河北坝上低山区坡地灌丛沙堆形态与沉积特征

Morphology and Sediment Characteristics of Nebkhas on Slopes in Bashang Region,Hebei Province

通过野外调查和室内试验分析的方法对河北坝上康保县北部低山区坡地小叶锦鸡儿(Caragana microphylla Lam.)灌丛沙堆形态及沉积特征进行了研究,结果表明:从坡顶到坡脚,灌丛沙堆形态参数(长、宽、高、水平尺度、长宽比和底面积)趋于增加;迎风坡坡顶、坡中、坡脚的灌丛沙堆形态参数大于背风坡相应坡位沙堆形态参数;从坡脚到坡顶,沙堆表层沉积物粒径(>0.1mm)的百分含量趋于减少,坡地迎风坡相应坡位沙堆沉积物粒径>0.1mm的百分含量大于背风坡;灌丛沙堆表层土壤含水率及硬度从坡脚到坡顶逐渐变大,坡地迎风坡坡相应坡位沙堆表层土壤水分和硬度均小于背风坡;而容重从坡脚到坡顶趋于减小,且迎风坡坡相应部位沙堆容重大于背风坡。因此,低山坡地灌丛沙堆形态发育过程中除受风力强度、沙源和灌丛植被因素影响外,坡位和坡向也是一个重要的影响因素。

The morphology and sediment characteristics of nebkhas on slopes were studied by means of field observation and sampling in Bashang region,Hebei Province.The results show that：（1）from the top to the foot of the investigated hills,the morphology parameters of nebkhas gradually increase,and the morphology parameters of nebkhas for the windward slope is greater than those for the leeward slope;（2）from the foot to the top of the investigated hills,the percentage of the coarse grain（diameter〉0.1mm）of the surface sediments of the nebkhas gradually decreases,the percentage of the coarse grain（diameter〉0.1mm）of the surface sediments in the windward slope is greater than that in the leeward slope;（3）from the foot to the top of the investigated hills,the surface soil moisture and the soil hardness of the nebkhas become greater,and the surface soil moisture and hardness of the windward slope are less than those of the leeward slope;（4）from the foot to the top of the investigated hill,the bulk density becomes less,and the bulk density of the windward slope is greater than that of the leeward slope.In addition to the three main factors of cover,wind strength,and sand,the site condition is an important factor which influences the formation and evolution of nebkhas on slopes.