Development and application of an upland boreal forest succession model

A mathematical model was developed to simulate forest succession on permafrost and permafrost-free sites for upland sites near Fairbanks, Alaska. Monthly precipitation and ambient air temperature were generated based on long term records. Site-specific incident sunlight was calculated for given aspects and slopes. Soil moisture regimes were estimated monthly based on precipitation and evapotranspiration. Soil thermal regimes were calculated according to available sunlight and net freezing or thawing ambient air temperatures through time. Individual tree growth was estimated annually for all individuals on a plot, modified according to species-specific growth attributes, competitive factors and climatic characteristics. The model successfully simulated the successional patterns of species dominance on both permafrost and non-permafrost sites. Results indicated that species composition and successional dominance on permafrost sites were greatly influenced by species' sensitivities to active layer depth.