浑善达克沙地不同植被下的土壤水分状况

浑善达克沙地的中东段阳坡近裸的流动风沙土 0 - 1 0cm土层整个生长季内平均含水量较低、波动也比较大 ,而在 1 0cm以下则基本稳定在 3%左右 ,尤其是深层。丘间低地草本群落下的土壤湿度随深度增加变化较大 ,2 0cm以上土层含量较高 ,40 - 5 0cm土层的含水量最低 ,波动也剧烈 ,90cm以下达裸沙含水量水平。阴坡灌丛下 ,最低土壤含水量出现在 70 -90cm土层 ,深层土壤含水量长期稳定在 1 .5 %左右。这说明植物的生长使根层土壤含水量下降 ,而且不同植物利用水的土层及利用土壤水的量不同。这可能是引起流动风沙土向固定风沙土转变过程中地表植被演替及决定地区顶级群落的主要原因。在干旱半干旱地区 ,植被影响着降水在土层中的分布及地表的蒸散条件 ,使土壤有效水向浅层分配。而降水在土壤不同深度的分配及入渗深度 ,决定着地表植被的生活型 ,从而影响地表植被的演替方向及顶级类型。需水量较大的灌丛在沙丘阴坡能形成稳定的群落 ,是由于沙丘为植物避免干旱胁迫 ,延长在干旱季节的生存时间创造了条件 ,因此 ,沙丘是沙地的重要环境资源 ,尤其是高大沙丘 ,在这类地区的防风固沙中具有重要的作用。

Soil Water Regime Under Different Plant Coverage in Hunshandake Sand land

A study on soil water regime under different plant coverage was carried out in the east of Hunshandake sand land. The results show that the soil water content in 0-10cm layer of nearly bared mobile aeolian sandy soil fluctuates intensively, and the average soil water content through the whole growth season is very low. That in the soil deeper than 10cm is about 3% through the whole growth season ,and is relatively stable. The soil moisture is for scrub absorbing mainly in the depth from 30 cm to a depth of lower than 110 cm. The soil moisture for herb is mainly in the layer of 20-90 cm. In the arid and semiarid region, plant decreases the depth of rainfall-moistened layer in soil. The available soil water distributes to shallow layer. And the distribution of rainfall in soil profile and the depth of rainfall-moistened soil confine the plant rhizotaxis, and determine the direction of vegetation succession and the type of climax community. As a feedback regulator, soil water makes the vegetation in arid and semiarid region become negative feedback system. The high sand dune may be an important environmental resources for plant to escape drought in the arid and semiarid region.