中文摘要：

以丰水年洛川人工林地深层土壤水分恢复为依据，采用高精度土壤含水量测量与逐层分析技术，以含水量变化率为主要指标，研究洛川2004年1月-2005年5月不同植被土壤水分的季节变化与水量平衡。结果显示，降水渗深以内表层土壤水分受气候和植被生长影响，呈明显季节变化；渗深以下深层土壤水分，中产农田和梨树林砍伐后基本维持平衡，苹果林地持续减少并以春季减少最多。研究表明，黄土高原深层土壤水分呈低水平循环状态，易形成土壤干层，而季节干旱是土壤干层形成的直接驱动力；“低降水、高蒸发”的气候特点是黄土高原土壤干层形成的决定因素，半湿润半干旱气候中的干旱特征对黄土高原自然地理环境产生广泛而深刻的影响。

英文摘要：

According to the recovered soil moisture content in deep soil layers in Luochuan in rainy year, which has been measured by high precision measurement and analyzed layer by layer, the change of soil moisture content under different artificial vegetation in different seasons was studied from January 2004 to May 2005. The result shows that the soil moisture content of surface layer changed obviously with season which was caused by climate and plant growing. It is also shown that the soil moisture content was stable of deep layer under farmland or land once planted pear trees,while it was decreasing continually under apple trees. It can be known that the deep soil moisture content cycles in a low level,which tends to breed dried soil layer in the Loess Plateau. What＇s more, the direct inducement of dried soil layer is seasonal drought. So ＂less rainy, higher evaporation＂ climate is the decision factor that causes dried soil layer. The drought character of semi-humid and semi-arid climate affects the natural geo-environment of Loess Plateau deeply and widely, which should be paid special attention when we take measures in the Loess Plateau.