FACE Model-Data Synthesis
Plant photosynthetic rates increase and stomatal apertures decrease in response to elevated atmospheric CO2 (eCO2), increasing both plant carbon (C) availability and water use efficiency. These physiological responses to eCO2 are well characterised and understood, however the ecological effects of these responses as they cascade through plant and ecosystem processes are complex and subject to multiple interactions and feedbacks that operate at various timescales. Therefore the response of the terrestrial carbon sink to increasing atmospheric CO2 remains the largest uncertainty in global C cycle modelling to date, and is a huge contributor to uncertainty in projections of climate change.
The Free Air CO2 Enrichment Model-Data Synthesis (FACE-MDS) was established in 2008 with support from the National Center for Ecological Analysis and Synthesis and from 2011 onwards with funding from the Biological and Environmental Research program of DOE's Office of Science. The initial plan was to benchmark model predictions of terrestrial ecosystem responses to elevated atmospheric CO2 using data from the Duke and Oak Ridge FACE experiments, two of the longest and most comprehensive experimental datasets on ecosystem responses to elevated CO2. The project soon evolved to delve deeper into model results and pull apart the underlying reasons for model behaviour, a method we refer to as model-data synthesis or assumption centered modeling. The FACE-MDS working group has advanced understanding of terrestrial ecosystem responses to elevated atmospheric CO2, identified areas for model improvements and questions for further experimental analysis, and advances a new standard for model intercomparison which we hope will be adopted by many modeling groups.
The FACE-MDS is a national and international collaboration of scientists at 20 institutions across six nations led by principal investigators at Oak Ridge National Laboratory in the USA and key partners at Hawkesbury Institute for Environment and Macquarie University in Australia, and Max Planck Institute for Biogeochemistry in Germany. The distribution of key partners and collaborators across the globe posed an interesting challenge to the organization of the project. Communication was primarily via annual project meetings and direct emails.
We would like to thank our DOE and NCEAS sponsors for their support and all our collaborators for many unfunded hours donated to the project.
If you have any questions please contact Anthony Walker (walkerap _at_ ornl.gov) or Rich Norby (norbyrj _at_ ornl.gov).
Sánchez-de León, Y., Wise, D.H., Lugo-Pérez, J., Norby, R.J., James, S.W., Gonzalez-Meler, M.A., 2018. Endogeic earthworm densities increase in response to higher fine-root production in a forest exposed to elevated CO2. Soil Biology and Biochemistry 122, 31-38 doi:10.1016/j.soilbio.2018.03.027. [pdf]
Ryan, E.M., Ogle, K., Peltier, D., Walker, A.P., De Kauwe, M.G., Medlyn, B.E., Williams, D.G., Parton, W., Asao, S., Guenet, B., Harper, A.B., Lu, X., Luus, K.A., Zaehle, S., Shu, S., Werner, C., Xia, J., Pendall, E., 2017. Gross primary production responses to warming, elevated CO2, and irrigation: quantifying the drivers of ecosystem physiology in a semiarid grassland. Glob Change Biology 23, 3092–3106. doi:10.1111/gcb.13602. [pdf]
