甘肃民勤绿洲边缘积沙带形成的气候环境因素及其生态效应

In northwest China, many efforts have been made in desert control in the past 50 years. Subsequently, an accumulated sand belt at the oasis fringe was taken shape. The accumulated sand belt is a by-product in desert control effotrs. What factors are influencing its development? Is it stable? How about its ecological effect - that is to say, is it useful to improve the environment in the desert or it will induce more serious ecological issues? These are not only scientific issues, also imperative problems need to be solved in the practice. However, there are few studies in this field in China. This study will be conducted in Minqin oasis, one of the areas where desert control activities were initially implemented. Over 10 sample sites will be selected on the accumulated sand belts at Minqin oasis fringe. With the help of local meteorological data and satellite imagery, 3 problems will be studied: (1)the correlation between the increment of the accumulated sand belts and the climatic factors; (2) stability of the accumulated sand belt; (3) the ecological effects of accumulated sand belts. The solutions to these problems will conducive to enrich the systematic construction of desertification combating in China, and also be of realistic significance in assessing the available and future desert control measures.

我国西北沙区经过半个多世纪的防沙治沙，在绿洲边缘形成了积沙带。积沙带作为绿洲边缘防沙固沙的副产物，其发育的速率主要与哪些因素有关，其稳定状态如何，又具有怎样的生态效应，即积沙带的形成是有利于沙区生态环境的改善，还是会导致更加严重的生态问题呢。这既是一个科学问题，也是一个防沙治沙实践中亟待解决的现实问题。然而，截止目前国内外尚缺乏有关积沙带的研究。本项目以我国防沙治沙历史较早的典型沙漠化地区民勤绿洲边缘积沙带为研究区，在积沙带上选定10多个样点进行调查观测，并结合当地气象和航片资料，研究：1）绿洲边缘积沙带的堆积速率与气候环境因子的关系；2）积沙带的稳定性；3）积沙带的生态效应。这一问题的解决有助于充实完善沙漠学科和防沙治沙学科体系建设，对于评价现有的防沙治沙措施以及选择防沙治沙措施也具有重要的现实意义。

我国西北沙区经过半个多世纪的防沙治沙，在绿洲边缘形成了积沙带。积沙带作为绿洲边缘防沙固沙的副产物，其发育的速率主要与哪些因素有关，其稳定状态如何，又具有怎样的生态效应。甘肃民勤绿洲边缘的积沙带分布最连续，相对较高大。因此，本课题以甘肃民勤为研究区，通过选定观测样点，测定积沙带的高度、宽度、沙面土壤粒度、植被调查、流场观测，以及与甘肃河西走廊沙区积沙带对比，从绿洲边缘积沙带的堆积速率与气候环境因子的关系、积沙带的稳定性以及积沙带的生态效应三个方面研究了甘肃民勤绿洲边缘积沙带形成的气候环境因子及其生态效应。研究结果表明：1）民勤绿洲边缘积沙带按形成方式可分为天然灌丛积沙带、乔木林带积沙带、人工固沙林积沙带三种，其中天然灌丛形成的积沙带相对高大，而农田边缘单纯的乔木林带形成的积沙带最窄。2）控制积沙带高度的环境因子主要是积沙带与主风向的夹角，即积沙带与主风向的夹角越小，则积沙带的高度越低。上风向对准风沙口时，则积沙带与主风向的夹角越小，积沙带的宽度亦越窄。3）积沙带作为绿洲边缘防沙固沙的副产物，其自身也具有防风阻沙的功能，积沙带的形成有利于绿洲边缘的防风阻沙。4）高度是表征积沙带防御风的功能的一个重要指标，积沙带越是高大，防御风的范围就越大。5）目前，河西绿洲边缘积沙带处于发育状态。只要控制了积沙带就能有效控制流侵入农田。今后应将绿洲边缘防沙治沙的重点放在积沙带上，尤其是积沙带的沙脊线上，而对荒漠—绿洲过渡带（阻沙带）实行封育，无需采取其他投入措施，这样就可以大面积压缩实施人工措施的范围，大大降低防沙治沙的资金投入，提高防沙治沙的投资效益。