On the distribution of Nectria canker of beech in natural regenerations: influence of shelterwood and site factors

摘要

The distribution of beech canker was surveyed in the natural regeneration of 111 beech stands in 11 forest districts of Baden-Wurttemberg. 801 sample plots comprising some 60,000 tree individuals were monitored. Beech canker was found in each forest district and in 75% of the stands. However, the disease incidence rarely reached a level of economical importance. The natural regeneration was significantly more affected by beech canker when growing under a diseased beech shelterwood.However, the impact of the density of the canopy itself, presumably corresponding with light intensity, was not evident. In mixed stands the disease incidence was lower than in pure beech stands. Forest stands at lower altitudes (up to ca. 450 m above sea level) were more affected. Correspondingly, disease incidence more than tripled in the warmer and dryer areas.