title: Challenging terrestrial biosphere models with data from the long-term multifactor Prairie Heating and CO2Enrichment experiment.
abstract: Multifactor experiments are often advocated as important for advancing terrestrial biosphere models (TBMs), yet to date, such models have only been tested against single-factor experiments. We applied 10 TBMs to the multifactor Prairie Heating and CO2Enrichment (PHACE) experiment in Wyoming, USA. Our goals were to investigate how multifactor experiments can be used to constrain models and to identify a road map for model improvement. We found models performed poorly in ambient conditions; there was a wide spread in simulated above-ground net primary productivity (range: 31-390 g C m-2yr-1). Comparison with data highlighted model failures particularly with respect to carbon allocation, phenology, and the impact of water stress on phenology. Performance against the observations from single-factors treatments was also relatively poor. In addition, similar responses were predicted for different reasons across models: there were large differences among models in sensitivity to water stress and, among the N cycle models, N availability during the experiment. Models were also unable to capture observed treatment effects on phenology: they overestimated the effect of warming on leaf onset and did not allow CO2-induced water savings to extend the growing season length. Observed interactive (CO2× warming) treatment effects were subtle and contingent on water stress, phenology, and species composition. As the models did not correctly represent these processes under ambient and single-factor conditions, little extra information was gained by comparing model predictions against interactive responses. We outline a series of key areas in which this and future experiments could be used to improve model predictions of grassland responses to global change.
authors.affiliation: Department of Biological Science, Macquarie University, North Ryde, NSW, 2109, Australia.
authors.forename: Martin G
authors.identifier: 0000-0002-3399-9098
authors.initials: MG
authors.lastname: De Kauwe
authors.affiliation: Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia.
authors.forename: Belinda E
authors.identifier: 0000-0001-5728-9827
authors.initials: BE
authors.lastname: Medlyn
authors.affiliation: Environmental Sciences Division and Climate Change Science Institute, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN, 37831, USA.
authors.forename: Anthony P
authors.initials: AP
authors.lastname: Walker
authors.affiliation: Biogeochemical Integration Department, Max Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, 07745, Jena, Germany.
authors.forename: Sönke
authors.initials: S
authors.lastname: Zaehle
authors.affiliation: Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, CO, 80523-1499, USA.
authors.forename: Shinichi
authors.initials: S
authors.lastname: Asao
authors.affiliation: Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, F-91191, Gif-sur-Yvette, France.
authors.forename: Bertrand
authors.initials: B
authors.lastname: Guenet
authors.affiliation: College of Engineering, Mathematics, and Physical Sciences, University of Exeter, Exeter, EX4 4QF, UK.
authors.forename: Anna B
authors.initials: AB
authors.lastname: Harper
authors.affiliation: Senckenberg Biodiversity and Climate Research Centre (BiK-F), Senckenberganlage 25, 60325, Frankfurt, Germany.|Department of Physical Geography, Geosciences, Goethe-University, Altenhöferallee 1, 60438, Frankfurt, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Hickler
authors.affiliation: Department of Atmospheric Sciences, University of Illinois, 105 South Gregory Street, Urbana, IL, 61801-3070, USA.
authors.forename: Atul K
authors.initials: AK
authors.lastname: Jain
authors.affiliation: Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK, 73019, USA.
authors.forename: Yiqi
authors.initials: Y
authors.lastname: Luo
authors.affiliation: CSIRO Oceans and Atmosphere, Private Bag #1, Aspendale, Vic., 3195, Australia.
authors.forename: Xingjie
authors.initials: X
authors.lastname: Lu
authors.affiliation: Biogeochemical Integration Department, Max Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, 07745, Jena, Germany.
authors.forename: Kristina
authors.initials: K
authors.lastname: Luus
authors.affiliation: Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, CO, 80523-1499, USA.
authors.forename: William J
authors.initials: WJ
authors.lastname: Parton
authors.affiliation: Department of Atmospheric Sciences, University of Illinois, 105 South Gregory Street, Urbana, IL, 61801-3070, USA.
authors.forename: Shijie
authors.initials: S
authors.lastname: Shu
authors.affiliation: CSIRO Oceans and Atmosphere, Private Bag #1, Aspendale, Vic., 3195, Australia.
authors.forename: Ying-Ping
authors.initials: YP
authors.lastname: Wang
authors.affiliation: Senckenberg Biodiversity and Climate Research Centre (BiK-F), Senckenberganlage 25, 60325, Frankfurt, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Werner
authors.affiliation: Tiantong National Forest Ecosystem Observation and Research Station, School of Ecological and Environmental Sciences, East China Normal University, Shanghai, 200062, China.
authors.forename: Jianyang
authors.initials: J
authors.lastname: Xia
authors.affiliation: Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia.
authors.forename: Elise
authors.initials: E
authors.lastname: Pendall
authors.affiliation: Rangeland Resources Research Unit, Agricultural Research Service, United States Department of Agriculture, Fort Collins, CO, 80526, USA.
authors.forename: Jack A
authors.initials: JA
authors.lastname: Morgan
authors.affiliation: Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YW, UK.
authors.forename: Edmund M
authors.identifier: 0000-0002-7003-9707
authors.initials: EM
authors.lastname: Ryan
authors.affiliation: Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia.
authors.forename: Yolima
authors.initials: Y
authors.lastname: Carrillo
authors.affiliation: Centre for Carbon, Water and Food, School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW, 2006, Australia.
authors.forename: Feike A
authors.initials: FA
authors.lastname: Dijkstra
authors.affiliation: Department of Botany, University of Wyoming, Laramie, WY, 82071, USA.
authors.forename: Tamara J
authors.initials: TJ
authors.lastname: Zelikova
authors.affiliation: Environmental Sciences Division and Climate Change Science Institute, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN, 37831, USA.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Norby
mesh_terms: D002245:Carbon Dioxide; D065948:Grassland; D006361:Heating; D006109:Poaceae / Q000254:growth & development*; D012987:Soil; D014959:Wyoming
chemical_list: D012987:Soil; D002245:Carbon Dioxide
keywords: 
  FACE
  ; 
  PHACE
  ; allocation; carbon dioxide; grassland; models; phenology; soil moisture; temperature