Scots pine growth trends in Northwestern Kola Peninsula as an indicator of positive changes in the carbon cycle

Growth trends of Scots pine (Pinus sylvestris) at its northernmost extent may be an indicator of changes in the carbon cycle of terrestrial forest ecosystems. Using a method which removed age trends from the data, a time-series analysis of annual radial increment in wood over the last few decades compared with the period of the last registered warming (maximum around 1930-40), revealed elevated growth of 78% for trees 0-20 years old, 56% for trees 21-40 years old, 21% for trees 41-60 years old, and 10% for trees more than 101 years old. Increments of trees in the 61-80 and 81-100 years old age classes from the two periods were similar. The higher rate of growth in recent times occurred despite a decrease in temperature after about 1940 and significant air pollution. During the last century growth of Scots pine increased for trees in all age groups, except for trees in the 81-100 year old age class for which it was constant. The average rates of growth were estimated at 0.016 mm/year for trees in the 0-20 year age class, 0.012 mm/year for the 21-40 year age class, 0.005 mm/year for the 41-60 year age class, 0.008 mm/year for the 61-80 year age class and 0.006 mm/year for trees in the greater than 101 year age class. The growth trends were unstable over time and took place concurrent with increasing oscillations in radial increment. The most probable reasons for the marked increase in radial increment growth of Scots pine in this region are climate warming and higher levels of carbon dioxide. Together these may produce a synergistic effect on growth.