Effects of an oasis protective system on aeolian sediment deposition: a case study from Gelintan oasis, southeastern edge of the Tengger Desert, China

Desert-oasis ecotones are boundary areas between oases and desert ecosystems. Large efforts to control sediment and stabilize these boundaries depend on understanding sedimentary processes, especially aeolian transport and deposition. Previous studies on aeolian sediment deposition have focused primarily on a single land surface type or a single engineering approach. Few studies have considered deposition in a multi-layer oasis protective system. A complete oasis protective system consists of an outer bare sand area, a sand barrier zone, a shrub and herbaceous plant zone, and a farmland shelter zone. This study used sedimentary analysis to quantify grain-size characteristics in samples from the four land surfaces under different types of weather conditions in the Gelintan oasis of the Tengger Desert, the fourth largest desert in China. The results showed that aeolian sediment deposition decreased from the outer bare sand area through the oasis protective system and into the interior. The four land surface types showed significant differences in deposition volume (P<0.05). Deposited sediment showed gradual decrease in dominant grain-size from sand to silt, but sediment deposited during dust weather contained a larger coarse-grained fraction. From the outer desert to the inner oasis, transport mechanisms shifted from saltation (sand) to suspension (silt and smaller) in non-dust weather. During dust weather, deposition primarily occurs from near-surface aeolian sand transport with saltation. Sediment sorting decreased from exterior to interior zones of the protective system while skewness and kurtosis showed no significant change (P<0.05). These results can help inform strategies for stabilizing and protecting desert-oasis ecotones in this region and other localities.