新疆策勒沙漠-绿洲过渡带不同下垫面地表蚀积变化特征

Sand Erosion and Deposition on Different Underlying Land Surfaces in the Desert-Oasis Ecotone in Cele,Xinjiang,China

沙漠-绿洲过渡带天然植被具有良好的防风阻沙效益,对绿洲内部农田起到重要生态保护作用。在新疆策勒沙漠-绿洲过渡带流沙地、半固定沙地、绿洲边缘固定沙地6个不同植被覆盖度样地风蚀、风积变化观测基础上,结合地表风速数据,探讨流沙地、半固定沙地、固定沙地不同植被覆盖度和地形下地表风蚀风积变化特征及其影响因素。结果表明:流沙地表现出较强烈的地表风蚀;半固定沙地整体表现出强烈的地表风积;固定沙地上植被覆盖度越高、植株越高和排列方式越均匀、整体地势越低,单位面积风积量也就越大、风蚀量越小,风蚀主要发生在灌丛沙堆的上风向、侧翼、背风风向的裸低凹沙地表面,较高沙堆侧翼的地表风蚀量最大。植被覆盖度与单位面积风蚀量呈多项式或指数函数关系递减,植被覆盖度与单位面积风积量不呈函数分布,说明除了植被覆盖度外,植株类型、高度、排列方式、地形等都会对地表风积量产生一定影响。

Natural vegetation in desert-oasis ecotone have well effects in preventing and intercepting wind blown sand and have important ecological prevention function for farmland in oasis.On the basis of field observation of wind erosion and wind deposition changes over 1 quadrat of mobile sand land,1 quadrat of semifixed sand land and 4 quadrats of fixed sand land in desert-oasis ecotone in Cele,Xinjiang,China,characteristics of wind erosion and wind deposition changes and its cause over mobile sand land,semi-fixed sand land and fixed sand land were discussed with wind velocity data.Intense wind erosion occurs over surface of mobile sand land;Intense wind deposition occurs over surface of semi-fixed sand land;and the wind deposition volume will be more and wind erosion volume will be fewer in unit area when vegetation coverage and plant height are higher and arrangements pattern of plants are more well-distributed with lower landform as a whole over fixed sand land.Wind erosion mainly occurred on the surfaces of bare low sandy land in upwind and leeward areas and two flanks around nebkhas.The maximum amount of wind erosion always occurs at flank part around high nebkhas.It conforms to polynomial or exponential decreasing function relationship between wind erosion amount and vegetation coverage,and it doesn't follow any function relationship between wind deposition amount and vegetation coverage.Besides for vegetation coverage,kinds,height and arrangement pattern of plants and topography all influence wind deposition amount.