草地沙化过程地上植被与土壤种子库变化特征

研究了草地沙漠化过程地上植被与土壤种子库的变化特征。获如下结论：(1)草地沙漠化过程地上植被与土壤种子库物种多样性的衰减模式不同，土壤种子库植物种数从潜在沙漠化阶段(固定沙地)到中度沙漠化阶段(半流动沙地)变化很小，而从中度沙漠化到严重沙漠化阶段(流动沙地)衰减速度明显加快；地上植被种数随着沙漠化程度增加而下降，其中从中度沙漠化到严重沙漠化发展阶段衰减幅度最大。(2)地上植被与土壤种子库密度随着沙漠化程度增加而下降，但下降速率因沙漠化发展阶段不同而异，从固定到半固定沙地是地上植被与土壤种子库密度下降最快的时期。(3)地上植被与土壤种子库共有种数随着沙漠化程度的增加而减少，从而导致了地上与土壤种子库群落组成的相异性增大。(4)4种退化沙地土壤种子库组成的相似性要高于地上植被，表明在沙漠化过程中土壤种子库群落组成的稳定性要高于地上植被。(5)地上植被密度与土壤种子库密度存在显著相关性，其关系可用二次曲线来描述。

Characteristics of soil seed bank and standing vegetation change in sandy grasslands along a desertification gradient

In sandy grasslands of the Horqin desert in Inner Mongolia of China, vegetation degradation usually occurs under improper management regimes in fragile environmental conditions. Over the last several decades, most sandy grasslands in this region have become shifting, semi shifting and semi fixed sandy lands corresponding to severe, moderate and light desertification. However, little is known about the effects of degradation level on the structure and performance of soil seed banks and standing vegetation an...