Question: Can combined sod cutting and liming successfully restore species composition of degraded wet heaths?
Location: The Netherlands.
Methods: The effects of sod cutting with or without liming on plant species composition were studied in two degraded wet heath areas. Seeds and seedlings of Arnica montana were put out in the treated plots to test the suitability of the restored soil conditions. In addition, seed banks of both degraded areas were studied.
Results: Germination, growth and survival of Arnica montana were significantly greater after sod cutting and liming compared to sod cutting alone. At the end of the four-year study period, the number of endangered wet heath species was significantly greater in the sod-cut plots than in the untreated vegetation. Acid-tolerant species were especially positively affected. Additional liming only slightly increased the total number of species over the two-year study period and the number of endangered species did not increase. Viable seeds of most of the endangered species were absent in the seed banks of both areas.
Conclusions: Sod cutting is sufficient for the return of acid-tolerant, endangered wet heath species of early successional stages, because their seeds are still present in the seed bank. In contrast, acid-sensitive species likely depend on combined sod cutting and liming, as they need the weakly buffered soil conditions created by these restoration measures. However, successful restoration of formerly species-rich wet heaths is limited significantly by the absence of seeds of the target species in the seed banks. Therefore, re-introduction of wet heath target species in areas with limited seed availability should be seriously considered.
Abbreviations: HO = Havelte-Oost heathland; LP = Leem-putten nature reserve.