Changes in the nutrition and health status of young Norway spruce stands in the Krkonoše Mts. in a 17-year period

For 17 Norway spruce stands located in the Krkonoše Mts. in the Czech Republic a long-term assessment of defoliation, height increment, foliage concentration of nutrients (N, P, Ca, K, Mg) and stress elements (S, F) was carried out. The results show a decrease of defoliation and a slight increase of height increment, which occur in accordance with the decreasing concentration of sulphur in spruce needles. However, neither sulphur concentration nor height increment trends are significant, suggesting that both the main pollution abatement and the growth resumption took place already in the 1990's. During the late 1990's the average spruce defoliation was greater than 35%, while since 2007 it has fluctuated between 18 and 25%, which corresponds with the figures for the forest stands located in the other regions of the Czech Republic. The evaluation of single nutrient concentrations detected occasional deficiencies of P and Mg at individual plots. The good N nutrition (> 15 mg N.g-1) in combination with a significantly decreasing trend of P, K and Ca concentrations in Norway spruce needles may potentially constitute a problem in regard to both the future health and the stability of forest stands in the studied region.