黄土区深层土壤干燥化与土壤水分循环特征  

Desiccation of deep soil layer and soil water cycle characteristics on the Loess Plateau

作　　者：陈洪松[1] 邵明安[2] 王克林[1] 

机构地区：[1]中国科学院亚热带农业生态研究所 [2]中国科学院地理科学与资源研究所

出　　处：《生态学报》2005年第10期2491-2498,共8页Acta Ecologica Sinica

基　　金：国家自然科学基金重大研究计划资助项目(90102012);中国科学院知识创新工程领域前沿资助项目(01200220055413)~~

摘　　要：深层土壤干燥化是黄土高原地区植被建设过程中出现的重大生态环境问题.采用人工和天然降雨试验,研究了黄土高原沟壑区荒草地和裸地的土壤水分循环特征,并分析和探讨了深层土壤干燥化的成因.2002年天然降雨量为459.9mm(多年平均降雨量为584.1mm),属干旱年,土壤水分观测期间(2002年6月13日至11月24日)天然和人工降雨试验小区的天然降雨量分别为305.2mm和236.8mm.人工降雨试验主要在2002年6～8月进行,土壤水分观测期间荒草地和裸地的人工降雨量分别为360.7mm和418.5mm.试验结果表明:干旱年,荒草地和裸地土壤储水量处于负补偿,入渗雨量全为蒸发蒸腾作用所消耗.在强烈的蒸发蒸腾作用下,剖面内(0～200cm)土壤水分的整体移动性能较强,最大蒸发蒸腾作用层深度很快形成.荒草地土壤水分循环强度大于裸地,表现为荒草地最大蒸发蒸腾作用层深度较大,两者分别为200cm和180cm.雨季量少且分散的降雨极易为强烈的蒸发蒸腾作用所消耗,深层土壤由于缺乏降雨入渗的补给而逐渐干燥化.丰水年,荒草地和裸地土壤储水量处于正补偿,但入渗雨量的大部分(80%以上)为强烈的蒸发蒸腾作用所消耗.在相同的降雨量条件下,荒草地土壤水分循环强度高于裸地,表现为荒草地降雨入渗补给深度较小.连续降雨有利于土壤水分向深层的运移,从而部分缓减深层土壤的干燥化进程.近50a来黄土高原地区气候变暖和降雨减少可能是土壤干层形成的直接原因,而植被类型选择失当、群落密度过大和生产力过高则会加剧深层土壤的干燥化进程.As the result of the excessive depletion of deep soil water by plants, the desiccation of the soil layer below the depth of rainfall infiltration （about 2 m） occurs widely in the Loess Plateau, particularly under artificial grassland and forestland, and thus influences the survival of the plants. However, the interactions between the development of the desiccation and water cycle in the soil layer have little understood. In the region, field investigations were carried out under grassland at a selected watershed in a gully region between June and November in 2002. The field site was divided into two areas, which received either natural rainfall or artificial rainfall. Each of them was subdivided into 2 plots （3 m × 20 m）, one remained under native grass, and in the other grass was cleaned up. The slope gradient was about 70% for the plots receiving natural rainfall and 57.7% for those receiving artificial rainfall. The total amount of natural rainfall in 2002 was 460 mm, less than the annual average rainfall of 584 mm by 21%. During the investigation period （June 13 to November 24 in 2002）, natural rainfall was 281 mm （equivalent to 230 mm as slope surface） in the former plots and 237 mm （equivalent to 205 mm as slope surface） in the latter. The areas received extra 419 mm （equivalent to 363 mm as slope surface） water for plot where grass was cleaned out and extra 361 mm water （equivalent to 313 mm as slope surface） for the plot with grass, as artificially simulated rainfall. Water content in soil layer of 0 - 3m or 0- 4m was determined using a neutron probe every 1 or 2 weeks during the investigation period. Results obtained demonstrated that the total amount of water in the soil profile of 0- 3 m in the plot under native grass and natural rainfall decreased from 460 mm at the beginning to 411 mm by the end of the investigation period （June 14 to November 24 in 2002）. The corresponding decrease in soil water in the plot under natural rainfall but without grass coverage was measu

关 键 词：黄土高原 坡地 土壤干层 土壤水 循环 

分 类 号：S152.7[农业科学—土壤学] S154.1[农业科学—农业基础科学]