Understorey Vegetation on Three Ombrotrophic Pine Bogs and the Effects of NPK and PK Fertilization

The understorey vegetation was compared and the short-term effects of fertilization studied on three drained peatland sites, one in eastern Finland, and the other two in southern Norway and Sweden. The original vegetation on all the sites was typical of ombrotrophic pine bogs. There were differences between the sites in species composition and abundance. The first dimension of detrended correspondence analysis was related to the depth of the groundwater table. It is likely that this factor will gradually lose its significance as the drainage improves on the Swedish and Norwegian sites. NPK and PK fertilization had some effects on the abundance and frequency of the plant species. The vigour of the field layer was positively affected on the Norwegian and Swedish sites. Eriophorum vaginatum and Rubus chamemorus most clearly benefitted from fertilization. In the bottom layer, Sphagnum species suffered on all three sites. Pleurozium schreberi on the Finnish site, as well as Aulacomnium palustre on the Norwegian site, increased their coverage after fertilization. Some new field layer species, e. g. Dryopteris spp., and Epilobium spp., became established during the course of the study in Finland and Sweden. Some new moss species, e. g. Plagiothecium in Finland, Mnium sp. in Sweden and Ptilidium sp. in Norway, were also found in the bottom layer, although they occurred only sporadically as new species. There were no clear differences between the effects of the individual fertilization treatments on the field layer, but the total coverage of the bottom layer decreased more after NPK than PK fertilization.