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 adaptat ions concern the simulation of seed regeneration of subarctic forest c ommunities growing on moderately to well drained sites. The yearly see d production in Picea mariana (Mill.) B.S.P. stands is controlled by t emperature and stand structural characteristics. In addition to the se ed input, the model considers the influence of seedbed properties on t he establishment of seedlings. Overall, this model simulates the entir e regeneration dynamics in a more realistic way than in most other gap models where successional processes are driven by resource constraint s on tree growth. The model produces realistic predictions about the p attern of early post-fire age structure, and the biomas and density dy namics of black spruce populations. Simulations under a climate-warmin g scenario suggest that physiognomic change in subarctic spruce-lichen woodland would be more pronounced in areas subjected to moderately fr equent forest fires than in those where the fire frequency is very low .