Adding nitrogen to coniferous forests on mineral soils will increase stem-wood growth in most boreal forests. The addition of nitrogen affects soils and waters as well. This investigation was conducted to evaluate the long-term effects of nitrogen fertilization at different intensities on soil chemistry in nitrogen-limited ecosystems. The study was performed at three experimental sites that were originally established around 1980 in Scots pine ( Pinus sylvestris L.) stands. Fertilization regimes with applications ranging from conceivable commercial rates to very intensive rates (3× 150 kg N·ha–1 up to 12× 150 kg N·ha–1) had been applied. Samples were collected from the FH horizon at all sites and 0–20 cm in the mineral soil at two sites and analyzed for pH and major nutrients. The carbon to nitrogen ratio in the FH horizon decreased with increasing total nitrogen application, while the concentrations and contents of nitrogen and exchangeable magnesium and phosphorus increased. The concentration and contents of exchangeable potassium decreased in both the FH horizon and the mineral soil. In general, larger effects on soil chemistry were observed with increasing fertilization intensity.
Long-term effects of fire and harvest on carbon stocks of boreal forests in northeastern China
