CO2 emission from mineral soils following land-cover change in Brazil

This paper presents a first approximation of net CO2 fluxes from mineral so il due to land use, land-use changes and forestry (LULUCF) activities in Br azil for the periods 1970-90 and 1975-95. The methodology employed is an ad aptation of the approach proposed by the IPCC in 'Revised 1996 guidelines f or national greenhouse gas inventories', which is based on the variations i n soil C stocks as a function of changes in land-use activities. The calcul ation was done separately for each Brazilian state and subsequently summari zed for all of Brazil. The annual fluxes for Brazil indicate a net emission of CO2 to the atmosphere, which decreased from 93.3 Tg CO2 for the period 1970-90 to 46.4 Tg CO2 for the period 1975-95. This corresponded to yearly net emission rates of 11.0 g CO2 m(-2) year m(-1) for the 1970-90 period an d 5.5 g CO2 m(-2) year(-1) for the 1975-95 period. Within each administrati ve region, considerable differences in the yearly emission rates between th e states could be observed. Several sources of uncertainties could be ident ified. The most important uncertainties were linked to the impact factor va lues, which represent changes in native C stock associated with conversion of the native vegetation to agricultural use.