Effect of soil crust on evaporation and dew deposition in Mu Us sandy land,China

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.

The ecological role of dew in assisting seed germination of the annual desert plant species in a desert environment, northwestern China

It is important to understand the effects of dew events on non-mucilaginous seed germination of annual desert plant species during dry seasons, which is critical to maintaining long-term soil seed banks in a harsh desert environment. We hypothesize that dew deposition also assists in the non-mucilaginous seed germination of annual desert species. A common field dew treatment experiment was conducted in the Linze Inland River Basin Research Station to investigate the effects of dew deposition on the seed germination of four annual species, including Agriophyllum squarrosum, Corispermum mongoficum, Bassia dasyphylla and Halogeton arachnoideus. The results showed that the presence of dew significantly increased seed germination percentages and decreased the nonviable seed percentages of B. dasyphylla and H. arachnoideus, whereas there was no such trend for the seeds of C. mongolicum and A. squarrosum. The ecological effects of dew on the seed germination and viability of the annual desert plants were species specific. Although dew wetting is insufficient to cause seed germination, it may help in priming the seeds.