Chin J Plant Ecol ›› 2005, Vol. 29 ›› Issue (5): 747-752.DOI: 10.17521/cjpe.2005.0099

• Research Articles • Previous Articles     Next Articles

EFFECTS OF GRAZING ON THE SOIL SEED BANK OF A STIPA KRYLOVII STEPPE COMMUNITY

ZHAN Xue-Ming1,2, LI Ling-Hao1,*(), LI Xin1, CHENG Wei-Xin1   

  1. 1 Laboratory of Quantitative Vegetation Ecology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
    2 Graduate School of Chinese Academy of Sciences, Beijing 100039, China
  • Received:2004-08-31 Accepted:2004-10-19 Online:2005-08-31 Published:2005-08-30
  • Contact: LI Ling-Hao
  • About author:* E-mail: llinghao@ibeas.ac.cn.

Abstract:

We studied the soil seed bank of a Stipa krylovii steppe community at two sites with different land-use histories: an enclosed pasture, which has been fenced since 2001, and a grazed pasture, which has been continuously grazed for more than 20 years. The experiment was carried out in Duolun County of Xilingol League, Inner Mongolia.
Sixteen 12 cm diameter soil cores were collected to a depth of 5 cm at each site on March 30 and 31, 2004. The soil seed bank was estimated by monitoring seedling emergence, a convenient way to compare soils under similar conditions. Vegetation composition was assessed at each site on May and August 2004 by recording the species presented in sixteen 0.5 m×0.5 m quadrats that were distributed randomly alongside the seed bank sampling points.
A total of 1 593 seedlings belonging to 19 species germinated from 32 soil samples. The total seed bank flora at the two sites included 6 grass species and 13 forbs, 18 of which were perennials and 1 annual, 10 monocotyledons and 9 dicotyledons. In the fenced pasture, there were 16 perennials, 6 grasses and 9 monocotyledons from a total of 16 species in the seed bank, whereas 12 perennials, 4 grasses and 5 monocotyledons from a total of 13 species were found in the seed bank of the grazed pasture. The average number of viable seeds per square meter was significantly higher at the fenced site A ((5 139±1 848) seeds·m-2) than that at the grazed site B ((3 664±1 087) seeds·m-2). Sorensen's similarity index was 0.711 1 for the fenced site and 0.611 1 for the grazed site. In total, only fifteen species were found in the established vegetation at both sites. As many as 81.0 % of the seeds recorded belonged to only five species (Artemisia frigida, S. krylovii, Potentilla acaulis, Cleistogenes squarrosa, and Allium bidentatum). Another 5 species accounted for 16.2% of the seeds recorded and the other 9 species accounted for only 2.8% of the total.
Our results showed that the scarcity of seeds of some important steppe species combined with the unbalanced distribution of seeds among species may inhibit the restoration process of the S. krylovii steppe. Therefore, reseeding and other management steps should be used to speed up the restoration process of the degraded S. krylovii steppe.

Key words: Agro-pastoral ecotone, Degraded pasture, Restoration, Similarity