed. Under certain chlorophyll content, NDVI increases with theincrease of LAI. Under certain LAI, NDVI decreases with the increase of view zenith angle.When chlorophyll content is greater than or equal to35μg/cm2, and LAI is greater than1.5,the smaller the view zenith angle is, the greater the corresponding NDVI is. But when LAI isnot greater than1.5, the smaller the view zenith angle is, the smaller the corresponding NDVIis. Under certain chlorophyll content, with the increase of LAI from1to7, the changeamplitude of NDVI between0°and90°view zenith angle increases. With the increase of LAI,when chlorophyll content is high, the change amplitude of NDVI under different view zenithangles is small.(5) The relationships between chlorophyll content and many vegetation indices areanalyzed. When LAI are4or6, the best indices to estimate chlorophyll content are MCARI705and CIred edge, their correlation are close to1under different view zenith angles. The nextindices are GRVI and MCARI670, the worst is DVI.(6) Landsat-8OLI image is used to establish estimation model of chlorophyll content.The distribution map of chlorophyll content in the study area is obtained using the estimationmodels of chlorophyll content which are established by RVI, GRVI and NDVI.