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Hordo, M., Henttonen, H. M., Mäkinen, H., Helama, S. and Kiviste, A. 2011. Annual Growth Variation of Scots Pine in Estonia and Finland.  Baltic Forestry 17 (1): 35 – 49

This study presents the results of a dendrochronological and dendroclimatological study of Scots pine growth on dry sites in Estonia and Finland. Increment cores from two regions in Estonia and from five regions in Finland are used. The cores were collected from living trees nearby permanent research plots in Estonia and from the National Forest Inventory (NFI) plots in Finland. A total of 1024 trees’ radial growth was measured in 551 sample plots. The relationship between two types of standardized index series (regional growth curve RGC and negative exponent curve EXP) and weather parameters derived from daily data was characterized by correlation analysis. According to the location of studied sites (regions), positive correlation of precipitation and negative correlation of temperature (e.g. spring temperatures, drought etc) to the radial growth of Scots pine trees was found. A similar climate impact to the radial growth in mean temperature and the sum of precipitation in August of the previous year was found in several regions (HI, EK, OP, PK), which means that drought could be the main growth limiting factor in several regions. The correlation between spring temperature (mid-March – early-April) and diameter increment seems also to be positive and significant in some regions (HI, EK, EP, OP, SO). Cropper method was applied to pointer year analysis in different regions. According to the analysis, 1967 and 2000 were the most significant positive pointer years in several regions; and 1969 was a negative pointer year in five regions. Therefore, weather prerequisites for tree growth are expected to change gradually from south to north regions.

Key words: correlation analysis, increment cores, permanent research sample plots, NFI, radial growth, biogeography, Cropper method