Characterising the effects of high ammonia emission on the growth of Norway spruce

This paper studies the effects of high ammonia emissions and nitrogen deposition on tree growth. Wood cores of 125 Norway spruces were analysed along a transect (800 m) from forest edge to forest interior. The forest edge was exposed to a strong ammonia emission source (poultry farm, less than 50 m). Atmospheric nitrogen bulk deposition, ammonia concentration, soil solution concentration, soil nutrient content, foliar N concentration and C/N ratio of the humus layer were measured at five plots along the transect. The tree growth increment of two clusters of trees close to the forest edge and forest interior was compared. The results indicate extremely high nitrogen load at the forest edge. All nitrogen variables show an `edge effect' with increasing values from forest interior to the forest edge. The growth of nitrogen-influenced spruce trees generally increases. Trees with excessive long-term nitrogen load appear to loose increment after a long-term nitrogen impact. The average gain of increment at the edge appears to be related to the amount of nitrogen emission.