Short-term seed banking enables adaptive, multi-year seeding strategies in grassland restoration

Ex situ seed banks can play a critical role in supporting grassland restoration and mitigating the impacts of climate change by ensuring a continuous supply of native seeds. We investigated the effects of short-term seed storage (fresh, one-, two-, and three-year storage) and seeding year (2011–2014) on the restoration of open sand grassland using accessions from the Pannon Seed Bank in Hungary. Seeds of ten native species were sown in an abandoned sandy field, and vegetation was monitored for up to nine growing seasons. Clear directional development toward the reference grassland became evident from the fifth year onward. Target species reached up to 90% relative cover, primarily due to the sown species, while non-target natives and neophytes declined. Differences among storage treatments were only transient, e.g. higher species richness when using fresh seeds, and by the end of the monitoring period all seed storage durations converged toward the reference community. In contrast, seeding year had a lasting influence: plots sown in years with favorable precipitation (e.g., 2013) showed stronger establishment of target species, while less favorable years (e.g., drought in 2012) constrained recovery. These year-specific effects shaped both the long-term success of target species and invasion dynamics. Restoration outcomes were therefore more strongly influenced by seeding year than by storage duration, underscoring the need for adaptive restoration strategies tailored to year-specific conditions. We recommend multi-year, scheduled seeding as a buffer against adverse weather, supported by the short-term use of seed banks to ensure seed availability under variable climatic conditions.