毛乌素沙地不同下垫面地表凝结水形成过程

Forming process of soil condensation water on different types of underlying surface in Mu Us Desert,northern China

水分是制约干旱半干旱地区植物生长的主要因子。土壤凝结水数量虽小,但作为一种持续稳定的水源,对于维持干旱半干旱地区的生态平衡至关重要。为了深入了解下垫面差异对地表凝结水形成过程的影响,于2014年7—8月采用称质量法,在毛乌素沙地使用微渗仪对裸沙地、油蒿林地、沙柳林地的地表凝结水形成进行观测,并对相关气象因子和土壤温度进行同步监测。结果表明:1)地表凝结水形成在日落后即刻开始,而在日出约1 h后停止,3种下垫面地表凝结水形成规律近似;油蒿和沙柳林地的地表凝结水结束时间晚于裸沙地,有助于延长林地隐花植物和微生物对凝结水的吸收时间。2)在观测期(17 d),裸沙地、油蒿林地、沙柳林地的地表凝结水总量依次为3.332、2.382、1.817 mm,裸沙地日均凝结水量显著大于油蒿和沙柳林地(P<0.05),表明灌丛覆盖会改变近地面性质和林内小气候,导致地表凝结水量减少。3)地表凝结水量与空气相对湿度呈极显著正相关关系(P<0.01),与气温呈极显著负相关关系(P<0.01),与风速呈显著负相关关系(P<0.05)。以上研究结果可为毛乌素沙地潜在水资源评估和生态系统管理提供依据。

Water is the main factor restricting plant growth in arid and semi-arid regions. Although the amount is very small,soil condensation water,as a sustained and steady water source,is very important to the ecological balance in arid and semi-arid regions. To clarify the formation of soil condensation water on different underlying surfaces,we employed micro-lysimeters and weighing method to study the formation process of soil condensation water and factors affecting it in three plots（ sand plot,Artemisia ordosica plot and Salix psammophilia plot） in the Mu Us Desert in northern China from July to August,2014.Meteorological factors and soil temperature were supervised at the same time. The results were as follows：1） formation of soil condensation water began immediately after sunset,and ended about one hour after sunrise. Nocturnal regularity of formation of soil condensation water was similar in the three plots. The ending time of condensation water in the A. ordosica and S. psammophilia plots was later than in the sand plot,from which microorganisms in the shrubbery benefitted. 2） During the 17-days observation,the total amounts of condensation water in the sand,A. ordosica and S. psammophilia plots were 3. 332,2. 382 and 1. 817 mm,respectively. Daily average amounts of condensation water in the A. ordosica and S. psammophilia plots were less than in the sand plot（ P〈0. 05）,presumably due to the change of underlying surface properties and microclimate caused by shrub cover. 3） Condensation water amount was significantly and positively correlated with relative humidity（ P〈0. 01）,significantly and negativelycorrelated with air temperature（ P〈0. 01）. And,a negative correlation was found between condensation water amount and wind speed（ P〈0. 05）. Our study can provide scientific supports for evaluation of potential water resources and management of ecosystem in the Mu Us Desert of northern China.