Study On Vegetation Coverage And Its Dynamic Change By Remote Sensing

Vegetation coverage,the ratio of vegetation occupying a unit area is a very important parameter in the study of climate and ecological models , and a comprehensive index of the earth's surface situation covered by vegetation community. The change and the estimation of vegetation coverage is important in the study the change of ecology-environment syetem, hydrology, ecology and world environment change.This paper introduces the basic theories, the study status and the developing direction of the methods of measuring vegetation coverage. Estimation of vegetation coverage from remote sensing data may be a more efficient approach. Based on the method of dimidiate pixel model and sub-pixel models for vegetation coverage estimation. The current model is improved. the model of deriving vegetation fraction from normalized difference vegetation index (NDVI) is established, The improved model is estimating two important parameters of the old model, and the deducing process of the two parameters. The model can be used to all kinds of vegetation types and different scales remote sensing dataOn the base of the improved model ,a example of the POYANG LAKE , a technical program to achieve the model is designed.Following this program estimationin vegetation coverage of the POYANG LAKE district in 1989 and 2003 ,drawed the image of vegetation coverage of the POYANG LAKE district .On the spot review some area of the POYANG LAKE, testing and verifying the result of estimation of vegetation coverage of the POYANG LAKE district in 2003,the result shows that it is feasible to use this improved model in estimation of vegetation coverage from remote sensing data.In this paper on the base of estimation of vegetation coverage in two years, counted and ananlysed the average vegetation coverage of the POYANG LAKEdistrict in 1989 and 2003, drawed the grade of vegetation coverage of the POYANG LAKE district in recent 14 years changing in space process and tendency of this change.In the total ,the change of vegetation coverage is not obvious,but to the different district this change is obvious.This shows the fact that there exist unbalance vegetation coverage of developed and undeveloped distracts in the POYANG LAKE. And this unbalance to show that human action can influence natural ecology greatlyjt is vital for us to harmonize humanity and nature.According to the analysis of the estimation of vegetation coverage on the POYANG LAKE, the model can be considered as a useful method to large areas estimation of vegetation coverage. It can supply the requires of the change of ecology-environment syetem and climate. Because the model needn't the complex parameters as the LAI index. The principle is easy to be understood and grasped. It can reach the process extent. The model is a efficient way which observes the change of vegetation coverage.