Substrate quality and spontaneous revegetation of extracted peatland: case study of an abandoned Polish mountain bog

If peatland is left without any restoration treatments after mechanical peat extraction ceases, the process of secondary transformation of peat continues. The resulting changes in peat properties severely impede the recovery of vegetation on cutover peatland. The aim of this study was to assess how secondary transformation of peat affects spontaneous revegetation, and the relative importance of different factors in controlling the re-establishment of raised bog species on previously cutover peat surfaces. The study was conducted on two sectors of a raised bog in southern Poland where peat extraction ended either 20 or 30 years ago. Where the residual peat layer was thin (~ 40 cm or less) and the water table often dropped into the mineral substratum, the development of vascular plants (including trees) was favoured, and this further promoted the secondary transformation of peat. In such locations the vegetation tended towards a pine and birch community. Revegetation by Sphagnum and other raised bog species (Eriophorum vaginatum, Vaccinium uliginosum, Ledum palustre, Oxycoccus palustris) was associated with thicker residual peat and higher water table level which, in turn, were strongly correlated with hydrophysical properties of the soil. A species - environmental factor redundancy analysis (RDA) showed that any single factor (of those considered) was not important in determining the revegetation pattern, because of their intercorrelations. However, water table level appeared to be the most important abiotic factor in determining the degree of soil aeration and, consequently, the stage of secondary transformation attained by the peat