关键词: 沙棘造林, 防风固沙, 风速增加幅度, 风沙流结构

Abstract: Hippophae rhamnoides is a pioneer species of controlling desertification with strong ecological improvement and adaptability. Since 2008 when the measure of Hippophae rhamnoides forestation was firstly implemented in Ketu sandy land in the east of Qinghai Lake，the areal wind-sand activities and hazards have been obviously decreased，but the functional mechanism and promoting feasibility of this measure in the high-altitude and climate-cold areas need a far-researching and brief evaluation. Through a series of field wind-sand and vegetation observations in each spring of 2010，2011 and 2012，the wind-profiles and wind-flow structures of both H. rhamnoides dune and mobile dune could be compared，and mainly analyzed the mechanism and benefits of wind-prevention and sand-fixation by rhamnoides under some statistics of wind speed amplification，surface roughness，sand transport，etc. Firstly，the logarithmic law of wind-profile of the rhamnoides dune was totally broken，and as well as the exponential law of sediment discharge and sand-grain size distributing with the height，those were reflected by a higher wind increasing rate in the low and middle layers，an increasing percentage of sand transport in the upper layer，and a major distribution of coarser grain in the middle layer，which all were basically caused by the vertical lifting function of air flow and air energy accumulation in the plant canopies. Secondly，the benefit of [H. rhamnoides] wind-prevention changed with the height and the year. The wind-prevention function of the low layer is 2.0-3.7 times that of the middle layer，and 4.0-7.2 times that of the upper layer. Moreover，the average wind-prevention effects under the height of one meter increased to 22.75% in 2012 over twice as many as in 2010. Also，the benefit of [H. rhamnoides] sand-fixation increased yearly which is about 80% in 2010 and 88.9% in 2012 under a wind speed of 10 meters per minute. Thirdly，the two benefits would decrease slowly with the increasing of the wind velocity，but get raised yearly with the vegetation height and canopy，and the area and thickness of the crust would propel to a more significant benefit of preventing the wind erosion. Actually，with the protection of straw-checkerboards，the survival or preserving rate of H. rhamnoides would get improved and take better effects of preventing wind and sand hazards，however，some new attentions should be transferred to the forestation density in different landforms and soil properties for better ecological functions. Under those comprehensive study of controlling process and benefits，the technique of Hippophae rhamnoides forestation was conclusively applied to the work of controlling desertification in Ketu sandy land，even more，it was valuable to extend the measure to the whole alpine region.

Key words: Hippophae rhamnoides forestation, wind-prevention and sand-fixation, wind increasing rate, wind-sand flow structure