Abstract:

The regeneration of plant community after disturbance depends on the availability of propagules. In grasslands, soil bank is the primary source of propagules, although propagule arrival from neighbouring areas may be important as well. There is evidence that in several grasslands there is a low similarity in floristic composition and in the relative abundance of plant species between the standing vegetation and their soil seed banks. The objective of this study was to evaluate the floristic composition, abundance, richness and diversity of the soil seed bank and the standing vegetation and to assess their relationship, in a closed field of the pampean prairie where a secondary succession has developed after 20 years. Thirty-six samples of vegetation and soil were analysed, classified and ordered with multivariate methods. In the standing vegetation, we recorded a total of 13 species, most of them perennials. The dominant species was Sorghum halepense. In the seed bank, we identified 12 species, most of them annuals, and Portulaca oleracea was the most abundant one. The floristic groups of the standing vegetation were more clearly defined than those groups of the soil seed bank. Three species (Sorghum halepense, Carduus acanthoides and Verbena bonariensis) were present in both the seed bank and the standing vegetation, but only for S. halepense showed a positive correlation between both the seed bank and the standing vegetation. The low similarity between the standing vegetation and the soil seed bank shows that, except for Sorghum halepense, the dominant species of the standing vegetation contribute very little to the development of the soil seed bank.