C AND N STORAGE IN LIVING TREES WITHIN FINLAND SINCE 1950S

Living biomass contains 45 to 60% carbon and 0.05 to 3% nitrogen, in d ry weight. Like throughout Europe, the amount of living biomass in Fin nish forests has increased on average over the last decades, largely b ecause of changes in forest management. The storage of organic C and N in biomass has also increased. Changes in biomass vary between region s. Data were analysed on changes in the last 30-40 years in C and N st orage in living trees in Finland, subdivided into 20 regions. Tree bio mass increased in 17 regions, and decreased in 3 regions. The storage rate varied between -170 and +480 kg C ha(-1) a(-1), and between -0.5 and + 1.2 kg N ha(-1) a(-1). Nitrogen accumulation in trees was less t han 15% of atmospheric N deposition in all regions. Although the event ual increase of the nitrogen concentration in tree tissues was omitted , it is not possible that living biomass has been the major sink for a tmospheric N deposition to forests. A hypothesis is presented that the main sink is litter layer and organic soil. Carbon can also be accumu lating in soils essentially faster than hitherto estimated in analyses of carbon budgets of European forests.