Forestry effects on water quality

In the Nordic countries, 62-72% of the land area is covered by forests, of which up to 25% are on drained peatlands. In the near future, forest management in this drained peatlands is predicted to increase due to the increasing pressure for using forest resources for industry and/or energy production. Forest and drainage management of peatlands may play an important role in creating still unknown pressure to water quality, specifically by increasing dissolved organic carbon (DOC) and brownification or by increasing nitrogen and phosphorus and eutrophication in boreal aquatic ecosystems. Consequently, there is a need for comprehensive analyses of the effects on inland waters of peatland forest harvesting and drainage management such as ditch cleaning to maintain forest productivity or ditch blocking to restore old drained peatlands. To overcome this lack of scientific knowledge, we have established the experimental ditch management infrastructure, called Trollberget Experimental Area (TEA) in Krycklan. TEA includes the first fully replicated and controlled experimental catchment system based on a BACI approach (before-after and control-impact). The treatments represent the dominant ecosystem types impacted by ditching in Sweden and the boreal zone: 1) hydrological restoration of a drained peatland by rewetting through ditch blocking (catchment R1 and R2), 2) maintaining peatland forest productivity by lowering the water table through ditch cleaning after forest harvest (catchments DC1 and DC3) and 3) leaving these ditches unmanaged (DC2 and DC4). Here, to evaluate the effects of forestry in water quality and the influence on eutrophication and brownification in downstream freshwater ecosystems, we are monitoring DOC, nitrate (NO₃), ammonium (NH₄), phosphate (PO₄) as well as establishing specific experiments to account for change in nutrient limitation and establish possible impacts in ecosystems, such as nutrient diffusing substrate (nds) experiments.