Nitrogen retention by peatland buffer areas at six forested catchments in southern and central Finland

Abstract

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 (NH 4 NO 3 -N) solution into the inflow waters of the buffers once (one area) or twice (five areas) during a period of 4-6 years. Except for the first N addition in one area, the three largest buffer areas (relative size [ 1%) retained the added inorganic N almost completely; their retention efficiencies during the year of addition were [93% for both NO 3 -N and NH 4 -N. Two of the three small buffers (relative size \ 0.25%) were also able to reduce inorganic N from the through-flow waters effectively; their retention capacities for inorganic nitrogen varied between 58 and 89%. However, one small buffer area had a retention capacity of only \20%. The factors contributing to efficient N retention were hydrological load during N addition, relative size of the buffer area, and its length, i.e. the distance between the inflow and outflow points. If there was any release of the added N, it mostly occurred within a relatively short-time period (\100 days) after the treatment. The buffer areas appeared to be efficient and longterm sinks for inorganic nitrogen because the release of N during the 2-4 years after N addition was minor.

Nitrogen and dissolved organic carbon (DOC) losses from an artificially drained grassland on organic soils

“…Diffuse nutrient pollution has been found to be a major obstacle to this goal. As nitrate is effectively reduced under wet conditions (Cabezas et al, 2012), re-wetting peatlands has been suggested as a measure to both reduce diffuse pollution originating from degraded peatlands themselves and to clean nutrient-rich water from upstream areas (Davidsson et al, 2002;Trepel, 2010;Vikman et al, 2010). Especially strongly degraded peat seems to have a high denitrification and N retention potential when re-wetted (Cabezas et al, 2012;Davidsson et al, 2002), although other studies have found ongoing mineralisation under these conditions (Olde Venterink et al, 2002).…”

Methane-Cycling Microbial Communities and Methane Emission in Natural and Restored Peatlands

“…The sites receive outflow water from the surrounding forested catchment (29,36). Restoration of the drained peatlands was carried out 10 to 12 years before our study by filling in the drainage ditches with peat.…”

Restoration of ecosystem structure and function in boreal spruce swamp forests

“…At present, spruce swamp forests are also restored in protected areas on private land and in commercial forests (Government of Finland 2008). Concurrently, spruce swamp forests have been experimentally rewetted to be used as buffer zones for runoff waters from areas of intensive forestry to reduce concentrations of organic matter, nitrogen and phosphorus (Nieminen et al 2005ab, Väänänen et al 2008, Vikman et al 2010.…”

“…If rewetting ceases the high CO2 emissions from old peat measured in drained sites (Ojanen et al 2013), significant carbon benefits are expected -but only if the decreased CO2 emissions are not counteracted by increased CH4 emissions from the blocked ditches and other new wet habitats (Cooper et al 2014, Koskinen et al 2012. Spruce swamp forests rewetted as buffer zones for runoff waters have functioned as efficient sinks for dissolved organic matter (Nieminen et al 2005b) and, after more than six years after rewetting, for phosphorus (Väänänen et al 2008) and nitrogen (Vikman et al 2010). During the first (seven) years after rewetting though, rewetting of spruce swamp forest may increase leaching of phosphorus, nitrogen and total organic carbon (Nieminen et al 2005a, Koskinen et al 2011.…”