定西龙滩流域不同人工植被类型土壤水分动态研究

通过对定西市安定区龙滩流域7种人工植被类型（柠条林、油松林、侧柏林、山杏林、退耕紫花曹蓿地、退耕隔坡林地、农田）20个野外样点的土壤水分定位观测，研究了不同植被类型土壤水分动态变化规律。结果表明：1）不同植被类型间土壤水分具有显著性差异；2）坡位并非是影响该流域土壤水分变化的显著因子；3）坡度对土壤水分的影响以25°为具有显著性差异的分界点；4）土壤水分垂直层次可划分为土壤水分的弱利用层、主要利用层和调节层；5）剖面土壤水分的变异系数地表（0～20cm）最大，0～140cm土层呈递减趋势，140～200cm土层基本保持“恒定”，120～140cm土深为土壤水分速交层和稳定层的分界线。

Study on Soil Moisture Dynamics of Different Artificial Vegetation at Longtan Watershed in Dingxi

By monitoring soil moisture at 20 field spots, the studies were carried out on the soil moisture dynamic change law of 7 kinds of artificial vegetation cover types including caragana-land, pine-land, arborvita-land, al-mond- land, alfaalfa-land, level trench land, and crop-land in Lonftan watershed of Dingxi city. The results showed ： 1） there is remarkable difference between different vegetation cover types on soil moisture; 2） the variation of soil moisture between the top, middle and bottom slope is not remarkable; 3） the 25° grade of slope is the division between the remarkable variation and the fluctuate variation on soil moisture; 4） the soil profile would be divided into three layers including weak utilization layer, utilization layer, and regulating layer; 5） the variation coeffi-cient of soil moisture is the biggest in the surface layer （0-20 cm） in the profile, while the layer between 0-140 cm pre-sents to decreasing trend, in the 140-200 cm soil layer keeping constant basically, so 120-140 cm can be defined as a limited boundary between the quickly changing layer and the stable layer of soil moisture