古尔班通古特沙漠表层土壤凝结水水汽来源特征分析

Source of Soil Condensation Water in the Gurbantunggut Desert

水分条件是决定干旱沙漠区生态环境的关键因素,凝结水是干旱区植物和低等生物的重要水分来源。利用自制蒸渗计在春、夏、秋3个季节对古尔班通古特沙漠苔藓、地衣、藻类及流沙4种地表类型表层原状土壤凝结水形成进行了观测研究。结果表明,在2cm、5cm、10cm、20cm 4种高度原状土中,用纱网封底土壤表层2cm和5cm土壤的凝结水测定结果能够真实的代表古尔班通古特沙漠不同类型地表土壤凝结水形成特征;凝结水主要集中产生在土壤表层2cm范围内;凝结水的水汽来源于空气和土壤且以空气来源为主,春季由于表层土壤含水率较高,来自于土壤的水汽所占的比重较高,地衣0～2cm表层凝结水来源于土壤水汽补充的比例春季为35.5%,夏季和秋季分别降到15.5%和11.3%;秋季55d的观测结果表明,凝结水形成总量随流沙、藻类、地衣和苔藓依次增加,分别为3.46mm、4.07mm、4.89mm和5.15mm,说明在干旱的沙漠地带,凝结水是除降水以外补充表层土壤水分最重要的水分来源。

Water is a key factor for desert ecological environment.Soil condensation water is an important source of moisture for plants and lower organisms.By making use of homemade micro-lysimeter we measured soil condensation water from different soil crusts（cyanobacterial crust,lichen crust and moss crust,and bare sand as check） within surface undisturbed soil columns underlaid with nylon yarn net bed or waterproof plastic film.Soil condensation water is mainly formed in the upper 2 cm soil layer,and originates from two separate sources： the soil and the air,but the latter was more important.The proportion of soil condensation water within surface 2 cm soil layer from the soil source is 35.5% in spring,15.5% in summer,and 11.3% in autumn because the soil water content decreases from spring to autumn.The total condensation water in 55 days in autumn is 3.46 mm from bare sand,4.07 mm from cyanobacterial crust,4.89 mm from lichen crust,and 5.15 mm from moss crust.The results suggest that,besides precipitation,the condensation water is an essential source for replenishing surface soil water in arid and semi-arid areas.