Leaching of nitrogen from a forest catchment at s�der�sen in southern Sweden

Abstract

Water balance and leaching of plant nutrients, with special reference to N, were described for a 46-ha catchment consisting mainly of coniferous forest (one third of it clear-cut) during the period January 1982-August 1988. The atmospheric N load in this region is high compared with most other parts of Scandinavia. On average, annual N leaching amounted to 9.5 kg ha−1 in the form of NO3-N (83%), org-N (15%) and NH4-N (2%). The highest monthly rate of N transport observed was 3.9 kg ha−1. The NO3-N levels in groundwater in the 60-yr-old coniferous stand ranged from 0.5 to 3.1 mg L−1. The effect of clear-cutting on groundwater-NO3-N levels lasted 4 yr. The highest annual NO3-N transport from the clear-cut area observed was 18 kg ha−1. The groundwater in the spruce forest was very acidic (pH=4.3) in contrast to the stream water (pH=6.3). The relatively higher pH-value of the stream water was probably a result of chemical and biological processes occurring in the highly humified, periodically waterlogged peat soil (alder swamp) in the vicinity of the small stream.