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We examined the relationship between the composition and structure of vegetation and hydrology and microtopography within the Paraspõllu calcareous-rich fen (North Estonia). Species composition, depth to groundwater level (+ 6 to-40 cm), pH (6.1-7.1), and electrical conductivity (220-840 µS cm-1) were recorded in 23 relevés of 1 m 2 along transects over the site. The species composition and coverage of vascular plants depended on the extent of water level fluctuations and water conductivity, those of moss species additionally also on microtopography. A total of 44 bryophyte and 57 vascular plant species were identified, including 14 protected and rare species. Nonmetric multidimensional scaling and the Monte Carlo test were used to describe compositional variation and identify significant habitat variables separately for vascular plant and bryophyte species. The relationship between the species composition of field and surface layers was nonsignificant. Three of the five assemblages distinguished by two-way cluster analysis, Carex panicea-Schoenus ferrugineus-Drepanocladus cossonii, Phragmites australis-Calliergonella cuspidata, and Molinia caerulea-Carex davalliana, represent the calcareous tufa-forming fen type. The other two are distributed on the moderately drained part of the fen. The number and coverage of rich fen species decreased sharply as the coverage of M. caerulea exceeded the 30% level and seasonal fluctuation of water level was over 25 cm.

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The number and the area of former milled peatlands under restoration have increased rapidly in the Northern Hemisphere in recent decades with the primary aim of promoting peat accumulation. However, the application of similar restoration techniques across different sites does not always lead to desired results, and some site-specific modifications may be needed. This study aimed to evaluate the response of aboveground plant biomass on three experimental sites in northern Estonia to different restoration techniques in degraded peatlands. The sites were restored using the moss layer transfer technique, which was modified with different plant spreading rates and species composition of spread material, fertilization, and creating variations in microtopography. The strongest effect of manipulations was found for bryophyte biomass responses to treatments. The creation of a microtopographic relief during the site preparation phase favored the development of Sphagnum biomass in depressions rather than in positive microforms. The species composition of the spreading material had some effect on bryophyte biomass: Sphagnum biomass was higher where hummock species had been spread. We did not find any statistical difference in the ratio of Sphagnum reintroduction tested ranging from 1:10 to 1:15.

Peatlands are globally important ecosystems for their habitats, carbon sink and freshwater reservoir functions. Estonia is among the most peatland-rich countries worldwide with ca 20% (9,150 km 2 ) of its land area covered with peat soils. Majority of these peatlands, however, are altered by the drainage for the agriculture, forestry and peat extraction that has led to a degradation of peatland ecosystems, and declined their functioning. The rapid loss of peatland habitats, subsidence of peat soils and carbon emissions after water level drawdown have highlighted the need for the ecological restoration of drained peatlands. Although the first restoration attempts in the early 2000s in Estonia covered only minor areas, the current increase of restoration projects in quantity and quality has been promising, and the aim to restore 10,000 ha of degraded sites in Estonia for 2020 is likely to be implemented.

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The spatio-temporal development pattern of a mire system and major factors affecting this process were studied. The Soomaa mire system (25 100 ha) in south-western Estonia is one of the largest and best preserved mire systems in Estonia. Using the bulk densities of peat layers and radiocarbon dates average accumulation rates and increments of different peat types were calculated. On the basis of the obtained and already existing stratigraphical data the probable development of the mire system was reconstructed. Paludification of the Soomaa region started about 10 000 BP and ombrotrophication 7000-6000 BP. The expansion rate of the mire system was rather stable during the whole Holocene and no distinct relationship between the climate and the expansion of mires was detected. The results suggest that the expansion of mires was mostly an autogenous process, while ombrotrophication might have been favoured also by climate changes.The spatial dynamics of paludification was mainly determined by local factorstopographical and hydrological characteristics of the area.