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

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 (P0.05), 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 (P0.01), significantly and negatively correlated with air temperature (P0.01). And, a negative correlation was found between condensation water amount and wind speed (P0.05). Our study can provide scientific supports for evaluation of potential water resources and management of ecosystem in the Mu Us Desert of northern China.