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 N-saturated 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.