Estimating the changes in tree carbon stocks in Galician forests (NW Spain) between 1972 and 2009

Abstract Almost 50% of the land in Galicia (NW Spain) is covered by forest (minimum area of land of 1 ha with tree crown cover of more than 10%) and the region is the top timber–producing area in Spain. Regional changes in forest live tree biomass and carbon stocks were estimated from National Forest Inventory (NFI) data covering almost 40 years, i.e. between NFI-1 (1972) and NFI–4 (2009). Carbon stocks were estimated from biomass of different tree species and components, including roots. Biomass equations were applied to the tree stock data for different species and diameter classes. The biomass increased in all species or groups for the period considered. However, although the biomass of softwood species (mainly Pinus spp.) increased, because of the increase in the number of trees belonging to the largest diameter classes (DC), the balance of the number of small trees (DC