Sakari Sarkkola

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Temporal trends in stream water total organic carbon (TOC) concentration and export were studied in 8 forested headwater catchments situated in eastern Finland. The Seasonal Kendall test was conducted to identify the trends and a mixed model regression analysis was used to describe how catchment characteristics and hydrometeorological variables (e.g.(More)
Observations of increased water colour have been made in lakes and rivers all across the northern mid-latitudes of Europe and North America, particularly during the last 10-20 yr. This water browning or brownification has been attributed to the increased organic carbon concentrations due to climate change and decreased acid atmospheric deposition. Given(More)
We studied the nitrogen retention capacity of six peatland buffer areas constructed in forested catchments in southern and central Finland. The buffers (0.1–4.9% of the total catchment area) were either undrained mires or drained peatlands rewetted 4–7 years before the present study. The N retention capacity was studied by adding ammonium nitrate (NH4NO3–N)(More)
Information on the variation in soil element concentrations at different spatial scales is needed for, e.g., designing efficient sampling strategies, upscaling the processes related to carbon cycling, and planning land use and management. In spite of intensive land use, such information concerning peat soils is still scarce. We analyzed the variation in(More)
Peatlands are becoming increasingly used as buffer areas to reduce nutrient transport into watercourses, but knowledge on the dynamics of the element cycle, particularly in gas phase is scant. We investigated if peatland buffer areas significantly contribute to emissions of nitrous oxide (N2O) from forested catchments. We used an artificial addition of 150(More)
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(More)
The current understanding, based on previous studies, is that increased discharge nutrient concentrations from boreal peatlands drained for forestry return to similar levels as those of pristine peatlands within about 20years after their drainage. As an implicit consequence of this finding, it has been assumed that there are no long-term increasing trends(More)
About 15 million hectares of peat soils have been drained for forestry in temperate and boreal zones. Increasing interest in wood biomass as a source of bioenergy has led to more intensive harvests also in peatland forests. These harvestings remove branches, needles, and stump/root systems that would earlier have remained on-site. However, in drained(More)
Drained peatlands are an important source of forest biomass in boreal regions and ditch network maintenance (DNM) operations may be needed to restore the drainage functions of ditches. By reviewing the available literature, as well as utilizing an existing hydrological model and analyzing the characteristics of eroded sediments, we assessed the impacts of(More)
1) Natural Resources Institute Finland, P.O. Box 18, FI-01301 Vantaa, Finland (*corresponding author’s e-mail: mika.nieminen@luke.fi) 2) Department of Forest Sciences, P.O. Box 27, FI-00014, University of Helsinki, Finland 3) Natural Resources Institute Finland, P.O. Box 68, FI-80101 Joensuu, Finland 4) Trinity College Dublin, School of Engineering, Trinity(More)