De Kauwe, M.G., Medlyn, B.E., Walker, A.P., Zaehle, S., Asao, S., Guenet, B., Harper, A.B., Hickler, T., Jain, A., Luo, Y., Lu, X., Luus, K., Parton, W.J., Shu, S., Wang, Y.-P., Werner, C., Xia, J., Pendall, E., Morgan, J.A., Ryan, E.M., Carrillo, Y., Dijkstra, F.A., Zelikova, T.J., Norby, R.J., 2017. Challenging terrestrial biosphere models with data from the long-term multi-factor Prairie Heating and CO2 Enrichment experiment. Glob Change Biology 23, 3623-3645 doi:10.1111/gcb.13643. [pdf]
Norby, R.J., Kauwe, M.G.D., Walker, A.P., Werner, C., Zaehle, S., Zak, D.R., 2017. Comment on “Mycorrhizal association as a primary control of the CO2 fertilization effect.” Science 355, 358–358. doi:10.1126/science.aai7976. [pdf]
Norby, R.J., De Kauwe, M.G., Domingues, T.F., Duursma, R.A., Ellsworth, D.S., Goll, D.S., Lapola, D.M., Luus, K.A., MacKenzie, A.R., Medlyn, B.E., Pavlick, R., Rammig, A., Smith, B., Thomas, R., Thonicke, K., Walker, A.P., Yang, X., Zaehle, S., 2016. Model-data synthesis for the next generation of forest free-air CO2 enrichment (FACE) experiments. New Phytologist 209, 17–28. doi:10.1111/nph.13593. [pdf]
Medlyn, B.E., Zaehle, S., De Kauwe, M.G., Walker, A.P., Dietze, M.C., Hanson, P.J., Hickler, T., Jain, A.K., Luo, Y., Parton, W.J., Prentice, I.C., Thornton, P.E., Wang, S., Wang, Y.-P., Weng, E., Iversen, C.M., McCarthy, H.R., Warren, J.M., Oren, R., Norby, R.J., 2015. Using ecosystem experiments to improve vegetation models Nature Climate Change 5, 528–534. doi:10.1038/nclimate2621. [pdf]
Walker, A.P., Zaehle, S., Medlyn, B.E., De Kauwe, M.G., Asao, S., Hickler, T., Parton, W., Ricciuto, D., Wang, Y.-P., Wårlind, D., Norby, R.J., 2015. Predicting long-term carbon sequestration in response to CO2 enrichment: How and why do current ecosystem models differ? Global Biogeochemical Cycles 2014GB004995. doi:10.1002/2014GB004995 [pdf]
De Kauwe, M.G., Medlyn, B.E., Zaehle, S., Walker, A.P., Dietze, M.C., Wang, Y.-P., Luo, Y., Jain, A.K., El-Masri, B., Hickler, T., Wårlind, D., Weng, E., Parton, W.J., Thornton, P.E., Wang, S., Prentice, I.C., Asao, S., Smith, B., McCarthy, H.R., Iversen, C.M., Hanson, P.J., Warren, J.M., Oren, R., Norby, R.J., 2014. Where does the carbon go? A model–data intercomparison of vegetation carbon allocation and turnover processes at two temperate forest free-air CO2 enrichment sites. New Phytologist 203, 883–899. doi:10.1111/nph.12847. [pdf]
Walker, A.P., Hanson, P.J., De Kauwe, M.G., Medlyn, B.E., Zaehle, S., Asao, S., Dietze, M., Hickler, T., Huntingford, C., Iversen, C.M., Jain, A., Lomas, M., Luo, Y., Mccarthy, H., Parton, W.J., Prentice, I.C., Thornton, P.E., Wang, S., Wang, Y.-P., Wårlind, D., Weng, E., Warren, J.M., Woodward, F.I., Oren, R., Norby, R.J., 2014. Comprehensive ecosystem model-data synthesis using multiple data sets at two temperate forest free-air CO2 enrichment experiments: Model performance at ambient CO2 concentration. J. Geophysical Research Biogeosciences 119, 2013JG002553. doi:10.1002/2013JG002553. [pdf]
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., Wårlind, D., Weng, E., Parton, W., Iversen, C.M., Gallet-Budynek, A., Mccarthy, H., Finzi, A., Hanson, P.J., Prentice, I.C., Oren, R., 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. doi:10.1111/nph.12697. [pdf]
De Kauwe, M.G., Medlyn, B.E., Zaehle, S., Walker, A.P., Dietze, M.C., Hickler, T., Jain, A.K., Luo, Y., Parton, W.J., Prentice, I.C., Smith, B., Thornton, P.E., Wang, S., Wang, Y.-P., Wårlind, D., Weng, E., Crous, K.Y., Ellsworth, D.S., Hanson, P.J., Seok Kim, H.-, Warren, J.M., Oren, R., Norby, R.J., 2013. Forest water use and water use efficiency at elevated CO2: a model-data intercomparison at two contrasting temperate forest FACE sites. Global Change Biology 19, 1759–1779. doi:10.1111/gcb.12164. [pdf]