Woody biomass and annual production across a latitudinal gradient in Northern Scots pine (Pinus sylvestris) forests

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.