Quantitative Inversion And Dynamic Monitoring Of The Vegetation Canopy Water Content In The Road Area Based On Remote Sensing

The construction of high grade highway not only promotes the development of China's transportation industry,but also promotes the economic development of the area along the highway,which is convenient for personal mobility.However,the construction and operation of the highway have inevitably caused some damage to the surrounding environment to a certain extent,such as the vegetation destruction,land resources destruction,soil erosion and so on.The vegetation environment of highway road area can reflect the influence of road ecological environment during the construction and operation of the highway directly.In order to monitor the vegetation environment in the highway area,in this paper,the vegetation water content was selected as the research target factor,which can not only characterize the vegetation growth status,physiological and biochemical processes,but also measure the vegetation physiological status,morphological structure and healthy in a certain extent.In this paper,with the Hunan Province Li-Tan highway area as the study area,the Landsat7 ETM + remote sensing images as the data source,as combined with the theory of quantitative remote sensing,the method of physical model together with statistical model factor was used to retrieve the road area vegetation leaf equivalent water thickness and the leaf area index,which were in the year of 2003,2007,2010 and 2015,before and after the highway construction and during the operation.And the conversion of vegetation water content from the leaf scale to the canopy scale was realized as well,the spatial and temporal dynamic monitoring analysis of vegetation canopy water content was completed.The main research contents and conclusions were outlined as follows:(1)Based on the spectral response function of the ETM+ sensor,through building the conversion model between the measured spectrum and the remote sensing image's pixel spectral,the conversion of the spectral reflectance from the measured endmember scale to multi spectral pixel scale was realized;(2)Through the analysis of vegetation spectrum characteristic curve,six vegetation moisture indexs have been selected to establish the statistical model with the leaf equivalent water thickness respectively,and the normalized difference infrared index which was with the highest correlation coefficient has been finally selected,it was chosen as the inversion parameter of road area vegetation equivalent water thickness to enter the physical model;(3)By constructing a look-up table to achieve the inversion of leaf equivalent water thickness,with the method of PRO4 SAIL physical model combined with statistical model factor(normalized difference infrared index),and using the physical model to invert the road vegetation leaf area index at the same time,the Li-Tan highway road area vegetation canopy water content of the four years were got after the band math;(4)From the aspects of the time and spatial pattern,the method of quantitative and qualitative analysis was chosen to evaluate the change of the vegetation canopy water content in the road area.In this study,Li-Tan freeway has been chosen as the representative research object,through the research and analysis of the vegetation water content,reflecting the impact on the road area vegetation environment during the construction and operation of the highway,and providing basic support for the evaluation on the road area vegetation environment.The study can promote the application of quantitative remote sensing inversion theory in the evaluation of ecological environment,to lay the foundation of the rapid and quantitative monitoring and evaluation for highway area vegetation water content in hilly area of south China.