SIMULATING CARBON DYNAMICS ALONG THE BOREAL-FOREST-TRANSECT CASE-STUDY (BFTCS) IN CENTRAL CANADA - 1 - MODEL TESTING

CENTURY 4.0, a simulation model of carbon and nitrogen dynamics of ter restrial ecosystems based on the relationships between climate, soil t exture, plant productivity, decomposition and human management, was te sted against observed data along the boreal forest transect case study (BFTCS) in central Canada. The results show that the simulated averag e aboveground biomass and net N mineralization were consistent with ob served data. The modeled estimates for soil carbon were consistent wit h those from regional-scale empirical regression models. High correlat ion (R-2 = 0.92) with data was obtained for the simulation of soil car bon dynamics of the boreal forest, but the model overestimated soil ca rbon (0-20 cm) by 2-8% for fine-textured soil and underestimated soil carbon by 5-18% for sandy soil. The effects of climatic variation on t emporal changes in biomass and soil carbon storage over the past centu ry were found to be very different for southern and northern sites but relatively insensitive to site-specific soil texture. The main discre pancies between observed data and CENTURY 4.0 results are associated w ith the effects of soil texture and an inadequate representation of fi re disturbance on C dynamics of boreal forests. Further improvements, particularly in the representation of disturbance regimes and in the s imulation of slow pool C dynamics, are suggested to enhance its predic tive capability.