河西走廊沙区沙面稳定性指标的观测研究

民勤、武威-古浪、临泽3个沙区9个指标的研究结果表明,沙面稳定性主要与植被盖度、≤0.074mm细沙土含量、0.3~0.1mm中细沙含量及>0.5mm粗沙含量有关;0.3~0.1mm的中细沙是沙面中最不稳定的因素,≤0.074mm细沙土主要为粘土成分。沙面稳定及活化的组合作用主要是以细沙土与植被盖度为代表的固化作用和以细沙土为代表的固化作用以及以0.3~0.1mm中细沙为代表的活化作用;临泽、武威-古浪沙区较民勤沙区不易固定的原因主要是活动性大的中细沙显著多于粗沙;于降水前在沙面上施撒粘土可大面积固定沙丘,尤其在水分条件限制造林密度不易过大或造林难以成活的重沙害区是一种有效的固沙措施。

Indexes of Sand Surface Stability in Hexi Corridor

Research results from 9 indexes in Minqin, Linze and Wuwei Gulang desert areas show that the sand surface stability is mainly correlated with vegetation coverage, fine sand grain (dia. ≤0.074 mm) content, medium sand grain (dia. 0.1~0.3 mm) content, height of sampling position, and coarse sand grain (dia. 0.5 mm) content. The higher the vegetation cover and the fine sand grain content as well as the coarse sand grain content is, the more stable the sand surface is. The medium sand grain content and height of sampling, the unstablest factors, are correlated with the sand surface stability negatively; The fine sand grain content, mainly composed of clay, is correlated with the sand surface stability positively. The combinating functions mainly are that: (1) take fixed area, fine sand content, and vegetation cover as positive factors but height of sampling position and medium sand content as negative factors; (2) take medium sand content, fine sand content, vegetation cover as positive factors but 0.3~0.5 mm sand content as a negative fator; (3) take 0.074~0.1 mm sand content as a positive factor; (4) take height of sampling position and 0.3~0.5 mm sand content as positive factors but 0.074~0.1 mm sand content as a negative factor; (5) take soil density of sand surface and vegetation cover as positive factors but coarse sand content as a negetive factor. On the average, if the area of fixed sand surface is required to be 100%, the vegetation cover in Xishawo of Minqin has to reach 30.9%, that in Xiaoquanzi of Linze to reach 38.5%, and that in Wuwei Gulang to reach 40.6%; if the area of fixed sand surface is required to be 80%, the vegetation cover in Xishawo has to reach 25.0%, that in Xiaoquanzi to reach 32.6%, and that in Wuwei Gulang to reach 34.7%; if the area of fixed sand surface is required to be 50%, the vegetation cover in the above regions has to reach 16.2%, 23.8% and 23.0% in order. The research results show that adding clay to the sand surface is an effective way to stablize the surface, particularly suitable for the area with hush natural conditions and serious damage from shifting sand. In the Hexi area, a 6%~7% clay content in the sand surface can lead to the formation of crust on it. Scattering clay on the surface before raining can help the crust formation.