Ecological Significance of the Sand Wedge In the Extra-Arid Gobi Area
2014
Li, Hong-Shou | Wang, Wan-Fu | Ma, Jian-Hong | Wu, Fa-Si | Zhan, Hong-Tao | Qiu, Fei
The sand wedge was widely found, by field survey, to lie within the Gobi on the top of the Mogao Grottoes. The characteristics of its shape, size, structure, and ecological function were investigated. This original sand wedge was of a special type; formed in an arid environment, and with a multi-level fractal structure. The width range of main wedge was from 30 to 60 cm and its depth was about 50 cm, where the width of the irregular polygon matrix was about 60 to 160 cm. Meanwhile, the features of this sand wedge, including mechanical composition, salinity, and water content differed greatly from its matrix. The salt content in the sand wedge was 0.86 g · kg ⁻¹, correspondingly, that of the matrix reached 4.56 g · kg ⁻¹. The sand wedge can absorb plentiful rainfall and retain it for a long time, which can benefit plant survival. However, the higher salt content of the matrix would dissolve under eluviation, which plays an important role in pruning roots. These double functions of higher water content in the wedge and salt pruning in the matrix have made the main roots of vegetation grow inside the sand wedge only. Thus, the net shape structure of sand wedge was vital to vegetation distribution in the Gobi and the formation of the associated geomorphologic landscape. At the same time, the sand wedge formed a crucial habitat for small animals, thus was the last surviving such enclave in the extreme aridity of the Gobi ecosystem.
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