松嫩平原西部水文情势变化下土壤盐渍化过程研究

Effect of hydrological process chang on soil salinization in western Songnen plain

土壤盐渍化是松嫩平原存在的主要生态环境问题之一。在年降水量基本保持稳定波动的情况下,松嫩平原西部河流年径流量逐年衰减,自然泡沼和湿地面积日益缩小,区域地下水位普遍呈持续下降趋势。与此同时盐渍化土壤面积却显著增加,特别在低平原地区土壤盐渍化呈扩大和加重态势。土壤原生盐渍化和次生盐渍化过程分析表明:目前松嫩平原发生的土壤次生盐渍化应主要归因于人类的经济活动改变了原来内流区地表的水文过程,极大地减少了地表积水-径流的数量和时间。土壤原生苏打盐渍化是在浅埋深地下水和地面渍涝积水的共同作用下形成的,浅埋深地下水是土壤表层积盐的主要原因,而地面渍涝积水使土壤表层积累的盐分向微地貌的高处迁移,影响了苏打盐渍土在地表的分布格局。在土壤开始发生盐渍化的阶段,浅埋深地下水起了很重要的作用;随着土壤盐渍化程度的加重,地下水盐分向土壤迁移量越来越少;在目前次生盐渍化阶段,地下水对土壤盐渍化作用微弱,甚至可以忽略。

Soil salinization is a main ecological environmental problem in Songnen plain. During past decades,rainfall fluctuated without obvious trends,river runoff declined year by year,natural swamps and wetlands shrank greatly,and regional groundwater level declined gradually. At the same time,the area of salt-affect soils increased significantly and ecological environment deteriorated especially at low plain regions. Analysis of soil primary and secondary salinization processes indicated that the main cause of the ongoing soil salinization was that human activities have changed greatly the hydrological processes over the land surface in past decades,and then decreased significantly the chances and time of flooding and waterlogging in the low plains. The soil salinization was mainly caused by the shallow groundwater and the ponding rainwater. The salt accumulated in the upper soil mainly sourced from the shallow groundwater. The ponding rainwater drove the salt accumulated in the upper soil from the dishes to the rideaus,and formed the current distribution pattern of saline and sodic soils. The shallow groundwater was not a main cause of the ongoing secondary soil salinization,although it played a significant role at early stages in the primary soil salinization.