Secondary succession in sandy old-fields: a promising example of spontaneous grassland recovery

Question Based on the spontaneous vegetation development of old-fields in the Nyirseg and Kiskunsag sand regions (Hungary), we aimed to answer the following questions using the chronosequence method: (1) how do the proportions of different functional groups change during succession; (2) which target species establish successfully in the old-fields during the course of succession; and (3) how successful is spontaneous succession in the recovery of target grasslands? Location Two sand regions of the Great Hungarian Plain: (1) the Nyirseg sand region (East Hungary, acidic sand, moderately continental climate) and the Kiskunsag (Central Hungary, calcareous sand, continental climate). Methods Altogether 24 old-fields were classified into young (<10-yr-old), middle-aged (10-20-yr-old) and late-succession (20-40-yr-old) old-fields; four fields in each age category. For baseline vegetation reference, three open and three closed sand grassland stands in both regions were sampled in the vicinity of the old-fields. The percentage cover of vascular plants was recorded in five 2x2-m plots in each field, in early May and late June 2012. We used life forms, clonal spreading traits and Ellenberg indicator values for nutrients in the analysis. Species of Festuco-Brometea class were considered as target species. Results The cover of hemicryptophytes and geophytes increased, the cover of short-lived species decreased with time. Cover of species without clonal spreading ability decreased, while cover of species with clonal spreading ability increased with increasing field age. The cover of invasive species decreased with increasing field age. The majority of target species had established already in the young and middle-aged old-fields, although their cover was significantly higher in the two older age groups. Conclusion Spontaneous succession can be a vital option in recovery of sand grassland vegetation in Central Europe; the majority of the species pool of sandy grasslands can be recovered in the first 10-20yrs. However, the success of grassland recovery can be strongly influenced by the surrounding species pool and can be slow if seed dispersal is limited. Spontaneous succession is most promising when the target species of grasslands immigrate at the very beginning of the succession, within the first few years.