Floristic composition of vegetation and the soil seed bank in different types of dunes of Kerqin steppe

摘要

The floristic composition of the vegetation and the soil seed bank in different types of dunes of Kerqin steppe were compared. The aim of this study was to examine the influence of desertfication on the floristic composition of the vegetation and soil seed bank. An indirect germination method was used to study the seed batik. Thirty species of the vegetation and 25 of the seed bank were identified, 23 species being common to both. Differences between four types of dunes (mobile sand dune, MSD; semifixed sand dune, SSD; fixed sand dune, FSD; interdunal lowland, ILD) in floristic composition of the vegetation and the soil seed bank were examined using nonparametric methods. In the four types of dune, species composition varied significantly except between site MSD and site SSD as well as between site FSD and site ILD in aboveground vegetation. As for soil seed bank, the number of species and seeds differed significantly only between site FSD and site ILD. Species diversity revealed that species numbers increased in the sequence of MSD, SSD, FSD and ILD. The dominant species of aboveground vegetation in site MSD and site SSD were Agriophyllum squarrosum and Setaria viridis, respectively. While in both site FSD and site ILD, the dominant was Eragrostis pilosa. Of total germinated seed, the most abundant species in site MSD were Agriophyllum squarrosum, but the dominant species was Eragrostis pilosa in the other three sites. In each site, more than half of the species recorded in aboveground vegetation were found in the seed bank, even more in the seed bank of site FSD and site ILD. In site FSD and site ILD, high correspondence was observed between the species composition of the aboveground vegetation and of the associated soil seed bank. Spearman's rank correlation coefficients were 0.295, 0.046, 0.704, and 0.612 for site MSD, site SSD, site FSD and site ILD, respectively. These results indicated that desertification development decreased correlation between the seed bank and vegetation in Kerqin Steppe.