Dendroecological investigation of the vitality of Common Beech (Fagus sylvatica L.) in mixed mountain forests of the Northern Alps (South Bavaria)

Time series of radial growth and crown condition were used to assess the vitality of Common Beech (Fagus sylvatica L.) in mixed mountain forests of the Bavarian Alps. The investigation plots are located in three altitudinal belts at the mountains Kranzhorn and Laber. Sites at Kranzhorn are permanent monitoring plots since 1985, where beech show a high and, especially since 1996, at high altitudes increasing degree of crown transparency. No significant and ecological sensible relationship was found neither between crown condition data and weather, nor between crown condition data and water balance parameters. Tree-ring analyses revealed repeated growth depressions during the last decades starting at the end of the 1970s. Their intensity and duration increased with altitude. Climate–growth analyses carried out for the period 1931–2003 point to a temperature dependence of growth. Cool and short vegetation periods and especially late frost events appear as growth-limiting factors. Even in dry and warm years no serious growth-relevant water deficiency occurred. Neither weather fluctuations and extreme events, evaluated by different methods, nor age- or site-related differences provided sufficient explanations for growth disturbances and vitality loss in the last decades. Hence, further investigations are necessary to explain vitality loss, damage and destabilization of Common Beech in mixed mountain forest of Southern Germany. At Kranzhorn, strong relations between radial growth and defoliation were found, indicating the importance of long-term observation and monitoring data for these purposes.