Effects of biological soil crusts on the characteristics of hygroscopic and condensate water deposition in alpine sandy lands

Water resource is scarce in alpine sandy areas. Hygroscopic and condensate water is an important abiotic factor in the maintenance of the local ecological environment. In this research,we used micro-lysimeters which has 10 cm in diameter and 3,4,6 cm in height to measure the variations of the hygroscopic and condensate water content in three types of biological soil crusts(moss,algae,and physical crusts) and moving sand. The results indicated that hygroscopic and condensate water generated almost every day except the windy and rainy days; contents of hygroscopic and condensate water at different land cover types were significant different,and the contents of hygroscopic and condensate water in biological soil crusts were higher than that in moving sand which indicating that biological soil crusts are conducive for the formation of hygroscopic and condensate water. There was an increasing trend of hygroscopic and condensate water content with the development of soil crusts: sand < physical crusts < algae crusts < moss crusts. Hygroscopic and condensate water content occurred from 7: 00 pm to 7: 00 am in the next day. After sunrise,hygroscopic and condensate water content decreasedrapidly within 5 hours. The fastest rate of decrease was found in moss crusts and sand. More than 90% of hygroscopic and condensate water presented in the top of soil within 5 cm which could be used as representative soil depth for further study of hygroscopic and condensate water for low variable coefficient; the contents of hygroscopic and condensate water was negatively correlated with atmospheric temperature and positively correlated with humidity; the hygroscopic and condensate water content was mainly affected by the factors such as sampling depth,surface type,atmospheric temperature,and humidity.