关中平原黄土中第1层古土壤发育时的土壤水分研究  

Research in Soil Moisture during Development of S_1 Paleosol in Guanzhong Plain

作　　者：赵景波[1,2] 罗小庆[1] 刘瑞 陈宝群[1] 岳应利[1] 

机构地区：[1]陕西师范大学旅游与环境学院,西安710062 [2]中国科学院地球环境研究所黄土与第四纪地质国家重点实验室,西安710075 [3]武警工程大学,西安710086

出　　处：《地质学报》2015年第12期2389-2399,共11页Acta Geologica Sinica

基　　金：陕西省自然科学基础研究计划项目(2015JM4135);国家自然科学基金国际合作重大项目(41210002);中国科学院黄土与第四纪地质国家重点实验室项目(SKLLQG1428)资助

摘　　要：根据关中平原西安地区和宝鸡地区调查和实验分析资料,研究了该区黄土中第1层红褐色古土壤发育时的土壤有效水含量、重力水分布、水循环和水分平衡等问题。结果表明,该层古土壤CaCO_3与元素Sr迁移深度达到了4.2m,位于古土壤黏化层底界之下的风化黄土层发育厚度为2.2m,淋滤裂隙发育深度为3.9m,Fe_2O_3含量较高的红色铁质黏土胶膜迁移到了土壤黏化层底界之下约1m深处的黄土中,迁移到了4.2m深处的CaCO_3结核中方解石结晶良好。这些指标显示,在西安和宝鸡地区该层古土壤发育的最温湿阶段,土壤重力水带分布深度至少达到了4.2m,当时该区4.2m深度范围内土层水分充足,在植被生长季节和每年绝大部分时间里土层平均含水量一般为22%左右,在蒸发与植被吸收、树冠截留以及地表径流损失之后剩余的可利用有效水含量为14%左右,当时土壤水分充足,没有土壤干层发育,能够满足茂盛森林植被发育的需要。西安和宝鸡附近S_1古土壤发育时的最湿润时期土壤重力水带分布深度比现今大2m左右,土壤水是酸性的。在关中平原S_1古土壤发育时,土壤水分的收入量大于支出量,土壤水分为正平衡,土壤水循环正常,每年雨季一般有较多的水分通过土壤入渗补给地下水,这也是当时土层含水量高的原因。关中平原与洛川等地2003丰水年的重力水分布深度与含水量证实了S1古土壤发育时的土壤水研究结果是可靠的。多项指标显示,在S_1古土壤发育的最温湿阶段,夏季风气团能够频繁越过秦岭山脉到达关中平原地区,秦岭南北均为亚热带气候,这表明当时秦岭失去了温带与亚热带气候分界线的作用。S_1古土壤发育过程经历了5万余年的漫长时间,在最温湿阶段之外的其它阶段,发育森林草原等植被是可能的。本项研究确定的土壤古水分水指标对国内外的研究有重要应用价值。Based on field investigation in the Guanzhong plain and Baiji area,this study analyzed available water content,distribution of gravity water,water cycle and balance in the first paleosol layer（S1）using laboratory analysis.The results show that the migration depth of CaCO3 and Sr is up to 4.2m.The development thicknesses of weathering loess under the bottom of argillic horizon and leaching fracture are2.2mand 3.9mrespectively.The migration depth of red ferruginous clay adhesive film rich in Fe2O3is 1 munder the bottom of argillic horizon.The crystal calcite of CaCO3 concretion is well developed.These indexes indicate that the developmental condition of the first paleosol layer was warm and humid,the distribution depth of gravity water is up to 4.2mat least and the content of water is adequate in the range of 4.2m.The average moisture content of S1 is about 22% during vegetation growing season and in most time every year.Meanwhile,the available water content is about 14% after evaporation,absorption,crown interception and surface runoff loess.When there was sufficient soil moisture and no dried earth layer developed in the Guanzhong Plain,paleosol can provide enough water to satisfy the need of forest to grow.The distribution depth of gravity water during the development of S1 was 2 mthicker than that nowadays and the soil water was acid.The input volume of soil water was higher than output volume during the development of S1,indicating the value of soil moisture balance is positive and atmospheric precipitation during rainy season could supply the underground with much water.This was why there is high content of soil water at that time.The fact that the distribution depth and content of gravity water in Guanzhong Plain and Luochuan ws sufficient in 2003 can demonstrate that the research results of soil water during the development of S1 is reliable.These indexes indicate that,during the most humid and moisture stage of S1 paleosol development,summer atmosphere surpassed the Qingling Mountains to the Guanzhong

关 键 词：S_1古土壤 化学成分迁移 土壤古湿度 有效水含量 水分存在形式 植被发育条件 关中平原 

分 类 号：S152.7[农业科学—土壤学]