黄土丘陵区生物土壤结皮层水稳性

采用改进的土壤水稳性团聚体数量测定方法，研究了黄土丘陵区不同组成和生物量的生物结皮层水稳定性.结果表明：生物结皮层的水稳定性与其生物组成有关，苔藓结皮的水稳定性显著高于藻结皮，震荡390次后，苔藓结皮的厚度和质量损失率仅分别是藻结皮损失率的47.3%和40.1%；生物结皮层水稳定性与生物结皮的生物组成有关，60%以上苔藓覆盖度的生物结皮的稳定性最高，质量和厚度损失率分别是藻结皮（无苔藓覆盖）损失率的28.6%和22.7%；生物结皮层水平方向结构水稳定性显著大于垂直方向，震荡390次后，苔藓结皮的面积损失率仅为厚度损失率的6.4%.试验分析证实，生物结皮层是一种水平方向稳定性极强的层状结构体，这一结构特性增强了其抗风蚀和水蚀的能力.

Water stability of biological soil crusts in hilly regions of Loess Plateau, Northwest China

By using an improved wet sieving method, this paper studied the water stability of biological soil crusts with different biological components and biomass in the hilly regions of Loess Plateau. The water stability of the biological soil crusts was related to the crusts' biological components. Moss-dominated crust had significantly higher water stability than cyanobacteria-dominated crust. After 390 shakings, the thickness- and mass losses of moss-dominated crust were only 47.3% and 40.1% of those of cyanobacteria-dominated crust, respectively. Moss-dominated crust had the highest water stability when the moss coverage was up to 60%, and the thickness- and mass losses were 22.7% and 28.6% of those of cyanobacteria-dominated crust (no moss coverage), respectively. The horizontal stability of the biological soil crusts was significantly higher than the vertical stability. After 390 shakings, the area loss of moss-dominated crust was only 6.4% of thickness loss. The biological soil crusts had a layer structure with strong stability in horizontal direction, which increased the crusts' resistance against wind- and water erosion.