Abstract:

The species composition, plant life form of aboveground vegetation and the features of soil seed bank such as species diversity and seed numbers under different grazing intensities were surveyed in the Bangjietang Research Station of Tibet. The relationship between aboveground vegetation and soil seed bank as well as the role of seed banks in the construction of aboveground vegetation communities were discussed in order to provide a theoretical basis for alpine meadow management, especially the restoration and reconstruction of degraded ecosystems in the alpine regions. The results showed that the Shannon-Wiener diversity indexes and species richness indexes of soil seed banks were not significantly different between fencing and moderate grazing plots, whereas the Shannon-Wiener diversity and species richness indexes of soil seed banks in heavy grazing plots were significantly lower than those in moderate grazing plots. The seed density in heavy grazing plots was up to 4952.7 seeds·m^-2 and was significantly higher than that in moderate grazing plots. The soil seed densities of all tested plots were ordered as follow: heavy grazing plot >fenced plot >moderate grazing plot. There was no similarity between aboveground vegetation and soil seed bank in both moderate grazing plot and fenced plot. The Sorensen indexes of fenced and moderate grazing plots were 0.48 and 0.44, respectively. In the heavy grazing plots, Kobresia species were degraded severely. Forbs were dominant species in both aboveground vegetation community and soil seed bank. Therefore, there was relatively high similarity between aboveground vegetation and soil seed bank. These results suggested that the fence was effective way to protect degraded ecosystems in the alpine, while it is beneficial to use local excellent perennial grass seed to reseed for the restoration of the degraded alpine meadow. The seeds of soil seed bank in all tested plots were mainly concentrated in 0~5 cm soil layer and the amount of seed decreased with the increase of soil depth.

Key words: Alpine meadow in Tibet, Soil seed bank, Grazing intensity, Species diversity, Plant life form

摘要：

通过研究不同放牧强度下地上植被群落的物种组成、植物生活型、土壤种子库物种种类和种子数量等特征，探讨了地上植被与土壤种子库之间的关系及种子库在地上植被群落构建中的作用，拟为高寒草甸的管理，特别是高寒地区退化生态系统的恢复与重建提供参考。结果表明：土壤种子库物种多样性指数和丰富度指数在围栏样地和中牧样地之间差异不显著。重牧样地土壤种子库物种多样性指数和丰富度指数显著低于中牧样地（P<0.05）；围栏样地、重牧样地、中牧样地土壤种子库密度表现为重牧 >围栏 >中牧，其中重牧样地土壤种子库密度显著高于中牧样地（P<0.05），达4952.7粒·m^-2；中牧样地和围栏样地的种子库和地上植被之间相似性较低，二者的地上植被与土壤种子库Sorensen相似性指数分别为0.48和0.44。重牧样地上嵩草属（Kobresia）植物严重退化，地上植被群落和土壤种子库均以杂类草物种占优势，地上植被与土壤种子库表现出较高的相似性。因此，对于有退化趋势的嵩草草甸，适当的围栏并考虑利用本地多年生优良牧草种子进行补播将是有利的；嵩草高寒草甸土壤种子库种子主要集中在0~5cm，且各样地中种子数量均随着土壤深度的增加而减少。

关键词: 西藏高寒草甸, 土壤种子库, 放牧强度, 物种多样性, 植物生活型