Factors influencing ammonia pollution effects on Scots pine stands

Both field and controlled condition experiments have shown sensitivity of conifers for exposures to ammonia. Till now more precise mechanisms of that effect are poorly understood due to scarce longer-term data especially concerning this phenomenon in varying climatic conditions. 1994-2002 year study was aimed at evaluation of a nitrogen fertilizer factory effects on Scots pine stands located within a distance of 0.5-22 km from the factory. Sites were compared according to the concentration of air gases also tree and needle morphological characteristics, needle surface quality, nutritional state, content of free amino acids and cell wall components. Aerial NO2 and NH3 concentrations were determined in sampling sites of pine. In the period of investigation along the transect ammonia concentrations ranged between 4.2 and 42.5 μg m-3, for nitrogen dioxide gradient was smaller and ranged between 2.2 and 5.4 μg m-3. In May-June period concentrations of ammonia were always higher than in August-September, while for nitrogen dioxide situation was opposite. Summer droughts have caused changes in dispersion of NH3. The biggest differences between sites were found according to the nitrogen, free arginine and lignine amount in the needles of Scots pine. In the needles of pines growing under the influence of the highest ammonia pollution elevated concentrations of free arginine, nitrogen and decreased amount of lignine were determined. Along transect decreased concentrations of nitrogen, calcium and magnesium in the new needles grown in 2002 year can not be attributed to the effect of pollution and might reflect consequence of summer drought. For long time (1991-2000) observed differences in the structural surface area of the needles sampled from the trees along ammonia gradient were not documented after 2002 summer. Cluster analyses have shown that values of selected parameters of the needles reflect air pollutant concentrations in sampling sites. [...]Vytauto Didžiojo universiteta