摘要
Based on secular fixed_site data in the artificial sand_fixing vegetation district at the southeast fringe of the Tengger Desert, the formative characteristics of soil microbiotic crusts and its influences on vegetation dynamics were analyzed. Once sand barrier and artificial vegetation have stabilized the surface of the sifting sand, could form aeolian deposition crust and then evolve into algae_dominated crust. Such processes result from the interactions of physical effects of atmospheric dust and silt deposition on sand surface, sinking and raindrop impact, and soil microorganism activities. Under the condition of less than 200 mm precipitation, the presence of microbiotic crust changes the soil hydraulic conductivity, alters the temporal and spatial distribution of the limited precipitation in sand layer and leads to the decline of deep_rooted shrubs. The development of microbiotic crust and subsurface soil affects the plant growth and seed rain distribution, as a result, the diversity of plant species gradually tend to become saturated and finally affects the vegetation stability.
在腾格里沙漠东南缘人工固沙植被区 ,采用已有的数据和长期的定位观测 ,分析了固沙植被区生物结皮的形成特点及其对植被动态的影响。流沙经过沙障固定和种植植物后 ,沙土表层形成风积物结皮 ,再演变成以藻类为优势种的微生物结皮 ,而这一过程是因沙物质得到固定后 ,大气降尘和粉粒在沙表层堆积、下沉 ,再经雨滴的冲击等物理作用和土壤微生物的活动共同作用的结果。在降水不足 2 0 0mm的条件下 ,结皮的形成改变了土壤水分的传导 ,有限的降水在沙土层中的时空分布发生了变化 ,使深根系的灌木逐渐衰退 ,浅根系的植物得到了发育。结皮和亚表层土的发育影响了植物的生长和种子雨的分布 ,使植物种的多样性渐趋于饱和状态 ,并最终影响到植被的稳定性。
基金
TheNationalNaturalScienceFoundationofChina ( 3 9990 490 )
TheFoundationofShapotouOpenExperimentStation
TheChineseAcademyofSc
