Articles | Volume 8, issue 7
Geosci. Model Dev., 8, 2035–2065, 2015
Geosci. Model Dev., 8, 2035–2065, 2015

Development and technical paper 13 Jul 2015

Development and technical paper | 13 Jul 2015

A vertically discretised canopy description for ORCHIDEE (SVN r2290) and the modifications to the energy, water and carbon fluxes

K. Naudts1,14, J. Ryder1, M. J. McGrath1, J. Otto1,10, Y. Chen1, A. Valade1, V. Bellasen2, G. Berhongaray3, G. Bönisch4, M. Campioli3, J. Ghattas1, T. De Groote3,11, V. Haverd5, J. Kattge4, N. MacBean1, F. Maignan1, P. Merilä6, J. Penuelas7,12, P. Peylin1, B. Pinty8, H. Pretzsch9, E. D. Schulze4, D. Solyga1,13, N. Vuichard1, Y. Yan3, and S. Luyssaert1 K. Naudts et al.
  • 1LSCE, IPSL, CEA-CNRS-UVSQ, 91191 Gif-sur-Yvette, France
  • 2INRA, 21079 Dijon, France
  • 3University of Antwerp, 2610 Wilrijk, Belgium
  • 4MPI-Biogeochemistry, Jena, Germany
  • 5CSIRO-Ocean and Atmosphere Flagship, 2600 Canberra, Australia
  • 6METLA, Oulu, Finland
  • 7CSIC, Global Ecology Unit CREAF-CSIC-UAB, Cerdanyola del Valles, Spain
  • 8European Commission, Joint Research Centre, Ispra, Italy
  • 9TUM, Munich, Germany
  • 10Helmholtz-Zentrum Geesthacht, Climate Service Center 2.0, Hamburg, Germany
  • 11VITO, 2400 Mol, Belgium
  • 12CREAF, Cerdanyola del Vallès, Spain
  • 13CGG, 91341 Massy, France
  • 14MPI-Meteorology, Hamburg, Germany

Abstract. Since 70 % of global forests are managed and forests impact the global carbon cycle and the energy exchange with the overlying atmosphere, forest management has the potential to mitigate climate change. Yet, none of the land-surface models used in Earth system models, and therefore none of today's predictions of future climate, accounts for the interactions between climate and forest management. We addressed this gap in modelling capability by developing and parametrising a version of the ORCHIDEE land-surface model to simulate the biogeochemical and biophysical effects of forest management. The most significant changes between the new branch called ORCHIDEE-CAN (SVN r2290) and the trunk version of ORCHIDEE (SVN r2243) are the allometric-based allocation of carbon to leaf, root, wood, fruit and reserve pools; the transmittance, absorbance and reflectance of radiation within the canopy; and the vertical discretisation of the energy budget calculations. In addition, conceptual changes were introduced towards a better process representation for the interaction of radiation with snow, the hydraulic architecture of plants, the representation of forest management and a numerical solution for the photosynthesis formalism of Farquhar, von Caemmerer and Berry. For consistency reasons, these changes were extensively linked throughout the code. Parametrisation was revisited after introducing 12 new parameter sets that represent specific tree species or genera rather than a group of often distantly related or even unrelated species, as is the case in widely used plant functional types. Performance of the new model was compared against the trunk and validated against independent spatially explicit data for basal area, tree height, canopy structure, gross primary production (GPP), albedo and evapotranspiration over Europe. For all tested variables, ORCHIDEE-CAN outperformed the trunk regarding its ability to reproduce large-scale spatial patterns as well as their inter-annual variability over Europe. Depending on the data stream, ORCHIDEE-CAN had a 67 to 92 % chance to reproduce the spatial and temporal variability of the validation data.

Short summary
Despite the potential of forest management to mitigate climate change, none of today's predictions of future climate accounts for the impact of forest management. To address this gap in modelling capability, we developed and parametrised a land-surface model to simulate biogeochemical and biophysical effects of forest management. Comparison of model output against data showed an increased model performance in reproducing large-scale spatial patterns and inter-annual variability over Europe.