Vegetation changes in extremely rich fens in Latvia

Abstract

Recent changes in fen vegetation have been studied in many countries but just a few studies have been carried out in eastern Europe. I re-surveyed four extremely rich fens in Natura 2000 areas in Latvia in 2020 where 23 sample plots were established in 2003 in Schoenus ferrugineus dominated plant communities belonging to Caricion davallianae. Cover of five species and three parameters known to be positive or negative indicators for fen conservation status was estimated to reduce the time and expenses of the study in 2003. The same species and parameters were studied in 2020. The expansion of Molinia caerulea was observed in all sites. In sites hosting Myrica gale, its cover remarkably increased. Concurrently, the cover of target species S. ferrugineus increased in two sites but decreased in one site. In another site, its cover decreased close to the fen margin but increased in the fen expanse. To conclude, succession leads to the dominance of expansive species in all sites. The increase of S. ferrugineus cover in two sites cannot be seen as a positive trend either as the area of vegetation-free patches decreases. Consequently, the habitat niches for fen specialist species that are less competitive, e.g. Primula farinosa, Pinguicula vulgaris, decrease. I assume that the vegetation changes were caused by the combined long-term effects of drainage and abandonment.