塔里木河下游荒漠化过程土壤种子库特征

Characteristics of Soil Seed Bank along Desertification Gradient in Lower Reaches of Tarim River

沿塔里木河下游荒漠河岸林，选择了荒漠化程度依次加重的5个断面，进行了土壤种子库野外萌发试验。结果表明：①在中度荒漠化区土壤种子库的物种相对丰富（11种），密度较高（892.6粒·m^-2）；随着荒漠化程度的加剧，土壤种子库物种丰富度、总密度以及多样性指数呈现出明显下降的趋势；②与重度荒漠化区和中度荒漠化区相比，极度荒漠化区土壤种子库中的多年生草本和灌木密度占总密度的百分比有所增加，一年生草本百分比明显降低；③不同荒漠化程度对种子库密度的垂直分布影响不大，70％以上的种子集中在土壤表层0-2cm深度。综合来看，随着荒漠化程度的加剧，土壤种子库的恢复潜力有所下降。

Over the past 50 years the desert riparian vegetation in the lower reaches of the Tarim River in western China degraded due to irrational management regimes. Little is known about the effect of vegetation degradation level on the structure and performance of soil seed bank in desert riparian vegetation. A field experiment was established to test this effect. The results showed that the density （892.6 seeds·m^-2） and species number（11 species） of soil seed banks in the moderate-desertification transects are relatively high. With the increase of desertification level the species abundance, density and biodiversity index of soil seed bank decrease. There is no significant effect of desertification intensity on the vertical density distribution of soil seed bank. However, over 70% of seeds were concentrated in the upper oil layer （0-2cm）. Plots at extreme desertification level showed a greater proportion of annual herbs compared to plots at heavy or moderate desertification levels, whereas perennial herbs and shrubs followed the inverse trend. These results indicate that the potential of the natural vegetation to restore naturally decreases with the increase of desertification level.