Abstract:In desert environments, dew is an important source of moisture for plants, biological soil crusts, invertebrates and small vertebrates. In this paper, measurements were taken to investigate the effects of three different types of biological soil crusts (algae, lichen, moss) and bare sand on dew deposition, dew duration and evaporation pattern in Gurbantunggut Desert. Dew quantities were measured using micro-lysimeters with a diameter of 6 cm and a height of 3.5 cm. The results indicated that the total dew amounts of different soil surface types were significantly different (p < 0.01), it increased with the development of biological soil crusts, in the following order: sand < algae crust < lichen crust < moss crust. It can be concluded that the occurrence of biological soil crusts benefited dew deposition. Average daily dew amounts varied along with different soil surfaces. During the period of this study, for each type of crust studied, the maximum amount of dew was several times greater than the minimum. Moss crust was characterized by having the greatest amount of dew at dawn, whereas bare sand yielded the lowest amount of dew, lichen crust and algae crust exhibited intermediate values. Dew deposition began at 20:00-22:00 and ended at 8:00-9:00 the next morning. A continuous dew deposition even after sunrise was also observed. The time course of dew accumulation and drying on different soil surfaces could be divided into two parts: dew amounts increased gradually before sunrise, and after then dew amounts decreased rapidly with higher temperature. Dew deposition was mainly affected by air temperature near the surface, soil temperature, the air relative humidity and the kind of surface. The data, thus, indicated the important effect of biological soil crusts on dew formation and may assist in evaluating the significant ecological role of dew in the arid and semi-arid environments.