HYDROCHEMICAL IMPACTS SET CONSTRAINTS ON MIRE RESTORATION

摘要

About 40 000 ha of mires in the Finnish nature conservation network have been drained by landowners before final inclusion to nature reserves. As a rule, these areas need active restoration to eventually regain the original biodiversity. Hydrological monitoring in sites to be restored was initiated in 1997 in the Seitseminen National Park in a project co-financed by LIFE Nature. The aims of the monitoring included quantification of the water quality impacts of restoration in the downstream watercourses. The hypothesis was that in the long run, water quality would approach that in the natural state, but in the short term, adverse impacts might be expected, since restoration is severely changing the conditions for the forest vegetation, occupying the drained mires after decades in the ditched state. The main adverse short-term impact proved to be the greatly increased leaching of phosphorus. Also the leaching of dissolved organic carbon is increased due to restoration measures, and may to take a longer period to return to pre-restoration values. The short-term adverse impacts of mire restoration should carefully be considered when planning the restoration strategy and actual measures in different sites.