To accurately understand and evaluate the spatial distribution of wind speed and the erosion characteristics of farm-shelter forest network in a typical strong wind environment, the research on space wind speed and surface wind erosion characteristics of farmland shelterbelts in Yanchi County, Ningxia Hui Autonomous Region in arid sandy area is carried out. The spatial distribution of wind speed within 50 and 200 cm vertical space above the ground and the erosion characteristics have been studied at the different distances from the farm-shelter forest network with portable anemometer and trapping method respectively. The result shows that: With the increase of monitoring distance, the amount of wind erosion increased first and then decreased, while the wind speed changed in the opposite direction. The wind speed changes at 50 and 200 cm height are the same, which show a very regular inverted parabolic linear change of first gradually decreasing and then gradually rising. The effect of wind reduction at 12H height (12 times shelter forest height, the same below) is the most obvious. Wind speeds decreased by 51% and 46% at 50 and 200 cm height respectively. With the increase of the distance, the wind-break potency presented the tendency of increasing at first and then decreasing. The wind-break potency was the best at the 200 cm height from 12H, and the value was 53.65%. The amount of wind erosion was positively correlated with the distance from the farm-shelter forest network. The erosion modulus in the farm-shelter forest network was the least, and the order was 1H < 12H < 3H and 7H. The value at 3H height was the biggest, 21 944.62 t/km2. The sand diameters were about 73.99, 87.99 and 104.6 μm, 82.53%-99.93% was under 248.9 μm, and the sand was the fine sand. However, the sand diameters of the bare land were about 104.6-148 μm. These reflected that the sandy irrigated farmland was the main dust source. So configurating the farm-shelter forest network scientifically and reducing the bare soil could prevent sand disaster effectively in the arid sandy area. Thus, even in the early growth of tree leaves, farmland shelterbelts in arid and sandstorm areas are also very effective in slowing wind speed during typical windy days. However, due to the rich source of sand in the forest network, the wind erosion is still serious and has a great impact on the local sandstorms. The farmland shelterbelt network is set scientifically to minimize the occurrence of wind erosion and sand damage as much as possible during the wind-affected season for farmland. This study can have certain technical reference to accurately grasp the wind erosion of the local forest network, and scientifically evaluate the forest network protection function.%为准确了解和评价干旱风沙区在典型大风环境下农田防护林空间风速分布,以及林网内风蚀状况,分别利用三杯风速仪和诱捕法,对干旱风沙区盐池县农田防护林网空间风速与地表风蚀特征开展了林网内不同水平距离内的距地表50、200 cm高度风速分布与地表风蚀状况监测.研究表明:1) 随着防护距离的逐渐增大,风蚀量呈先增加后减少的变化趋势,而风速变化规律正好相反;50和200 cm高度的风速变化规律均一致,均呈先逐渐降低后逐渐升高的变化,以12H处对风力减小作用最明显,50和200 cm高度的风速降幅分别达到了51%和46%;林带防风效益与距离呈先增加后减小趋势,以12H(12倍的防护林带树高,下同)处200 cm高度最佳,为53.65%;侵蚀模数由林带内的轻度、1H处的强度到3H、7H处的剧烈,12H处为极强度,以3H处最大,为21944.62 t/km2.2) 沙粒粒径以73.99、87.99、104.6 μm区间为主,其中82.53%~99.93%沙粒均集中在248.9 μm以下,为细沙粒,而旷野对照组沙粒粒径主要集中在104.6~148 μm,沙粒明显较粗.因此,干旱风沙区沙质农田防护林网在典型大风日内对风速的减缓非常有效.但由于林网内沙物质源丰富,风蚀现象依然严重,对当地沙尘暴发生影响较大.该研究对准确掌握当地林网风蚀,科学评价林网防护功能等有一定的借鉴作用.
展开▼
