Guangyin Hu

Change of lake area in the southeastern part of China’s Badain Jaran Sand Sea and its implications for recharge sources

Understanding the relationship between the changes in lake water volume and climate change can provide valuable information to the recharge sources of lake water. This is particularly true in arid areas such as the Badain Jaran Sand Sea, an ecologically sensitive area, where the recharge sources of lakes are heatedly debated. In this study, we determined the areas of 50 lakes (representing 70% of the total permanent lakes in this sand sea) in 1967, 1975, 1990, 2000 and 2010 by analyzing remote-sensing images using image processing and ArGIS software. In general, the total lake area decreased from 1967 to 1990, remained almost unchanged from 1990 to 2000, and increased from 2000 to 2010. Analysis of the relationship between these changes and the contemporaneous changes in annual mean temperature and annual precipitation in the surrounding areas suggests that temperature has significantly affected the lake area, but that the influence of precipitation was minor. These results tend to support the palaeo-water recharge hypothesis for lakes of the Badain Jaran Sand Sea, considering the fact that the distribution and area of lakes are closely related to precipitation and the size of mega-dunes, but the contemporaneous precipitation can hardly balance the lake water.

High-altitude aeolian research on the Tibetan Plateau

Aeolian processes and their role in desertification have been studied extensively at low elevations, but have been rarely studied at high elevations in areas such as the Tibetan Plateau, where aeolian processes were active in the geologic past and remain active today. In this review, we summarize research that improves our understanding of aeolian processes on the Tibetan Plateau, including the distribution, characteristics, and provenance of aeolian sediments; the history of aeolian activity; aeolian geomorphology; and wind-driven land degradation. Contemporary aeolian processes primarily occur in dry basins, in wide river valleys, on lakeshores, on mountain slopes, and on gravel pavements. Sediment characteristics suggest a local origin, and provide interesting contrasts with those of Chinas Loess Plateau. The history of aeolian activity and its paleoclimatic implications, reconstructed based on aeolian archives, is short (mostly since the Late Glacial) and shows wide regional differences. Aeolian geomorphology is simple and suggests short formation time. Wind-driven land degradation is less severe than previously thought, driven by different factors in different areas, and exhibited complex interactions with freeze–thaw processes. Aeolian research has been conducted within the general framework of aeolian science, but addresses issues specific to the Tibetan Plateau that arise due to the low air temperature, low air density, and the presence of a cryosphere. We propose six priorities for future research: aeolian physics, the effect of freeze-thaw cycles, comparisons with other areas, regional differences, effects of wind-driven land degradation, and integrated observation and monitoring.

Aeolian desertification monitoring in the Source Region of Yellow River by remote sensing technology

The Source Region of Yellow River locates in the hinterland of Qinghai-Tibet Plateau, which is especially sensitive to global environment change because of its high elevation and cold environment. Under the influence of global warming, aeolian desertified land expanded rapidly in this area during the last decades. To assess the trends of aeolian desertification from 1975 to 2005, we employed remote sensing and GIS technology to monitor the extent of aeolian desertification at four times (1975, 1990, 2000, and 2005). The data sources included Landsat multi-spectral scanner (MSS) images acquired in 1975 with an 80-m spatial resolution, Enhanced Thematic Mapper (ETM+) images acquired in 2000 with a 30-m resolution, and Thematic Mapper (TM) images acquired in 1990 and 2005 with a 30-m spatial resolution. The remote sensing monitoring result shows that the area of aeolian desertification land increased rapidly between 1975 and 1990, kept stable between 1990 and 2000, and turned to decrease slightly between 2000 and 2005.

Land use and land cover change monitoring in the Source Region of Yellow River by remote sensing technology

The Source Region of Yellow River locates in the northeast of Qinghai-Tibet Plateau with an area of 131419 km2, which is especially sensitive to global warming because of its high elevation and cold environment. To assess the land use and land cover changes from 1975 to 2005, we employed remote sensing and GIS technology to monitor the area of land use and land cover at four times (1975, 1990, 2000, and 2005). The data sources included Landsat multi-spectral scanner (MSS) images acquired in 1975 with an 80-m spatial resolution, Enhanced Thematic Mapper (ETM+) images acquired in 2000 with a 30-m resolution, and Thematic Mapper (TM) images acquired in 1990 and 2005 with a 30-m spatial resolution. The monitoring result shows that, under the influence of global warming and human activities, the Source Region of Yellow River experienced an overall environmental degradation between 1975 and 2005. The environmental degradation includes deforestation, grassland degradation, cultivated land increasing, sandy land expansion and wetland shrinking.

Monitoring land use and land cover change in the source region of the Yangtze River using multi-temporal Landsat data

The Source Region of the Yangtze River locates in the Qinghai-Tibet Plateau with an area of 142299 km2, which is especially sensitive to global warming because of its high elevation and cold environment. To assess the land use and land cover changes from 1975 to 2005, we employed remote sensing and GIS technology to monitor the area of land use and land cover at four times (1975, 1990, 2000, and 2005). The data sources included Landsat multi-spectral scanner (MSS) images acquired in 1975 with an 80-m spatial resolution, Enhanced Thematic Mapper (ETM+) images acquired in 2000 with a 30-m resolution, and Thematic Mapper (TM) images acquired in 1990 and 2005 with a 30-m spatial resolution. The monitoring result shows that, the study area experienced an overall environmental degradation between 1975 and 2005. The environmental degradation includes deforestation, grassland degradation and sandy land expansion.

Land use and land cover change monitoring in the Zoige Wetland by remote sensing

The Zoige Wetland lies in the northeastern Qinghai-Tibet plateau, a region that is highly sensitive to global environment change because of its high elevation and cold environment; thus, its a hotspot for land use and cover change (LUCC) research. In this study, we used Landsat images to monitor LUCC in this region using GIS techniques, as well as topographic, vegetation, and soil maps combined with field investigations. LUCC processes from 1975 to 2005 in the Zoige Wetland were gained through visual interpretation of multi-temporal remote-sensing images at a scale of 1:100,000. The monitoring result shows that the regions eco-environment degraded steadily in the 30 years.