延安试区人工刺槐林地的土壤干层分析

８０年代以来，以林草地地力衰退为特征的人工林草地土壤退化日趋严重，其中以土壤水分严重亏缺为特征的土壤干化现象愈益引起了人工的重视。土壤干化的的直接后果是形成土壤干层，导致土壤退化，植物生长速率减缓，群落衰败以至大片死亡，严重地威胁到我国北方地区特别是黄土高原地区生态环境的建设，因此，研究和解决土壤干层问题已成为黄土高原植被建设的迫切任务。根据延安试区的土壤水分和植被生长状况调查资料，初步分析了不同条件下刺槐人工林地的水分状况。结果表明：试区刺槐人工林地普遍形成了土壤干层，且已相当严重；坡向对土壤干层有明显影响，阳坡形成的干层阴坡严重，坡度愈大；土壤干化愈剧烈。林龄对干层严重程度影响不影响，同时，研究指出了解决土壤干层问题的意义。

The analysis to dried soil layer of artificial Robinnia pseudoscacia forestry land in the Yanan Experimental Area

Since the 1980s,the soil deterioration whose characteristic is marking the land degradation of the artificial forestry and grass lands is being worse and worse.Soil desiccation whose characteristic is critical deficit of soil moisture continuously is received much attention.Soil desiccation forms dried soil layer,results in soil deterioration,slows down the velocity of vegetation growth,causes community declination and death,and imperils seriously ecological environmental construction of the north area of China,especially in the Loess Plateau.So,studying and solving problems about dried soil layer have become the urgent task for the vegetation construction in the Loess Plateau.In this paper,according to the investigation data of soil moisture and vegetation growth in the Yanan Experimental Area,the status of soil moisture of artificial Robinnia pseudoscacia forestry land is analyzed in the different conditions.The results show that: (1) dried soil layer has been formed in the artificial Robinnia pseudoscacia forestry land and is very bad now;(2) slope direction has the significant effects on the dried soil layer,and dried soil layer in the southward slope is worse than that in the northward;(3) the greater the slope,the worse the soil desiccation;(4) forestry age has no significant effects on the dried soil layer.Meanwhile the significance of solving problems about dried soil layer is discussed.