Aeolian sand, desertification and restoration strategies in Qinghai-Tibetan Plateau

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Mengzhen Xu, Yanfu Li, Zhao-Yin Wang, Lujie Han, Baozhu Pan

Tuesday 30 june 2015

17:15 - 17:30h at North America (level 0)

Themes: (T) Extreme events, natural variability and climate change, (ST) Hydrological extremes: floods and droughts

Parallel session: 7I. Extreme events - Flood Drought

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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, semifixed sand dunes, and fixed sand dunes for understanding the mechanism of desertification in Qinghai-Tibetan Plateau. Sediment composition of the active, semifixed, and fixed sand dunes were analyzed to identify the component (called “aeolian sand”) that plays the most important role in resulting in desertification. Desertification index (DI), indicating the risk of desertification for an area, was defined as DI=A%×Ra+S%×Rs +F%×Rf, in which Ra, Rs, Rf are the levels of desertification risk and assigned as 1, 0.5, and 0.25 for the active, semifixed, and fixed sand dunes, respectively; A%, S%, F% are the proportions of the active, semifixed, and fixed sand dunes in the sampled area. The relation between the percentage composition of aeolian sand in each sediment sample and the desertification index of the sampled area was examined. It is found that aeolian sand mainly composed of quartz mineral particles with a size of 0.05 to 0.25 mm. The desertification would hardly occur when the percentage composition of aeolian sand was lower than 50%, while the risk of desertification increased exponentially as the percentage composition of aeolian sand increased when the percentage was higher than 60%. Therefore, the percentage composition of aeolian sand is among the most important parameters resulting in desertification. Nevertheless, vegetation coverage is essential for controlling the proportions of the active, semifixed, and fixed sand dunes. Strategies helpful for reducing the proportion of aeolian sand and promoting vegetation coverage are recommended for prevention of desertification in Qinghai-Tibetan Plateau. Keywords: Qinghai-Tibetan Plateau, desertification index, Aeolian sand