影响生物土壤结皮在沙丘不同地貌部位分布的风因子讨论

Discussion on Wind Factor Influencing the Distribution of Biological Soil Crusts on Surface of Sand Dunes

生物土壤结皮广泛分布于干旱和半干旱区,它的形成和发育对荒漠生态系统修复过程产生重要的影响。采用野外观测的方法,测定了固定沙丘纵断面表面气流和生物土壤结皮的发育特征。结果发现,近地表气流在迎风坡坡脚部位最低,丘顶最高,从坡脚到丘顶呈增加的趋势。近地表气流在背风坡中上部急剧下降,中下部位有所增加,到坡脚部位又呈减少的趋势,但后者均远低于丘顶的风速。各观测点不同高度风速放大率不尽相同。生物土壤结皮发育特征的测定结果显示,其厚度、抗剪强度和细颗粒物含量均从沙丘底部向中上部呈减少的趋势,表现出风速较高区域生物土壤结皮的发育程度较低,风速较低区域生物土壤结皮的发育程度较高的特点,说明生物土壤结皮在沙丘不同地貌部位的分布与由地形差异导致的气流变化之间具有密切的关系。

Biological soil crusts are widespread in arid and semi-arid areas,and their formation and development have significant effects on rehabilitation process of desert ecosystem.Air flow pattern and developmental characteristics of biological soil crusts on fixed sand dunes are studied by field observation method.Results indicate that near surface air flow on windward slope of sand dunes shows an increasing trend from the base to the top and reaches the highest point at the crest.At lee side,although near surface air flow has a little increase at lower part of the slope after initial sudden decrease at upper part of the slope,but its overall trend turns up to decreasing from the crest.Wind velocity variation coefficient is varied at different heights over each observation site.The thickness,gear strength and percentage of fine particles of biological soil crusts decrease from the base of slope to the upper part,showing biological soil crusts are less developed in high wind speed area and well developed in low wind speed area.This indicates that change of airflow pattern caused by topography could be the key factor affecting the distribution of biological soil crusts at different location of sand dunes.