Restoration of nutrient-rich forestry-drained peatlands poses a risk for high exports of dissolved organic carbon, nitrogen, and phosphorus

Markku Koskinen; Teemu Tahvanainen; Sakari Sarkkola; Meseret Walle Menberu; Ari Laurén; Tapani Sallantaus; Hannu Marttila; Anna-Kaisa Ronkanen; Miia Parviainen; Anne Tolvanen; Harri Koivusalo; Mika Nieminen

doi:10.1016/j.scitotenv.2017.02.065

Restoration of nutrient-rich forestry-drained peatlands poses a risk for high exports of dissolved organic carbon, nitrogen, and phosphorus

Sci Total Environ. 2017 May 15:586:858-869. doi: 10.1016/j.scitotenv.2017.02.065. Epub 2017 Feb 16.

Authors

Affiliations

¹ Department of Forest Sciences, University of Helsinki, P.O. Box 27, FI-00014,Finland. Electronic address: markku.koskinen@helsinki.fi.
² Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu campus, P.O. Box 111, FI-80101, Joensuu, Finland.
³ Natural Resources Institute Finland, Latokartanonkaari 9, Helsinki FI-00790, Finland.
⁴ Water Resources and Environmental Engineering Research Unit, University of Oulu, P.O. Box 4300, FI-90014, Oulun yliopisto, Finland.
⁵ Natural Resources Institute Finland, P.O. Box 68, Yliopistokatu 6, Joensuu FI-80101, Finland.
⁶ Finnish Environment Institute, Mechelininkatu 34a, FI-00260 Helsinki, Finland.
⁷ Natural Resources Institute Finland, P.O. Box 413, FI-90014 Oulun yliopisto, Finland.
⁸ Department of Ecology, University of Oulu, P.O. Box 8000, FI-90014, Oulun yliopisto, Finland; Natural Resources Institute Finland, P.O. Box 413, FI-90014 Oulun yliopisto, Finland.
⁹ Department of Built Environment, Aalto University School of Engineering, P.O. Box 15200, FI-00076 Aalto, Finland.

PMID: 28215796
DOI: 10.1016/j.scitotenv.2017.02.065

Abstract

Restoration impact of forestry-drained peatlands on runoff water quality and dissolved organic carbon (DOC) and nutrient export was studied. Eight catchments were included: three mesotrophic (one undrained control, two treatments), two ombrotrophic (one drained control, one treatment) and three oligotrophic catchments (one undrained control, two treatments). Three calibration years and four post-restoration years were included in the data from seven catchments, for which runoff was recorded. For one mesotrophic treatment catchment only one year of pre-restoration and two years of post-restoration water quality data is reported. Restoration was done by filling in and damming the ditches. Water samples were collected monthly-biweekly during the snow-free period; runoff was recorded continuously during the same period. Water quality was estimated for winter using ratios derived from external data. Runoff for non-recorded periods were estimated using the FEMMA model. A high impact on DOC, nitrogen (N) and phosphorus (P) was observed in the mesotrophic catchments, and mostly no significant impact in the nutrient-poor catchments. The DOC load from one catchment exceeded 1000kg (restored-ha)^-1 in the first year; increase of DOC concentration from 50 to 250mgl^-1 was observed in the other mesotrophic treatment catchment. Impact on total nitrogen export of over 30kg (restored-ha)^-1 was observed in one fertile catchment during the first year. An impact of over 5kg (restored-ha)^-1 on ammonium export was observed in one year in the mesotrophic catchment. Impact on P export from the mesotrophic catchment was nearly 5kg P (restored-ha)^-1 in the first year. The results imply that restoration of nutrient-rich forestry-drained peatlands poses significant risk for at least short term elevated loads degrading the water quality in receiving water bodies. Restoration of nutrient-poor peatlands poses a minor risk in comparison. Research is needed regarding the factors behind these risks and how to mitigate them.

Keywords: DOC; Leaching; Nutrients; Peatland forests; Restoration.