Monitoring Carbon Stock Changes in European Forests Using Forest Inventory Data

Abstract

The forest carbon stock in Europe is large and changes in it may contribute notably to atmospheric CO 2 concentration. The area of forested land in Europe is about 1,000 million ha, which is about 47% of the land area (e.g. MCPFE 2003). The largest part, more than 800 million ha, of the forests in Europe is located in the Russian Federation, whereas the forested area of EU15 is 137 million ha. The percentage of forested land varies considerably between counties ranging from 68% in Finland and Sweden to 1% in Iceland. In the forests of Europe (excluding Russia), the carbon stock of the vegetation was estimated to be about 8,000 Tg (Nabuurs et al. 1997; Goodale et al. 2002). Estimates of the soil carbon stocks range from 5,000 to 14,000 Tg and are evidently more uncertain than the estimated carbon stocks of the vegetation (Goodale et al. 2002; Liski et al. 2002; Nabuurs et al. 2003). Current estimates of the changes in the carbon stock of vegetation in Europe (excluding Russia) range from 50 to 100 Tg C year, and the changes in the soil range from 13 to 61 Tg C year, depending on the methods applied as well as on the reference area and period (Goodale et al. 2002; Liski et al. 2002; Karjalainen et al. 2003; Nabuurs et al. 2003). In general, large carbon stocks of peatlands soils are not fully accounted in these studies, because of the lack of representative data and/or models. The changes in the carbon stock of forested areas are partly due to annual variation in net primary production (NPP) and soil respiration, both resulting from climatic variation (Ciais et al. 2005). Furthermore, most of the annual changes in the forest carbon stock are the result of variation in commercial harvests and natural disturbances (Kauppi et al. 1992; UNECE 2000; Nabuurs et al. 2003). In general, the role of natural disturbance has been marginal in comparison to magnitude of commercial harvests in Europe. Exceptionally severe storms in 1999 reduced the carbon sink of biomass in that year (by 52 Tg C), but the increasing trend in the net carbon sink in Europe was only briefly interrupted by these large-scale disturbances (Nabuurs et al. 2003). Under future climatic conditions, the frequency of largescale disturbances may, however, increase remarkably and they may also play a larger role in Europe’s forests.