ZLV Online

The aim of the article is to evaluate changes in the health state and nutrition level of young forest stands caused by the historical development of the air pollution load. Nineteen research plots were selected on the Jizera Mts. (Jizerské hory, Czech Republic) plateau, within complexes of young Norway spruce stands. Since 1993 tree crown defoliation and height increment have been assessed every year after the vegetation season. Sampling of needles for nutrient analyses was done every autumn together with the crown condition assessment. Soil samples were taken in 1995, 1999, 2003 and 2009. Samples of the upper organic layer and of the mineral soil in 0–30 cm depth were taken separately. Samples of assimilation organs, humus and mineral soil were prepared and analyzed according to the standard ICP Forests methods. Long term results have confirmed that the health state, expressed in crown defoliation, is affected by combination of various stress factors (air pollution, frost and temperature, nutrition supply). Health status has significantly improved and crown defoliation values got comparable to those of other forest regions in the Czech Republic. There was found a significant dependence between crown defoliation and height increment as well as the significant dependence of crown defoliation on concentrations of elements in the needles. Foliar concentrations of stress elements (sulfur, fluorine), and potassium were positively correlated with the crown defoliation, the nitrogen and magnesium content displayed the negative dependence. Foliar analysis has demonstrated a significant decrease in air pollution load, and a problem with insufficient uptake of phosphorus has also been indicated. Soil analyses confirmed the fact that the soil environment is acidic and the amounts of accessible phosphorus, exchangeable magnesium and calcium are significantly deficient in the mineral soil. The persistent problem in nutrition may adversely affect growth and development of the health status of the monitored spruce stands in the future.