| Arid ecosystems, especially at high latitude or altitudes, may be strongly influenced by climate change as biological productivity of these ecosystems is limited by temperature and/or water. The Tibetan Plateau is a high latitude, high altitude cold desert which exerts a strong influence on local and global climate. Spanning ∼2.5 million square kilometers with an average elevation >4000 m, the Plateau strongly influences circulation in the northern hemisphere. Precipitation is highly variable in space and time and snow cover, because of its high albedo, exerts strong controls on climate. Snowmelt provides the primary water source for major rivers, such as the Ganges and the Indus, which originate on the Plateau and provide water for millions of people. Vegetative cover on the Plateau influences climate through regulation of the atmospheric carbon dioxide budget via photosynthesis, autotrophic respiration and biomass burning. The Plateau supports one of the worlds largest grazing systems and an pastoral economy. Because of the strong influence of the Plateau on climate, the dependence on natural resources, and the potential impacts of climate change on productivity in this region, it is critical to quantify vegetation and snow cover for this region. The purpose of this dissertation is to develop and apply more useful remote sensing methods for quantifying the spatio-temporal trends in vegetation and snow cover. Chapter one validates a newly derived snow index, which had robust validation results, and compares performance to current products. Chapter two applies the new snow index to quantifying spatio-temporal trends in snow cover on the Plateau, where significant increasing trends from 2000-2007 were found. Chapter three applies new vegetation indices and numerical analysis to quantifying the spatial dynamics of vegetative cover. Brown vegetation, previously unexamined in this region, was found to be is surprisingly dynamic. Chapter four applies the new vegetation indices to quantifying temporal trends in vegetation cover. Significant increasing trends in grassland and forested regions of the Plateau were found. These results significantly contribute to the understanding of land surface dynamics in this region and provide new, more rich methods, which can be applied to arid regions globally. |
