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The rate of change of pine radial growth was evaluated for 9 sites of forest located on the latitudinal transect. The average widths of tree rings of Scots pine trees at the ages 20 to 60 years were selected from long-term (70-170 years) measurements collected on the transect sites. The tendency to increasing radial growth noted southward, was associated with increasing growing season temperature and decreasing latitude. The rate of change of radial growth expressed in % per 1°C of average annual temperature and -1°N of latitude equals 2.40% (per 1°C) and 1.22% (per -1° latitude).
History of the Scots pine sites along the Finland-Poland boreal-temperate transect along 25°E longitude, ranging from 50°N-70°N latitude (see Fig. 1 in Breymeyer 2003) was reconstructed using tree-rings. The correlation between the tree-ring index chronologies for the sites was studied. The age of trees at particular sites varies in the range from 66 to 178 years. The youngest trees are growing at the sites FN3 and PL3, the eldest at FN1. At the sites FN1 and PL1, two groups of trees of different age were separated. Correlation analysis revealed significant correlation among the Baltic chronologies. High correlation coefficients were also found between the PL2 site chronology and all the Baltic state chronologies. No positive correlation was detected among the chronologies from the sites in Finland and in Poland.
To better understand how forest growth might be affected by climate, we observed patterns of forest growth (in terms of basal area, diameter, canopy height, and total biomass) in Scots pine forest ecosystems at nine stands along a northern latitudinal gradient (50°N-70°N) crossing Poland, Lithuania, Latvia, Estonia, and Finland. This gradient is characterized by a northward decline in average annual temperature (Δ = c. 9°C) and precipitation (Δ = c. 300mm). Basal area, average diameter, canopy height, and total biomass appear correlated with average annual temperature (P-values range from <0.002 to 0.096), but were not correlated with average annual precipitation. None of the measures of absolute growth or percent growth rates (averaged over four measurement periods) were correlated with temperature or precipitation. A framework for evaluating recent increases in biomass pools in northern systems is given, but data here are of insufficient power to confirm or refute hypotheses of recent increase in production of northern forests.
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