Articles | Volume 9, issue 6
Hydrol. Earth Syst. Sci., 9, 657–674, 2005
https://doi.org/10.5194/hess-9-657-2005

Special issue: Water and chemical fluxes through catchments

Hydrol. Earth Syst. Sci., 9, 657–674, 2005
https://doi.org/10.5194/hess-9-657-2005

  31 Dec 2005

31 Dec 2005

Water and nitrogen processes along a typical water flowpath and streamwater exports from a forested catchment and changes after clear-cutting: a modelling study

A. Laurén1, L. Finér1, H. Koivusalo2, T. Kokkonen2, T. Karvonen2, S. Kellomäki3, H. Mannerkoski3, and M. Ahtiainen4 A. Laurén et al.
  • 1Finnish Forest Research Institute, Joensuu Research Centre, Yliopistokatu 6, P.O. Box 68 FIN-80101 Joensuu, Finnland
  • 2Laboratory of Water Resources, Helsinki University of Technology, P.O. Box 5300 FIN-02015 TKK, Finnland
  • 3University of Joensuu, Faculty of Forestry, P.O. Box 111, FIN-80101 Joensuu, Finnland
  • 4North Karelia Regional Environment Centre, P.O. Box 69 FIN-80101 Joensuu, Finnland

Abstract. A two dimensional model, FEMMA, to describe water and nitrogen (N) fluxes within and from a forested first-order catchment (Kangasvaara in Eastern Finland) was constructed by linking the most significant processes affecting the fluxes of water, ammonium, nitrate and dissolved organic nitrogen along a hillslope from the water divide to the stream. The hillslope represents the average flowpath of water in the catchment and the model was used to estimate the N fluxes for a catchment in eastern Finland before and after clear-cutting. The simulated results were in reasonable agreement with the nitrate, dissolved organic N and dissolved total N measurements from the study catchment and with other results in the literature. According to the simulations, the major sinks of N after clear-cutting were immobilisation by soil microbes, uptake by ground vegetation and sorption to soil. These sinks increased downslope from the clear-cut area, indicating the importance of an uncut buffer zone between the stream and the clear-cut area in reducing N exports. The buffer zone retained 76% of the N flux coming from the clear-cut area. Nitrification was a key process in controlling the N export after clear-cutting and N increases were mainly as nitrate. Most of the annual N export took place during the spring flood, when uptake of N by plants was minimal.