Carbon and nitrogen cycling in North American boreal forests. II. Biogeographic patterns

A model of carbon and nitrogen cycling developed with ecological relationships from upland boreal forests in interior Alaska was tested with forest structure and forest floor data from several bioclimatic regions of the North American boreal forest. Test forests included black spruce (Piceamariana (Mill.) B.S.P.), white spruce (Piceaglauca (Moench) Voss), white birch (Betulapapyrifera Marsh.), balsam fir (Abiesbalsamea (L.) Mill.), and jack pine (Pinusbanksiana Lamb.) stands located in five different bioclimatic regions. Test comparisons of simulated and actual data included aboveground tree biomass, basal area, density, litter fall, and moss and lichen biomass as well as forest floor biomass, turnover, thickness, nitrogen concentration, and nitrogen mineralization. The model correctly simulated 60 (76%) of the 79 variables tested. Approximately 42% of the incorrectly simulated variables occurred in one forest. The major recurring errors included inaccurate moss and lichen biomass and low moss nitrogen concentrations. These tests indicated that ecological relationships from interior Alaska can be extended to other boreal forest regions and identified the factors controlling vegetation patterns in different bioclimatic regions of the North American boreal forest.