Effects of air pollution and climatic factors on Norway spruce forests in the Orlické hory Mts. (Czech Republic), 1979–2014

Abstract

The area of the Orlicke hory Mts. has been characterised by decline and disturbances of Norway spruce (Picea abies/L./Karst.) stands since the 1980s. Currently, only three permanent research plots have been preserved from the original sixteen established plots in this region. In the present study, the health status, as indicated by defoliation, mortality, and stem radial growth, was studied in the peaty and climax spruce ecosystems in the upper elevations of the mountains from 1979 to 2014. This health status was correlated with ambient air pollution (SO2) as well as climate factors (temperature and precipitation). The health status of individual trees on the plots was determined by evaluation of the foliage status, and tree vitality was evaluated by measuring stem radial growth increment. Stress factor analysis showed that high air pollutant concentrations predisposed Norway spruce to stress from climatic events (drought, temperature changes), leading to forest decline. The most serious damage can be attributed to the combination of chemical and climatic stress. Stands with lowered vitality were attacked by secondary biotic pests (particularly bark beetle), resulting in rapid tree mortality. The damage process is marked not only by higher mortality, but also by chlorosis and necrosis of the needles. The stabilised trend in health status of the spruce stands was registered since approximately 1990s. In terms of climatic factors, the weather in June had the most visible influence on radial increment. Low temperatures and high precipitation were the limiting factors for radial growth in studied mountain area.