Effect of climatic factors on the dynamics of radial increments of Norway spruce, European beech and sessile oak

Correlations of increment indexes with average monthly temperatures and total monthly precipitation were studied on annual ring series of 455 trees of Norway spruce (Picea abies [L.] Karst.), sessile oak (Quercus petrea Liebl.) and European beech (Fagus sylvatica L.). Data on precipitation from the period 1901–2005 and on temperatures from the period 1931–2005 were used. Statistically significant dependences with correlation coefficients in the range of 0.2–0.5 were confirmed. All tree species react positively to precipitation mainly in June and July. An increase in precipitation by 1 mm when compared with the long-term average results in an increase in increment index of spruce almost by 0.13%. This index in oak and beech increases only by a half value of the value for spruce. Precipitation from the second half of the vegetation period of the previous year is also important. Higher temperatures during the vegetation period affect increment changes mostly negatively. With temperature increase by 1°C, when compared with the long-term average, the increment index of trees decreases by about 1–2%.