Abstract

Changes in disturbance regimes, both natural and anthropogenic, will be an important mechanism by which northern ecosystems respond to climate change, and are an important feedback mechanism in changing ecosystem processes. A forest ecosystem model, EFIMOD, was applied to the jack pine (Pinus banksiana Lamb.) stands in Central Canada to simulate the influence of climate warming, fire, insects and harvesting on jack pine productivity and pools of soil carbon (C). For the climate change simulations, temperature and precipitation prediction data from three General Circulation Models (GCMs) were used: the Canadian Climate Centre for Modelling and Analysis, CGCM2; the UK Hadley Centre, HadCM3; and the Australian CSIRO Mark 2 GCM. In all three of these scenarios, whole trees biomass increased, whereas the soil organic C pool consistently decreased. The CSIRO and CGCM scenarios had the strongest affect on biomass, soil, and ecosystem processes (net primary productivity, soil respiration, and net ecosystem productivity). Assessing the net ecosystem productivity over 150 years for jack pine stands shows a C sink under different disturbance regimes: ‘no disturbances >harvest-fire > two fires > insect attack > harvesting > fire-harvest’ ; and net carbon source under a four fires scenario. The disturbance frequency was found to have a strong and lasting influence on the dynamics of the C stocks, and a direct effect on C source/sink relationship. Soil nitrogen content, which reflect the productivity potential, modify the effect of climate change and disturbances.