Effectiveness of restoration of a degraded shallow mountain fen after five years

As a contribution to improving understanding of the mechanisms and relationships that exist within shallow peatland ecosystems, we report the results of monitoring five-years’ recovery after restoration of a forestry-drained sloping rich fen site in the Central Sudetes in south-west Poland. Over the last 100 years, drainage ditches installed for forestry management purposes have affected the hydrology, soil and vegetation of this site. Spruce stands were present until 2010, when restoration started with blocking of ditches and clearcutting/removal of trees. The main objective of our study was to determine the effects of these restoration activities on aspects of hydrology and soil condition. We hypothesised that the five years following restoration could provide sufficient time to improve: 1) water table level and water quality, and 2) the physical and chemical properties of the organic soil. Restoration had a positive effect on water table level as early as two years after implementation of drain blocking and reduction of tree cover. However, five years was not sufficient time to reverse the decline in water quality. The concentrations of labile carbon forms in water, as well as water colour (Abs400), were similar in 2010 and 2015. Due to peatland rewetting and peat swelling a decrease in peat bulk density was observed. However, this outcome was identified only in the bottom organic soil horizons. This, in turn, affected the thickness of the peat layer and the altitude of the soil surface. Five years of recovery is insufficient to stop the mineralisation of organic matter, as indicated by lower TOC/TN values, slightly higher concentrations of labile forms of carbon, and the W1 index of secondary transformation.