陕北水蚀风蚀交错区小流域苔藓结皮的空间特征及其影响因子

生物结皮是旱区普遍存在的活性地被物，在生态系统中发挥重要的生态功能，研究其发育特征与形成机理是有效管理和利用该资源的基础。退耕还林（草）工程实施以来，黄土高原地区生物结皮大面积发育，但相比荒漠地区，相关的研究工作还较薄弱。生物结皮的发育具有过程的复杂性和空间的分异性，诸多荒漠地区的研究结果不能直接外推至黄土高原地区。鉴于此，论文选择黄土高原典型小流域，通过全面调查和测算分析，应用GIS 软件，探讨了生物结皮的空间特征及其影响因子。结果表明：①流域内藓类共有2 科8 属13 种，狭网真藓、真藓、尖叶对齿藓分布最广；②苔藓结皮占绝对优势，面积为4.18 km²，占流域面积的60.7%，主要分布在干扰少、侵蚀弱、水分好的梁峁坡或梁峁顶上；③土壤、植被、坡向均对苔藓结皮的发育有显著影响。同黄土地相比，沙地苔藓结皮的覆盖度高、呈连片分布。乔、灌植被下的生物结皮发育优于草本群落，植被盖度对苔藓结皮产生先促进后抑制的作用（拐点约在覆盖度30%处）。总体上，阴坡生物结皮的覆盖度、厚度均高于阳坡。

Spatial Characteristics of Moss-Dominated Soil Crust and Its Impact Factors in Small Watershed in Wind-Water Erosion Crisscross Region,Northern Shaanxi Province,China

Biological soil crusts (BSCs) are a widespread ground living cover in arid and semi-arid areas, which serve as an important ecological function in ecosystems of arid areas. To study its development characteristics and formation mechanism is the basis of effective management and utilization of these resources. Since the implementation of Grain for Green Project, the ecosystem of the Loess Plateau recovered extensively, and BSCs widely developed. However, the related researches are still deficient compared to those in the desert area. Due to the complexity of BSCs' development process and its spatial differentiation, many results of researches carrying out in desert areas can not be directly extrapolated to the loess area. In view of this, this paper chose a typical small watershed in the Loess Plateau, carried out a comprehensive survey, made lots of calculation and analysis by using GIS software, discussed the distribution characteristics of the BSCs and its influencing factors. The results showed that: 1) a total of 13 species of mosses belonging to eight genera under two families were found in the watershed. Of which Bryum algovicum Sendt., Bryum argenteum Hedw. and Didymodon constrictus (Mitt.) Saito. are most widely distributed. 2) Moss crust had the absolute advantage with an area of 4.18 km², accounting for 60.7% of the watershed area, which are mainly distributed on the hill slope or slope top for less erosion or less disturbance, and better soil water conditions. 3) Soil, vegetation and slope aspect had a significant effect on the development of BSCs. Compared with the loess area, BSCs in sandy area had a high coverage and showed a continuous distribution. The development of BSCs under the tree and shrub vegetation was superior to those under herbaceous communities, and the vegetation coverage promoted first and then inhibited the development of BSCs (inflection point at 30% of the coverage). Overall, the coverage and thickness of the BSCs were greater on shady slope than those on sunny slope.