Forming Process Of Soil Condensation Water And Its Response To Environmental Factors In The Mu Us Desert

Water is the main factor restricting plants growth in 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 regions. To clarify the formation of soil condensation water and its response to environmental factors in the Mu Us Desert, we employed micro-lysimeters and used weighing method to study it in the Mu Us Desert in northern China from May to October,2014 and in August, 2015. The results were as follows:(1) Soil condensation water was mainly distributed in the surface layer (0-5 cm) of soil. Formation of soil condensation water included water absorption and condensation, along with water flow from underground soil to surface. It began immediately after sunset, and stemmed from the water in air and underground soil pore.(2) The relationships between soil condensation water and meteorological factors were different in different time scales. Air relative humidity was the key factor to effect on formation of condensation water; the relationship between air temperature and condensation water amount was affected by water vapor condition; the influence of wind speed on soil condensation water was complex:slight wind promoted condensation, while strong wind inhibited it.(3) Seasonal distribution of soil condensation water was different. It had the largest amount in September, while it had the least one in May. The total amount of soil condensation water in a month was significantly and positively correlated with rainfall. Rainfall frequency could affect the amount of condensation water. Rainfall could modify the proportion of two sources of soil condensation water, more soil condensation water came from the water in air when the soil was dry.(4) Shrubs reduced the quantity of soil condensation water. The end time of condensation water in the Artemisia ordosica and Salixpsammophila plots was later than in the sand plot, from which microorganisms in the shrubbery benefitted. Biological crusts might enlarge soil condensation water amount but shorten its duration time; they could promote evaporation during the day. The influence of biological crusts enhanced significantly with its development stages. The amount of soil condensation water was different at different positions of dunes:it had the largest amount at the land between dunes, while it had the least one at the top of dunes.We studied forming process of soil condensation and its response to meteorological factors, brushs, biological crusts and terrain in a desert ecosystem, the results may provide a scientific support for evaluation of potential water resources and the management of ecosystem in the Mu Us Desert in northern China.