ACCOUNTING FOR BIOLOGICAL AND ANTHROPOGENIC FACTORS IN NATIONAL LAND-BASE CARBON BUDGETS

Efforts to quantify net greenhouse gas emissions at the national scale , as required by the United Nations Framework Convention on Climate Ch ange, must include both industrial emissions and the net flux associat ed with the land base. In this study, data on current land use, rates of land-cover change, forest harvest levels, and wildfire extent were analyzed under a common framework for three countries in order to comp are net CO2-carbon flux, and to identify key research areas, In the Fo rmer Soviet Union (FSU) and the conterminous United States (US), the s tand age-class distribution on the forested land and the rate of loggi ng tended to be the most important factors in the land-base flux, wher eas in Brazil the rate of land-cover change and the vegetation regrowt h in secondary forests on abandoned agricultural or grazing land were critical. The areas of greatest uncertainty for the FSU and US analyse s related to the rates of woody debris and soil organic matter accumul ation and to limitations in the age-class based inventory data availab le. In Brazil, the initial biomass in forests subject to deforestation , and the area of recovering secondary forest, were identified as impo rtant research issues. Continued database development, and close atten tion to methodologies for quantifying carbon flux, will be necessary i f carbon budget assessments are to be of use to the policy community.