Author(s): Xu Mengzhen; Li Yanfu; Wang Zhaoyin; Han Lujie; Pan Baozhu
Linked Author(s): Mengzhen Xu
Keywords: Qinghai-Tibetan Plateau; Desertification index; Blowing sand; Grain size distribution; Mineral composition; Desertification control
Abstract: Desertification is defined as the phenomenon in which aeolian soil erosion happens, causing sand dunes to form and move, and deserts form due to climate change and human activities. Desertification in Qinghai-Tibetan Plateau where is most sensitive to climate changing, has become a focus of the world' s ecological and environmental problems. Climate warming combining with anthropological activities has resulted in permafrost degradation, vegetation degeneration, sand dunes moving, and expanding of desertification in the plateau. In this study, field investigation and sampling were conducted in different active sand dunes, semi-fixed sand dunes, and fixed sand dunes for understanding the mechanism of desertification in Qinghai-Tibetan Plateau. Sediment composition of the active, semi-fixed, and xed sand dunes were analyzed to identify the component (called“blowing sand”) that playsthe most important role in resulting in desertification. Desertification index (DDI) ,indicating the risk of desertification for an area, was defined as DDI=RA×a+RSF×s+RF×f+RMS×g, in which a, s, f, g indicates the different levels of desertification risk and are assigned as 1, 0. 5, 0. 25, and 0 for the active, semi-fixed, fixed sand dunes, and grasslands, respectively; RA, RSF, RF, and RMS are the proportions of the active, semi-fixed, fixed sand dunes, and grasslands in the sampled area. The relation between the percentage composition of blowing sand in each sediment sample and the desertification index of the sampled area was examined. It was found that blowing sand mainly composed of quartz mineral particles with grain sizes of 0. 05-0. 25 mm. The desertification would hardly occur when the percentage composition of blowing sand was lower than 50%, while the risk of desertification increased quadratically as the percentage composition of blowing sand increased when the percentage was higher than 60%. Therefore, the percentage composition of blowing sand is among the most important parameters resulting in desertification. Nevertheless, vegetation coverage is essential for controlling the proportions of the active, semi-fixed, and fixed sand dunes. Strategies helpful for reducing the proportion of blowing sand and promoting vegetation coverage are recommended for prevention of desertification in Qinghai-Tibetan Plateau.
Year: 2015