Nitrate leaching from a felled Sitka spruce plantation in Beddgelert Forest, North Wales

Abstract. Soil water samples from five horizons in a stagnopodzol were collected regularly over a five-year period in a Sitka spruce plantation at Beddgelert Forest, North Wales. Samples were analysed for nitrate-N and ammonium-N. After felling, inorganic-N concentrations increased markedly in the C horizon, generally decreased in the surface horizons and showed little change in the E and Bs horizons. Fluxes through the C horizon increased after felling from 10 to 70 kg N ha^-1 a^-1, the latter being equivalent to leaching losses in intensive lowland agricultural systems. Trends in concentration and flux were attributed to seasonal temperature and rainfall variations.
Nitrate-N dominated the dissolved inorganic-N, especially in the lower horizons. Nitrification was obviously active, despite the acid soil. Nitrate leaching losses occurred, even beneath the standing crop. On felling, cessation of nitrogen uptake allowed substantially more nitrate to be leached as no alternative sink was immediately available.