Remote Sensing Based Vegetation Change And Biophysical Effects On The Loess Plateau

Vegetation cover change is one of the important way of human activities on the climate. The interaction between vegetation cover change and climate change would have an important effect on the global scales ecosystem and global environment in the local, region and global scale. Thus it would have important influence on the global climate directly or indirectly. It not only can affect the climate system through the adjustment function of Carbon, but also can play an important role on the climate through the land surface property, including albedo, roughness, and surface soil moisture and so on. Therefore, take the different ways which vegetation cover change have on the climate change into account is an urgent need for a scientific understanding of the impact of land cover change on climate system.The Loess Plateau is one of the fragile environmental area in China, which has attracted wide attention and has become one of the first batch of "returning farmland to forest and Grassland" project. This paper took the Loess Plateau as the study area. Combined the surface vegetation cover types, DEM, climate, survey data and multiple MODIS remote sensing data products, the Loess Plateau vegetation cover change and role of physical biological were analyzed. And this study can provides an important scientific basis for grasping the regional terrestrial ecosystem change and its effect on Regional climate change. The main results as follows:(1) Through the analysis of vegetation changes in 2000-2010, the vegetation coverage on the whole of the Loess Plateau was increased in both time and space. The vegetation restoration in different grades of slope had a significant improvement trend in 2000-2014, and this phenomenon indicated that many years of ecological construction activities have remarkable results.(2) From the aspects of biological indicators, the EVI, LAI and fPAR all showed a consistent upward trend in space and time respectively. EVI had a significant positive correlation with the vegetation coverage, while the correlation with the annual average temperature and annual precipitation was not significant. And this results showed that the project of returning farmland to forest and grassland had great contribution to the increase of surface vegetation cover and the increase of the productivity of vegetation.(3) From the aspects of physical indicators, the Albedo and LSTday had a downward trend in the time and space nearly 15 years. The temporal and spatial variation characteristics of LSTnight was stable. Through the analysis of Albedo, LSTday, LSTnight and ET and so on in the different surface cover types, we can found that in the process of returning farmland to forest (grass), the changing of cultivated land to forest would lead to the Albedo decreased and ET increased. And the increased ET would lead to the Albedo decreased.(4) VCF was parameters which reflect the land surface vegetation cover condition. The relevance of physical parameters Albedo, daytime surface temperature, and surface temperature at night with VCF were analyzed. The results showed that there was a significant negative correlation between vegetation coverage and Albedo in the Loess Plateau region, which indicated that afforestation could lead to the decrease of Albedo and the increase of ET in the Loess Plateau. The decrease of Albedo can lead to the increase of surface temperature. The increase of ET in the surface temperature had the effect of cooling, and the effect of the temperature synthesis on the surface of the earth may mutually offset.In a word, the Loess Plateau as a pilot area of farmland to forest, its vegetation cover condition had a significant improvement nearly 10 years, and this can be reflected by the biological indicators. Duo to the vegetation cover change have different effects on the different biological and physical characteristics, different these effects may offset each other, and so the vegetation cover change may had no significant effect on the temperature. But vegetation coverage increase in the area of ecological restoration very positive effect.The main innovation of this paper as follows:Based on the MODIS remote sensing data, the changes of surface vegetation cover and the temporal and spatial characteristics of the Loess Plateau were studied. Recently, the research on the physical parameters of the MODIS single surface is more common. But the comprehensive research on the physical characteristics of the surface still lack and need study further. This paper took the Loess Plateau region as the study area, compared with different types of land cover parameters, and took the relationship between the parameters into account. In the study of the Loess Plateau, there were not many related researches on the characterization of vegetation changes in a comprehensive and comprehensive consideration.