Estimating net primary production of forests in the Canadian Prairie Provinces using an inventory-based carbon budget model

The Carbon Budget Model of the Canadian Forest Sector (CBM-CFS2) is a forest inventory-based ecosystem simulation model. It has been used previously for both retrospective and projective analyses of the carbon pools and fluxes of the Canadian forest ecosystems at the national, regional, and stand level. The objective of this study was to determine and evaluate forest net primary production (NPP) in the three Prairie Provinces in west-central Canada, as estimated by the model. The model simulated an averaged aboveground NPP (NPP(A)) of 172 g C(.)m-2(.)year-1 for the regional forests, varying from 72 to 293 g C(.)m-2(.)year-1, depending on ecoclimatic province, forest type, age, and site productivity. Comparisons of NPP(A) estimates for the boreal forest (165-179 g C(.)m-2(.)year-1) with results from direct measurements, modeling, and empirical calculations show that the CBM-CFS2 produced reasonable estimates of NPP(A). The model incorporates different types of disturbances such as wildfire, harvesting, and insects and is able to evaluate NPP changes with stand age. However, belowground NPP may be overestimated, especially for young and unproductive stands. This can be explained by the current parameter estimates for the fine-root component of belowground biomass and for fine-root turnover rates.