A new paper came out in this month’s issue of the journal Global Change Biology. An increasing number of global models that include a representation of how nitrogen limits production of carbon and biomass in forests, grasslands, and crops are being used to predict global climate and help inform climate policy. We evaluated how well two widely-used global models with carbon and nitrogen cycles represent nitrogen limitation by comparing model simulations to data from forests and grasslands. The model response to simulated nitrogen fertilization differed drastically between models but the average of the two models compared well to observations. In the paper we explore why they are different and how to potentially advance the models. This was the first study to systematically evaluate multiple global models that include the nitrogen cycle and will hopefully help guide the improvement of models and collection of additional observational data.
Thomas, R. Q., S. Zaehle, P.H. Templer, and C.L. Goodale. Global patterns of nitrogen limitation: Confronting two global biogeochemical models with observations. Global Change Biology 19, 2986–2998