Soil seed banks and the effects of meadow management on vegetation change in a 10-year meadow field trial.
Enhancement of plant species diversity is often an objective in grassland management for wildlife conservation. Such management regimes may also change the species composition of soil seed banks, which may themselves affect future vegetation change. We compared soil seed banks and vegetation from a long-term meadow management trial and from a series of traditionally managed species-rich meadows in northern England, UK. The management trial used three hay-cut date treatments (14 June, 21 July and 1 September), two fertilizer treatments [no fertilizer or 25 kg nitrogen ha-1 plus 12.5 kg ha-1 phosphate (P2O5) and potash (K2O)] and two seed-addition treatments (no seed, seed of many species sown 1990-92). Soil seed banks were assessed in 1998. Subsequent vegetation development under these treatments, and under an additional farmyard manure treatment, was assessed in 2000. Most seed was in the 0-5-cm soil layer and most of the frequent species germinated in the autumn. Short- and long-term persistent seed banks were most abundant. The species composition of the seed banks and the vegetation in the trial, and in the traditionally managed meadows used as a control, were distinctly different, the meadow trial seed bank being the most uniform. An ordination of simulated plant communities based on the UK National Vegetation Classification provided a wider framework for comparing vegetation and seed banks with the species composition of British meadow communities, some of which are also found in Europe. The soil seed banks throughout the meadow trial plots and the control fields were very similar in species composition to that of the vegetation in agriculturally improved meadows. However, there were many more species in the soil seed bank of the traditionally managed control meadows. In 2000, only the seed-addition treatment increased the species richness of the vegetation. Farmyard manure and mineral fertilizer had similar effects, increasing the cover of Poa trivialis and Rumex acetosa and decreasing the cover of Rhinanthus minor and Anthoxanthum odoratum. It was concluded that the development of the soil seed bank probably lags behind increases in vegetation diversity initiated by seed sowing. This emphasizes the need to introduce additional species as seed when increased diversity is a target for the restoration management of previously intensively managed grasslands.