3种机械沙障防风固沙功能的时效性

对设置在民勤治沙综合试验站固定沙丘地带的3种机械沙障(麦草沙障、粘土沙障、塑料网格沙障)在不同时期进行破损率、输沙率、风速等指标的测定,研究经过不同时间后各类沙障的防风固沙效益。试验结果表明:各类沙障设置初期(2002-2004年)均具有良好的防风固沙效果,但是随着时间的推移,各类沙障破损率均有所增加,6年后麦草沙障的破损率最大,平均为53%,塑料沙障最小,为11%,粘土沙障介于二者之间;沙障破损导致地表粗糙度均发生明显的变化,麦草沙障由设置初期粗糙度最大降到了最低,其近地表层0～20cm处的输沙率由2003年占裸地(CK)的0.11%上升为2009年的44.47%;粘土沙障顶部掏蚀严重,其输沙率也随时间的延长呈增加趋势,由19.32%上升为30.87%,这两类沙障表面由固定向流动沙丘发展的趋势明显。塑料沙障中下部沙面稳定而顶部很少被掩埋,平均粗糙度最大,其输沙率随时间的延长呈减少趋势,由2003年占裸地(CK)的2.73%下降为2009年的0.64%,表明沙障内沙面稳定,沙丘基本固定住,沙障仍具有固沙效应。从设置成本和实际的防护效益等方面综合考虑,塑料沙障相比其他机械沙障具有长期、稳定的生态和经济效益。

Timeliness of Reducing Wind and Stabilizing Sand Functions of Three Mechanical Sand Barriers in Arid Region

Based on the indexes of wild observation such as breakage rate,sand transport rate,wind velocity,etc.on three different mechanical sand barriers including wheat straw barriers,clay sand barriers and plastic checkerboard sand barriers located at Minqin Desert Control Experiment Station,effects of wind reducing and sand fixing of these three kinds of sand barriers which were subjected to different times had been studied,the results showed that each kind of barriers had good effects of ecological functions when they had been built at beginning,the wheat straw sand barriers were the greatest effects of reducing wind speed and stabilizing sand among all kinds of barriers,the sand fixing effect of the plastic barriers was followed,and that of the clay sand barriers was the lowest.But,the breakage rate of these barriers increased with the times elapsed.After 6 years past,the average breakage rate of the wheat straw barriers was 53%,the plastic barriers was 50% and the clay sand barriers was 11%;meanwhile,the roughness rate of these barriers also obviously decreased with changing of breakage rate,and the sand transport rates occurred at near-surface height of 0~20 cm located in the different sand barriers were varied with changing of sand barriers’ roughness rate.The roughness rate of wheat straw barriers was the highest in the setting early,but down to the lowest after 6 years,the percentage of compared CK of sand transport rate was increased from 0.11% in 2003 to 44.47% in 2009,respectively;the top of clay sand barriers erode severely,its sand transport rate was the same as changing of that of wheat straw barrier,the percentage of compared CK increased with the extension of time from 18.32% to 30.87%.It was indicated that trends of these two barriers were developing from fixed sand dune to moving sand dune.The average roughness rate of plastic sand barriers was the highest among three kinds of barriers,and its sand transport rate was declined from 2.73% which was compared with CK in year of 2003 to 0.64% in 2009,it showed that plastic sand barriers had fixed the moving sand dune which of the surface was in a stable state.Above those results,based on some factors such as costs,practical application and value analysis of each kind of sand barriers in 2003 and 2009,it would been inferred a conclusion that the plastic sand barriers had longer service time and better stabilizing sand effect than others,although its cost was higher at early stage construction.