通天河七渡口位于长江上游楚玛尔河和通天河交汇处,属于长江的水源涵养区和补给区,近年来该地区草场在风力侵蚀作用下出现沙漠化趋势。为控制沙化草地的进一步蔓延,我们在通天河七渡口进行了风沙环境观测,并开展了机械和植物固沙试验。结果表明:通天河七渡口年平均风速为1.95 m·s-1,最大风速20.63 m·s-1,主起沙风向为偏西风(包括W、WSW、WNW),次起沙风向为东北风(包括NNE、NE),年输沙势为93.06 VU,年合成输沙方向为107.54°,年总输沙量为3 007.30 g·cm-1。经过两年的机械和植物固沙试验,沙障内形成了稳定的蚀积凹曲面,使沙层表面得到固定,有效控制了沙丘移动。随着沙障内人工植被的逐渐生长,试验区内地表微环境逐渐得到改善:(1)土壤颗粒变细,沙样粒径组分中粉沙和黏土增多,沙障内未种草地和沙障内人工种草地粉沙和黏土含量分别是流沙地的6.4倍和9.1倍;(2)表土有机质增多,流沙地、沙障内未种草地、沙障内人工种草地表土有机质含量分别为0.91、1.48、2.02 g·kg-1;(3)沙层表面形成土壤结皮,土壤硬度增强,流沙地、沙障内未种草地、沙障内人工种草地土壤硬度分别为0.52、1.25、2.12 kPa。
Qidukou is located in the confluence reaches of Chumaer River and Tongtianhe River and belongs to the headwaters of Yangtze River. In recent years, the temperature increased in Qinghai-Tibet Plateau, and the climate changed to aridity in the source region of Yangtze River. In addition, high and over grazing made the problem of grassland desertification presented in Qidukou, Tongtian River. To control the further spread of the desertification grassland, we have observed characteristics of the wind-blown sand environment, and have made a mechanical and plant sand-fixation experiment in this region. The observation results showed that the annual-average wind speed was 1.95 m·s-1, the maximum instantaneous wind speed was 20.63 m·s-1, the direction of prevailing sand-moving wind was westerly wind (include W, WSW and WNW), the annual sand drift potential was 93.06 VU, the sand transport direction was 107.54°, and the annual sand transport amount was 3 007.30 g·cm-1 in Qidukou, Tongtian River. After two years of mechanical and plant sand-fixation experiment, concave curved surfaces formed in the HDPE sand barriers, which made the sand bed fixed, and controlled the dune movement effectively. As the growing of artificial vegetation in the sand barriers, the soil microenvironment in the experimental zone improved gradually:(1) Silt and clay content increased in HDPE sand barriers without/with artificial vegetation, it was 6.4 and 9.1 times more than that in drift sand. (2) Organic content increased, which was 0.91, 1.48, 2.02 g·kg-1 in drift sand, sand barriers without artificial vegetation, and sand barriers with artificial vegetation respectively. (3) Soil hardness increased, which was 0.52, 1.25, and 2.12 kPa in drift sand, sand barriers without artificial vegetation, and sand barriers with artificial vegetation respectively.
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