DEVELOPMENT OF A SIMULATION-MODEL OF THE FOREST TUNDRA TRANSITION ZONE OF NORTHEASTERN CANADA

A forest succession model has been adapted to simulate the dynamics of subarctic spruce-lichen woodland of northeastern Canada. Most adaptations concern the simulation of seed regeneration of subarctic forest communities growing on moderately to well drained sites. The yearly seed production in Picea mariana (Mill.) B.S.P. stands is controlled by temperature and stand structural characteristics. In addition to the seed input, the model considers the influence of seedbed properties on the establishment of seedlings. Overall, this model simulates the entire regeneration dynamics in a more realistic way than in most other gap models where successional processes are driven by resource constraints on tree growth. The model produces realistic predictions about the pattern of early post-fire age structure, and the biomas and density dynamics of black spruce populations. Simulations under a climate-warming scenario suggest that physiognomic change in subarctic spruce-lichen woodland would be more pronounced in areas subjected to moderately frequent forest fires than in those where the fire frequency is very low.