Changes of Abies alba crown state and stand quality class in the Sudety Mountains

Sudeteny Mts. are a region where the level of industrial air pollution was very high due to brown coal combustion. In this paper I presents the assessments concerning the fir stand quality class and crown vitality.The study were carried out between 1999 and 2001 and supplemented with studies made in 1997 and 2005. My conclusions are based on measurements of 3529 fir trees representing 481 populations of this species in different parts of the Sudety Mts. The stand quality class of the fir in the Sudety Mts. are better than expected but about 0,5 degree lower than in the Carpathians. Our results confirm the reports concerning the strong and very strong damage of fir crowns in the Sudety Mts. in the 1990’s. It was calculated that the average fir in the Sudety Mts. stands has a primary crown with a length that is approximately 19% of the total tree height and which is damaged in approximately 36%. At approximately 23% of the total height the average fir develops a regeneration crown. An additional factor which contributed to fir damage was their frequent presence in thinned stands. In these places the process of crown reconstruction from a wide to a denser is observed. In the recent years the level of industrial pollution in the Sudety Mts. has been strongly reduced. This particularly concerns sulphur oxides. This has contributed to the improvement of the crown health of the studied species, but the crown regeneration is slower than the trunk diameter increment. The crown damages have so far been proportional to the altitude. Trees which grow in stands located in lower areas have healthier crowns. Trees which grow in broken canopy and on hilltops are more vulnerable to the impact of pollution carried by wind and fog. The severe damage to the top parts of the crown has a negative effect on the cone crop of the fir.