The species composition of the seed bank and aboveground vegetation of an old field was compared to a reference grassland stand. The relative importance of dispersal and recruitment as limiting factors was analysed, and measures for appropriate restoration are proposed. Grassland species were able to re-establish in the old field soon after abandonment of cultivation, with Stipa borysthenica as the dominant species. Five years after abandonment of cultivation, the seed bank was still dominated by weedy annuals while grassland species made a relatively high contribution to the seed bank in the reference site. The results do not support recruitment to be the limiting factor in recently abandoned fields, because grassland species that occurred in the seed bank were also present in the vegetation. A rapid regeneration of the matrix species is predicted due to their good dispersal capacity and the vicinity of the open sand grassland. However, the introduction of subordinate species and the control of invasive plants might require human intervention.
Authors:A. Csecserits, R. Szabó, M. Halassy, and T. Rédei
We studied the vegetation of 54 sandy old-fields abandoned at different times. We first surveyed the vegetation in 1998 and developed predictions about the spontaneous succession using the chronosequence approach. Afterwards, we repeated the survey in 2000, 2001, 2002 and 2003, and based on this monitoring we tested the predictions of the chronosequence study. For both approaches, we analysed the changes in functional group composition during succession. According to the chronosequence study, the most important changes occurred in the youngest old-fields, abandoned 1–4 years ago: the species number and abundance of annuals, disturbance-requiring and anthropogenic species decreased, and those of perennials, grassland generalists, and species with low disturbance-tolerance increased. No changes were predicted for the older fields. The monitoring confirmed the predictions for the youngest old-fields. However, during the 5 years of monitoring several functional groups changed in their species number or abundance even on the older abandoned fields. Both of the methods showed that secondary succession on sandy old-fields is relatively fast. The chronosequence study provided a more static view of the processes, while the multi-year monitoring revealed that there were considerable inter-annual changes as well. With the yearly monitoring we can detect the effect of additional factors, such as land use changes (e.g., changes in grazing intensity) and yearly climate fluctuations on the direction and rate of secondary succession.