Modeling potentially sustainable biomass productivity in jack pine forest stands

A steady-state mass balance model (ForSust), developed to simulate potentially sustainable levels of tree biomass growth and related nutrient uptake dynamics, was applied to 17 jack pine sites across Canada. The model simulates potential tree biomass growth based on nutrient inputs from estimated atmospheric deposition (N, Ca, Mg, K) and soil weathering (Ca, Mg, K), and matches the resulting nutrient supply rates with calculated nutrient demand. Nutrient demand calculations are based on nutrient concentrations in wood, bark, branches, and foliage. Specifically, the model simulates sustainable annual increment (SAI) of biomass growth for stem-only and whole-tree (aboveground biomass) harvesting, and for recurring forest fire conditions. Calculated SAI levels were compared with field-estimated mean annual increments for aboveground forest biomass (MAI). For recurring forest fires, it was found that SAI values, as simulated, corresponded with the MAI field estimates in general. For whole-tree harvesting, SAI was lower than MAI for most but not all sites. For stem-only harvesting, SAI corresponded with MAI, but there was a greater scatter between SAI and MAI values than what appeared to be the case for the recurring forest fire scenario. Key words: Jack pine; whole-tree, stem-only harvesting; steady-state mass balance; forest biomass; N, Ca, Mg, K growth limitations; atmospheric deposition