Towards developing the next generation of the carbon budget model of the Canadian forest sector (CBM-CFS) by including non-disturbance factors

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CBM-CFS3 is the current version used to estimate Canada's managed forest carbon budget for reporting to the United Nations Framework Convention on Climate Change (UNFCCC) and to assist in formulating forest management options in Canada's effort to cope with climate change. The model is based on forest inventory data with complete consideration of all major carbon cycle components. The core of the model is a set of volume-age curves derived from inventory and plot-level forest growth and yield data from across Canada. These curves capture the general pattern of past forest growth but do not account for interannual variations in climate nor can they, by themselves, respond to projected future changes in climate and atmospheric composition. The Integrated Terrestrial Ecosystem Carbon Model (InTEC) makes use of the forest age structure and disturbance data compiled by CFS researchers and estimates forest growth and all other major carbon cycle components using a process-based approach. The strength of this model lies in its integration of both disturbance (fire, insect and harvest) and non-disturbance (climate, C02 and nitrogen deposition) effects on the carbon cycle. The weakness of the model may be the lack of validation of the key curves that define net primary production (NPP) over age and affect regrowth estimation after disturbance. The proposed research aims at improving both CBM-CFS and InTEC models by combining their strengths and making both models more comprehensive. Our first priority will be to enhance the current version of CBM-CFS3 with a non-disturbance module from InTEC to simulate the effects of climate variability and the trends of long-term changes in atmospheric C02 and nitrogen inputs on undisturbed and regrowing forests. We will also use an existing dynamic vegetation model to capture potential responses of vegetation species and structure to climate change. These new capabilities in support the development of the next generation CBM-CFS (Version 4) will improve the estimation of Canada's forest carbon budget for reporting purposes and enhance the ability to support policy analyses of climate mitigation and adaptation strategies in the Canadian forest sector.