Restoration potential of the persistent soil seed bank in successional calcareous (alvar) grasslands in Estonia

Abstract

Questions: What is the overall restoration potential of the persistent soil seed bank of abandoned alvar grassland sites? To what degree does the share of characteristic alvar grassland species in the soil seed bank change during secondary succession from traditionally managed pasture towards stages overgrown by Corylus avellana and Juniperus communis?Location: Northern Estonia.Methods: The species composition of above-ground vegetation and the persistent soil seed bank were investigated in successional alvar grasslands. Particular attention was given to typical grassland species in the persistent soil seed bank. Soil seed bank density was also recorded. General linear models and non-metric multidimensional scaling were used to assess successional trends and the restoration potential of the soil seed bank.Results: The cessation of traditional management has led to a considerable decline in above-ground plant species richness. The composition of aboveground vegetation in different successional stages was considerably more variable than that of the seed bank. We detected large and species-rich persistent soil seed banks in all our study sites. About 70% of species in the seed banks of overgrown sites could be classified as typical grassland species. The frequency of typical alvar grassland species, such as Arabis hirsuta, Arenaria serpyllifolia, Cerastium fontanum, Helianthemum nummularium, Poa angustifolia, Potentilla crantzii, Sedum acre and Veronica spicata in the seed bank of long-term abandoned (25 and 50 yr) sites was unexpectedly high.Conclusions: Abandoned semi-natural grassland sites in northern Estonia still contain a relatively large grassland community species pool, including a large and effective soil seed bank. The soil seed bank could thus play a more important role in the restoration management of abandoned dry grassland communities than could be concluded from previous studies.

Factors affecting re-vegetation dynamics of experimentally restored extracted peatland in Estonia

“…Propagule banks are considered crucial for re-establishment of pre-disturbance communities (Caners et al 2009;Kalamees et al 2012). Millennia-old peat layers exposed during peat extraction contain no viable propagules (Salonen 1994), and propagules arrived after peat extraction will be removed during stripping of the surface peat layer.…”

Can we rely on the soil seed bank for restoring xeric sandy calcareous grasslands?

“…There is contradictory evidence in the literature concerning the contribution of seed banks to the restoration of dry grasslands. Some authors argue that the soil seed bank can play an important role in the restoration of degraded sites, such as in Estonian calcareous grasslands (Kalamees et al ) or in Chinese sandy grasslands (Miao et al ). Our results showed that dry grassland specialist species already missing from the vegetation communities are no longer present in the soil seed bank.…”

Severe effects of long-term drought on calcareous grassland seed banks

“…Seed banks represent biodiversity reservoirs for grasslands and other ecosystems on a global scale, 31 playing an important role in the maintenance of genetic and species diversity, 32,33 and in the reestablishment of species lost from the above-ground vegetation. 34 Moreover, they reduce the risk of extinction as a consequence of a single environmental event such as drought or flooding. 35 Therefore, seed banks are often thought to buffer the responses of plant communities to climate variation, 36 providing potential resilience to disturbance or environmental shifts, 31 and to decrease extinction vulnerability under climate change.…”