Photosynthetic parameters are key for predicting the carbon cycle and fluxes in terrestrial ecosystems. In northern high-latitude regions where cold temperatures limit available nitrogen for plants, the photosynthetic parameters are tightly linked with the nitrogen content. Here, we present the leaf- and ecosystem-scale photosynthetic parameters, the maximum carboxylation rate (vcmax25), based on leaf chamber measurements and eddy covariance data from two mature black spruce forests and one young aspen-birth forest in interior Alaska. The leaf carbon to nitrogen ratio (C:N ratio) explained most of the variations in vcmax25 across the five vascular plants (Picea mariana, Betula glandulosa, Ledum groenlandicum, Betula papyrifera, and Populus tremuloides)(R2 = 0.68; p < 0.01), including the overstory and understory, from the three forests. Each plant had a small within-species variability of vcmax25 and leaf C:N, suggesting that plants have a specific potential for available N in photosynthesis. This result indicates that the canopy structure and community composition are presumably important factors for modeling the canopy photosynthesis across boreal forests in interior Alaska. The ecosystem-scale vcmax25 determined from the eddy covariance data further supported this hypothesis.