Browsing by Subject "häädetkeidas"

Primary peat formation, infilling (terrestrialization) and paludification are the three main kinds of peatland formation processes. A peatland can develop over previously drier mineral soil if water table level rises or previously formed mire grows or expands. In Finland, the expansion of mires has been occasionally fast and in major part of ombrotrophic raised bogs it has occured while the mire has been in the minerotrophic fen stage. However, based on previous studies there have been different speculations whether the paludification still continues. Paludification study site at the edge of peatland and forested mineral soil was established in Häädetkeidas Strict Nature Reserve in year 1931. The study site, with a set of 4 transects, was studied in 1931, 1945, 1957 and 1997. Vegetation analysis on these permanent transects was repeated in 2016 as a part of this thesis. The aim of this study was to describe the variation of vegetation at the edge of the mire and forested mineral soil and study how the vegetation and plant species assemblies have changed between the years 1931–2016. A long-term vegetation study can reveal whether the species have changed from forest-dominated species to peatland-dominated species and does the paludification process still continue. The paludification process was studied by estimating the canopy-cover of ground layer and field layer vegetation and litter cover, measuring peat thickness, the thickness of aerated peat layer and anoxic peat layer and forest cover in four transects, consisting of 180 subplots. Non-metric multidimensional scaling (NMDS) was used to describe the data. Ground and field layer vegetation were examined by comparing the species’ average cover and frequencies. Environmental variables were studied by correlation analysis. Differences in peat thickness and in the coverage of Sphagnum-mosses between the examination years were studied with oneway variance analysis and t-test. In all four transects the coverage of Sphagnum-mosses had increased between the years 1931 and 2016. The coverage of forest mosses had decreased in two out of four transects. Succession related changes in species were observed in both vegetation layers. There was variation in the vegetation development between the transects and they seemed to be in different stages of the succession and paludification processes. In 93 percent of the study plots the thickness of peat layer had increased during the last 19 years. The changes in vegetation between the years 1931 and 2016 as well as the growth of the peat layer suggests that the paludification process still continues.