The development of soil crust on sandy land may affect the surface hydrological process.This paper investigates the process of evaporation and dew deposition influenced by different soil surface types which were dominated by sand,primitive biotic crust,and advanced biotic crust,respectively,in the south fringe of Mu Us sandy land in Northwest China from July to September of 2006.The experimental results indicate that the advanced biotic crust could increase evaporation and dew deposition compared to the primitive biotic crust and bare sand although the differences between them were not significant.The average evaporation from advanced biotic crust,primitive biotic crust and sand was 6.8,6.6,and 6.5 mm/d,respectively,and water content is around 16.2%in the condition of initially identical soil.The average dew amount on advanced biotic crust was 0.116 mm/d with extreme 0.05 and 0.24 mm/d.The average values on primitive biotic crust and sand were 0.105 and 0.101 mm/d,respectively,with extreme 0.04 and 0.21 mm/d for both treatments.Also,the dew deposition on advanced biotic crust seemed stable and might rest for a longer time than that on primitive biotic crust and sand.The results suggest that the advanced biotic crust possibly facilitates evaporation and dew deposition.Therefore,the development of biotic crust may potentially enhance the hydrological circulation in the upper sand layer in sandy land.
Little work has been done on stemflow for desert shrubs in China. This study measured stemflow in two shrubs of Salix psammophila C. Wang et Chang Y. Yang and Artemisia sphaerocephala Krasch in Mu Us sandy land and established a relationship between stemflow and canopy characteristics, rainfall amount and intensity. During the experimental period, the amount of stemflow for S. psammophila and A. sphaerocephala accounted for 7.6% and 2.7% of the gross rainfall respectively. Statistical analysis showed that there was a significant positive linear correlation between rainfall and stemflow for the two shrubs; while the relationship between stemflow percentage and rainfall suggested that there existed a rainfall depth threshold of 3―5 mm for S. psammophila and 5―7 mm for A. sphaerocephala. Stemflow percentage positively increased with rainfall depth increasing before the rainfall depth threshold values had been reached but showed stability after the threshold. A stepwise regression analysis suggested that the shrubs with more branches, larger crown volume and smaller branch angle inclination tended to collect more volumes of stemflow. Moreover, stemflow amount and percentage increased with the maximum rain intensity increasing in 10 minutes (I10) and the stemflow percentage tended to increase quickly with I10 when it was less than 3.0 mm h-1 for S. psammophila and 2.0 mm h-1 for A. sphaero- cephala, and then showed stable trend with increasing of I10.
YANG ZhiPengLI XiaoYanLIU LianYouWU JianJunHASI EerdunSUN YongLiang
