The carbon budget of the Spanish forests

A model for the calculation of anthropogenic CO₂ emissions from perturbed forests (extraordinary emissions) is described. Timber production as well as wildfire statistics are used, and relevant physicochemical parameters are derived from the literature, to calculate the annual amounts of perturbed biomass and extraordinary emissions to the atmosphere from the Spanish forests — including soils — in the years 1960–1990; these emissions increased from 5.3 10⁶ t (metric tons) of carbon in 1970 to 10.6 10⁶ t C in 1990. A sensitivity analysis of the results has been performed to identify the most critical parameters. Contributions of observed timber growth and natural vegetal detritus and soil organic matter to the net forest carbon flux have been estimated to calculate the carbon budget in the Spanish forests between 1966 and 1974, which represents a net gain of carbon, ranging from 9.2 to 18 millions t. Finally, the methods used to calculate biospheric carbon balance and their results are compared and discussed.