In this study, the effect of biocrusts on daily variations of evaporation in soils of an arid rangeland was investigated during 142 days. Temporal and spatial variations of soil water and solute content were analyzed in three times of 17, 50 and 103 days, and four depths of 10, 20, 30 cm and 40 cm in six columns (20 cm diameter × 50 cm height) containing biocrusts (43 cm saline soil + 5 cm biocrusts) and four columns filled with bare soil (48 cm saline soil) respectively. Temporal variation of evaporation rate was supposed as a 3-stages process. Results showed that stage 1 and stage 2 are not distinguishable. We further found that, compared to bare soil, the biocrusts retarded water evaporation from soil surface (24 vs. 30 mm and 34 vs. 44 mm after 17 and 50 days respectively), and reduced solute accumulation in top soil, especially in the stage 2 of evaporation process (5 vs. 8 dS/m and 13 vs. 20 dS/m after 17 and 50 days respectively). The effect of biocrusts on the evaporation rate at the stage 3 of evaporation was not significant (9 vs. 9 mm after 103 days). Reduction of evaporation by biocrusts resulted in less soil salinity within entire soil profile. The effects of biocrusts on evaporation reduction are attributed to i) the biocrusts create mats on the soil surface, and swelling of mats blocks the soil pores in wet condition, and ii) the large pores of biocrusts disrupt the hydraulic connectivity between topsoil and subsoil, which minimizes the capillary rise. Since major part of water is evaporated during stage 2, and is controlled by water flow within the soil and at the surface, so conservation of the BSCs would be important for preserving hydrological functions advantage such as reducing evaporation and enhancing water retention in the salt affected and dry soils.

在这项研究中，研究了142天生物结皮对干旱牧场土壤每日蒸发量变化的影响。在含有生物结皮的六列（直径为20 cm×高50 cm）中，分别在17、50和103天的三倍以及10、20、30 cm和40 cm的四个深度中分析了土壤水分和溶质含量的时空变化。 （43厘米盐渍土+ 5厘米生物结皮）和四根装满裸露土壤（48厘米盐渍土）的柱子。蒸发速率的时间变化被认为是一个三阶段过程。结果表明阶段1和阶段2不可区分。我们还发现，与裸露的土壤相比，生物结壳可阻止水从土壤表面蒸发（分别在17天和50天后分别为24毫米对30毫米和34毫米对44毫米），并减少了表层土壤中的溶质积累，特别是在蒸发过程的第2阶段（分别在17天和50天后分别为5 vs. 8 dS / m和13 vs. 20 dS / m）。在蒸发的第3阶段，生物结皮对蒸发速率的影响不明显（103天后为9毫米对9毫米）。生物结皮减少蒸发导致整个土壤剖面中的盐分含量降低。生物结皮对减少蒸发的影响归因于：i）生物结皮在土壤表面形成垫层，垫层的膨胀阻塞了潮湿条件下的土壤孔隙，并且ii）生物结壳的大孔破坏了表土与底土之间的水力连通性，从而最大程度地减少了毛细血管的上升。由于水的主要部分在第2阶段蒸发，并且受到土壤内部和地表水流的控制，