Long-term effect of climate and air pollution on health status and growth of Picea abies (L.) Karst. peaty forests in the Black Triangle region

The Jizerské hory Mts. (the Czech Republic) are part of the Black Triangle region strongly af- fected by a decline and dieback of Norway spruce (Picea abies [L.] Karst.) stands since the 1970s. In the studied peaty spruce stands in the summit parts of the Jizerské hory Mts., the health status, radial growth and foliar nutrient content in relation to air pollution (SO2, NOX and O3) and climate factors (temperature, precipitation) were investigated in 1960–2015. A considerable disturbance of the stand structure induced by an increased mortality was observed in 1981–1983 when more than a half of the tree individuals died. Severe defoliation occurred in 1981 as a consequence of the synergic effects of air pollution, winter des- iccation and spruce bark beetle outbreak, as well as in 2015 due to the drought and high temperatures. Tree ring analyses indicated significant growth depression in 1979–1987, a period of the highest SO2 load, and in 2010–2015. Foliation and diameter increment were significantly influenced by SO2 and NOX con- centrations, the maximum daily concentration being the most negative factor; no significant correlation of the ozone exposure was detected, though. Foliar analyses also document significant negative impacts of air pollutants on the nutrient status of forest stands, mainly in the increase of the sulphur level. Since 1990, a significant increase in calcium and magnesium has been observed, as a result of forest liming. Interaction between radial growth and temperature was stronger compared to precipitation. Low temper- atures and high precipitation in growing season were the limiting factors for radial growth in waterlogged mountain areas