Carbon-Nitrogen Cycle Models of Forest Responses to Elevated CO2
Zaehle, S., Medlyn, B.E., De Kauwe, M.G., Walker, A.P., Dietze, M.C., Hickler, T., Luo, Y., Wang, Y.-P., El-Masri, B., Thornton, P., Jain, A., Wang, S., Warlind, D., Weng, E., Parton, W., Iversen, C.M., Gallet-Budynek, A., McCarthy, H., Finzi, A., Hanson, P.J., Prentice, I.C., Oren, R. and Norby, R.J. 2014. Evaluation of 11 terrestrial carbon-nitrogen cycle models against observations from two temperate Free-Air CO2 Enrichment studies. New Phytologist 202: 803-822.
Because of the fact that "most models failed to simulate the sustained NPP enhancement at the Duke FACE site," the 23 researchers - hailing from 7 different countries - conclude "this tendency to underestimate the net transfer of N from soils to vegetation under elevated CO2 at Duke calls for a better representation of below-ground processes, in particular root allocation and microbial responses to enhanced rhizodeposition." We could not agree more; for something has clearly overpowered the Progressive Nitrogen Limitation Hypothesis in this and many other such studies, as is indicated in the reviews of numerous other analyses of the hypothesis that we have archived under this heading.
McCarthy, H,.R., Oren, R., Johnsen, K.H., Gallet-Budynek, A., Pritchard, S.G., Cook, C.W., LaDeau, S.L., Jackson, R.B. and Finzi, A.C. 2010. Re-assessment of plant carbon dynamics at the Duke free-air CO2 enrichment site: interactions of atmospheric [CO2] with nitrogen and water availability over stand development. New Phytologist 185: 514-528.
Norby, R.J., Warren, J.M., Iversen, C.M., Medlyn, B.E. and McMurtrie, R.E. 2010. CO2 enhancement of forest productivity constrained by limited nitrogen availability. Proceedings of the National Academy of Sciences, USA 107: 19,368-19,373.