Responses of alpine meadow seed bank and vegetation to nine consecutive years of soil fertilization

Decline in aboveground species diversity in response to nutrient enrichment has been demonstrated by many studies. However, information on the soil seed bank also is important for restoration of species-rich vegetation, but this subject has received little attention. The aim of this study was to investigate the relationship between the aboveground vegetation and the soil seed bank of an alpine meadow along a fertilization gradient that can germinate in spring. We determined species richness, density, life form and functional groups in the soil seed bank and in the aboveground vegetation along an N-P fertilization gradient from 0 to Fer120 (120 g/m2; i.e. 25.4 g N and 28.2 P m2/yr). Non-metric multidimensional scaling was used to test the similarity between soil seed bank and aboveground vegetation. Species richness of both soil seed bank and vegetation declined in response to 9 years of fertilization, but rate of decline in the seed bank was slower than that in the vegetation. Seed density did not differ along the fertilization gradient except for Fer30, which had the highest seed density. Plant density in the vegetation declined along the fertilization gradient. Proportion of annuals increased both in the vegetation and the soil seed bank along a fertilization gradient. Percentage of different functional groups in the soil seed bank changed but less than that in the vegetation. The similarity between soil seed bank and vegetation increased from Fer0 to Fer90 and then decreased in Fer120. Fertilization influenced species composition of the soil seed bank, but the effect was smaller than that on the aboveground vegetation. The seed bank present in spring provides high species richness and high seed densities for restoration, but restoration to the non-fertilized state would be difficult due to the shift to a higher proportion of annuals and to a low proportion of sedges along the fertilization gradient.