Factors affecting the re-vegetation of abandoned extracted peatlands in Estonia: a synthesis from field and greenhouse studies

Re-vegetation of extracted peatlands is a slow and sporadic process. The aim of our study was to clarify whether this process is affected by the distance from vegetated areas and propagules arrival or by the conditions for propagules germination and plant growth. Our analysis is based on three extracted peatlands in Estonia, abandoned 26-31 years ago. In all study areas vegetation was analysed on the gradient from a neighbouring vegetated area towards the central part of the peatland. In addition, peat blocks were collected from the marginal and central parts of the peatlands, held in favourable moisture conditions for seed germination in a greenhouse, and half of them were fertilized with a complex fertilizer. Our study showed the species pool to be present everywhere on abandoned extracted peatlands, but the germination was influenced by different factors such as water table, peat chemistry, etc. The species richness on extracted peatlands was higher close to the neighbouring vegetated areas and decreased towards the central part of the peatland, but for the peat blocks held in the greenhouse, the number of species was higher for the blocks collected from the central parts of the peatlands. The proximity of the vegetated area did not increase the number of species developed in the greenhouse whereas higher moisture and temperature conditions initiated the growth of many additional species not found on the extracted peatlands. Our study demonstrated that fertilization with a complex fertilizer did not have an overall influence on the number of species, indicating that the re-vegetation of extracted peatlands is more controlled by moisture conditions than by the availability of nutrients or propagules arrival.