Evaluation of 11 terrestrial carbon-nitrogen cycle models against observations from two temperate Free-Air CO 2 Enrichment studies


Journal Article

We analysed the responses of 11 ecosystem models to elevated atmospheric [CO 2 ] (eCO 2 ) at two temperate forest ecosystems (Duke and Oak Ridge National Laboratory (ORNL) Free-Air CO 2 Enrichment (FACE) experiments) to test alternative representations of carbon (C)-nitrogen (N) cycle processes. We decomposed the model responses into component processes affecting the response to eCO 2 and confronted these with observations from the FACE experiments. Most of the models reproduced the observed initial enhancement of net primary production (NPP) at both sites, but none was able to simulate both the sustained 10-yr enhancement at Duke and the declining response at ORNL: models generally showed signs of progressive N limitation as a result of lower than observed plant N uptake. Nonetheless, many models showed qualitative agreement with observed component processes. The results suggest that improved representation of above-ground-below-ground interactions and better constraints on plant stoichiometry are important for a predictive understanding of eCO 2 effects. Improved accuracy of soil organic matter inventories is pivotal to reduce uncertainty in the observed C-N budgets. The two FACE experiments are insufficient to fully constrain terrestrial responses to eCO 2 , given the complexity of factors leading to the observed diverging trends, and the consequential inability of the models to explain these trends. Nevertheless, the ecosystem models were able to capture important features of the experiments, lending some support to their projections. © 2014 New Phytologist Trust.

Full Text

Duke Authors

Cited Authors

  • Zaehle, S; Medlyn, BE; De Kauwe, MG; Walker, AP; Dietze, MC; Hickler, T; Luo, Y; Wang, YP; El-Masri, B; Thornton, P; Jain, A; Wang, S; Warlind, D; Weng, E; Parton, W; Iversen, CM; Gallet-Budynek, A; Mccarthy, H; Finzi, A; Hanson, PJ; Prentice, IC; Oren, R; Norby, RJ

Published Date

  • January 1, 2014

Published In

Volume / Issue

  • 202 / 3

Start / End Page

  • 803 - 822

Electronic International Standard Serial Number (EISSN)

  • 1469-8137

International Standard Serial Number (ISSN)

  • 0028-646X

Digital Object Identifier (DOI)

  • 10.1111/nph.12697

Citation Source

  • Scopus