SIMULATION OF MIXEDWOOD MANAGEMENT OF ASPEN AND WHITE SPRUCE IN NORTHEASTERN BRITISH-COLUMBIA

FORECAST, an ecosystem simulation model, was calibrated for aspen (Pop ulus tremuloides Michx) and white spruce (Picea glauca (Moench) Voss) stands using data collected in the Boreal White and Black Spruce bioge oclimatic zone in northeastern British Columbia and published data. Si mulations were undertaken to examine the effects of initial density of aspen on yield of white spruce in an aspen and spruce mixedwood stand , and to compare the predicted stemwood biomass yields of aspen, white spruce and mixedwood stands. Results of the simulations suggest that mixedwood management regimes on the same medium quality site should ha ve higher stemwood yield compared to pure white spruce stand. Simulate d stemwood biomass yield of pure aspen stands over 240 years on medium site varied from 682.5 Mg ha(-1) to 239.1 Mg ha(-1) for different rot ation lengths (30 to 120 years). Repeated rotations of monoculture whi te spruce produced much less stemwood biomass, simulated yields over 2 40 years ranging from 877.3 Mg ha(-1) to 248.4 Mg ha(-1) for rotation lengths of 60 to 240 years. Simulated aspen and white spruce mixedwood stands produced higher stemwood biomass yields than the pure white sp ruce stands, but less than the pure aspen stands; from 217.4 Mg ha(-1) to 292.8 Mg ha(-1) over 240 years. Variations in initial densities of aspen did not affect spruce stemwood biomass yield over the simulatio n period. This model shows potential for comparing the relative effect s of different management strategies on harvestable volume and variety of other ecosystem variables. A calibrated version of the model shoul d be useful as both a management simulator and a research tool. Howeve r, shortcomings in the representation of the canopy architecture of mi xed species stands suggested the need to develop an individual tree ve rsion of this ecosystem management model for application to mixed spec ies stands.