Hordo, M., Metslaid, S. and Kiviste, A. 2009. Response of Scots Pine (Pinus sylvestris L.) Radial Growth to Climate Factors in Estonia.   Baltic Forestry, 15 (2): 195-205

The following research paper analyzes Scots pine (Pinus sylvestris L.) radial growth responses to climatic factors in mesotrophic and heath forest site types in Estonia. Increment cores from 889 trees from 119 plots of the network of research plots were used and chronologies for mesotrophic and heath forest site types of Scots pine were constructed. The relationship between climatic factors and the radial growth of Scots pine was characterized by correlation coefficient; also pointer year analysis, Cropper method was applied to single tree series. Cropper values were calculated; extreme negative and positive pointer years were identified. According to analyses, 1940 and 1985 were the most significant negative pointer years among different sites; and significant positive years were 1945, 1946, 1989, and 1990. Extreme Cropper values indicated significant positive correlation with the monthly mean temperature in winter (January, February) and early spring (March, April) before a growing season; also with the mean annual temperature and the mean temperature of the vegetation period (from April to September). Significant negative correlation was found between the extreme Cropper value and the precipitation of the previous year August. Therefore, temperature can be considered as the most important single factor of growth activity. Pointer year analyses confirmed that severe winters, cool springs and dry summer conditions are the main causes for the sharp decrease in radial growth.

Key words: climate variables, pointer years, radial growth, Scots pine, tree-ring chronology