NITREX project - Gårdsjøn. Status report for 1988-1990

At the NITREX site at Gårdsjøn, Sweden, nitrogen deposition will be experimentally increased to an entire forested catchment to study the potential for nitrogen saturation. Investigations include regular sampling of precipitation, thoughfall and runoff and compilation of input-output beugets. Short-term experiments of toxicity of the runoff water to fish are also underway. Studies of vegetation and soils are centered around three vegetation types characteristic of the catchments. Plots have been selected on the basis of soil and vegetation maps of the three catchments. Regular measurements include (1) volume and chemical composition of soil solution, (2) soil temperature, (3) chemical composition of needles, (4) amount and chemical composition of litterfall, and (5) soil moisture. In addition studies of mineralization, fine roots, and mycorrhiza are being conducted. Nitrogen addition will begin in April 1991. The NITREX data from Gårdsjøn will be combined with similar data from the other NITREX sites throughout Europe

Gårdsjön Status Report for 1991-1992: The first Year of Treatment

Nitrogen addition weekly to catchment G2 at Gårdsjön began April 1991. During the first year of treatment a total of 230 meq/m²yr NH4No3 was added in 33 mm of water plus 90 meq/m²/yr deposited in 631 mm throughfall. Runoff contained significantly higher concentrations of No3 (but not NH4) beginning in November 1991. No respons was seen during the growing season. None of the other components and processes (soil solution, mineralization, fine-roots, mycorrhiza and vegetation) studied as part of NITREX showed significant response during the first year of treatment