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

This paper presents a first approximation of net CO2 fluxes from mineral soil due to land use, land-use changes and forestry (LULUCF) activities in Brazil for the periods 1970-90 and 1975-95. The methodology employed is an adaptation of the approach proposed by the IPCC in 'Revised 1996 guidelines for national greenhouse gas inventories', which is based on the variations in soil C stocks as a function of changes in land-use activities. The calculation was done separately for each Brazilian state and subsequently summarized 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 and 5.5 g CO2 m(-2) year(-1) for the 1975-95 period. Within each administrative region, considerable differences in the yearly emission rates between the states could be observed. Several sources of uncertainties could be identified. The most important uncertainties were linked to the impact factor values, which represent changes in native C stock associated with conversion of the native vegetation to agricultural use.