A modified nitrogen budget for temperate deciduous forests in an advanced stage of nitrogen saturation

[1] Recent advances in ecosystem descriptions associated with nitrogen (N) saturated forests allowed us to revise and improve a model of ecosystem productivity to reflect advanced N saturation. We introduce a new description of nitrogen cycling for a forest that is in stage 2 of N saturation on the basis of recent literature. We compared the accuracy of this new description to the conventional N cycling construct by assessing the degree to which each N cycle description predicted observations in a 100-year-old Nsaturated watershed in the Fernow Experimental Forest. The new literature-based model of saturation outperformed the original model by more accurately predicting aboveground net primary productivity, foliar N, and stream NO3 . Regional estimates of forest productivity and terrestrial carbon sequestration have generally overlooked variable N availability as a vector for forest growth changes. New findings about N-saturated ecosystem processes refine productivity models and improve estimates of regional ecosystem changes in response to N saturation.