内蒙古锡林郭勒克氏针茅退化草原土壤种子库特征

Soil seed banks of Stipa krylovii degraded steppe in the Xilin River Basin

以内蒙古锡林郭勒地区克氏针茅(Stipa krylovii)草原不同退化等级群落为对象,研究克氏针茅退化草原可萌发土壤种子库特征。结果表明,随着草原退化程度的增加,不论是土壤总种子库还是持久土壤种子库,组成和密度均明显下降,重度和极度退化草原土壤总种子库密度下降至仅为轻度退化草原的46.8%和11.1%。代表土壤总种子库的4月份取样,轻度、中度、重度和极度退化草原各样地0～9cm土壤种子库密度分别为2800、1278、1311和311粒·m-2;代表持久土壤种子库的6月底取样,4个样地土壤种子库密度分别为1667、967、334和167粒·m-2。多数植物土壤种子库主要分布在0～6cm土层,各样地种子库密度随土壤深度的增加而减少,轻度、中度、重度和极度退化草原4月份0～6cm土层种子库分别占总种子库(0～9cm)的98.4、96.5、95.8和85.7%。不同退化等级草原地上植被与土壤种子库的Sorensen相似性指数介于0.24～0.48。

The soil seed bank is important for vegetation regeneration and natural succession, and it may change as a result of over-grazing. In August 2004, we investigated the community of four sites with different degraded ranks of S. krylovii steppe in the Xilin River Basin, Inner Mongolia. The species present in the vegetation was assessed using five 1 m ×1 m quadrats distributed randomly in each area. In spring 2005, in the same sites, fifteen soil cores （15 cm × 15 cm × 3 cm） were collected from three depth layers （0-3 cm, 3 -6 cm and 6 -9 cm） for each degraded ranks. The composition and density of the soil germinable seed bank was evaluated by monitoring seedling emergence. The similarity of soil seed bank and the standing vegetation was assessed using the Sorensen index. The results indicated that the composition and density of both total soil seed bank and persistent soil seed bank all decreased with the increase of degradation degree, the soil seed density of heavily degraded and extremely degraded steppe dropped to only 46.8 % and 11.1% of slightly degraded steppe. The total soil seed banks （0 -9 cm depth） of slightly degraded, moderately degraded, heavily degraded and extremely degraded steppe in April 2005 had 2800, 1278,1311 and 311 seeds·m^-2 respectively. In June results were lower but showed the same pattern （i. e. 1667,967,334 and 167 seeds·m^-2）. Most soil seeds were found in the top 0 --6 cm, and there was a decrease with depth. The soil seed density （0 -- 6 cm depth） of slightly degraded, moderately degraded, heavily degraded and extremely degraded steppe in April was 98.4,96.5,95.8 and 85.7% of the soil seed density （0--9 cm depth）. Sorensen similarity index of seed bank composition and standing vegetation, was 0.24 -- 0.48.