Working group: G. Berthier, P. Ciais, J. Ghattas, F. Maignan, S. Peng, P. Peylin, N. Viovy

Two recent MIPs (MsTMIP and TRENDY2) have evidenced two defaults in ORCHIDEE:

• a too large GPP at global scale,
• a too large response to CO2 increasing atmospheric concentrations.

For the first part S. Peng has demonstrated that the problem was mainly in the Tropics. Based on publications he proposed the modifications of several parameters for tropical forests (PFT 2 and 3):

• allocation to stem fraction (Malhi et al., 2011),
• maintenance respiration (Piao et al., 2010 ; Malhi et al., 2011 ; Verbeeck et al., 2011 ; Kuppel et al., 2012),
• coefficients of biomass export (Earles at al., 2012).

For the second part, P. Ciais proposed to add a CO2 down-regulation process (Sellers et al., 1996 ; Bounoua et al., 1999, 2010). It was implemented in diffuco_trans_co2 in the following manner:

      IF (downregulation_co2) THEN
         vcmax(:,jv) = assim_param(:,jv,ivcmax)*(un-downregulation_co2_coeff(jv)*log(ccanopy(:)/downregulation_co2_baselevel))	
         vjmax(:,jv) = assim_param(:,jv,ivjmax)*(un-downregulation_co2_coeff(jv)*log(ccanopy(:)/downregulation_co2_baselevel))	
      ELSE
         vcmax(:,jv) = assim_param(:,jv,ivcmax)
         vjmax(:,jv) = assim_param(:,jv,ivjmax)
      ENDIF	

Tests were done for MsTMIP and TRENDY-2 at a coarse 2° spatial resolution:

Considering these results, it was decided to commit these changes, they were done in revision [1882].

References:
All references are available on the Cloud.

• Bounoua, L., Collatz, G. J., Sellers, P. J., Randall, D. A., Dazlich, D. A., Los, S. O., Berry, J. A., Fung, I., Tucker, C. J., Field, C. B., and Jensen, T. G.: Interactions between vegetation and climate: Radiative and physiological effects of doubled atmospheric co2, Journal of Climate, 12, 309-324, Doi 10.1175/1520-0442(1999)012<0309:Ibvacr>2.0.Co;2, 1999.
• Bounoua, L., Hall, F. G., Sellers, P. J., Kumar, A., Collatz, G. J., Tucker, C. J., and Imhoff, M. L.: Quantifying the negative feedback of vegetation to greenhouse warming: A modeling approach, Geophysical Research Letters, 37, Artn L23701, Doi 10.1029/2010gl045338, 2010.
• Earles, J. M., Yeh, S., and Skog, K. E.: Timing of carbon emissions from global forest clearance, Nature Climate Change, 2, 682-685, Doi 10.1038/Nclimate1535, 2012.
• Kattge, J., Knorr, W., Raddatz, T., and Wirth, C.: Quantifying photosynthetic capacity and its relationship to leaf nitrogen content for global-scale terrestrial biosphere models, Global Change Biology, 15, 976-991, DOI 10.1111/j.1365-2486.2008.01744.x, 2009.
• Kuppel, S., Peylin, P., Chevallier, F., Bacour, C., Maignan, F., and Richardson, A. D.: Constraining a global ecosystem model with multi-site eddy-covariance data, Biogeosciences, 9, 3757-3776, DOI 10.5194/bg-9-3757-2012, 2012.
• Lewis, J. D., Ward, J. K., and Tissue, D. T.: Phosphorus supply drives nonlinear responses of cottonwood (populus deltoides) to increases in co2 concentration from glacial to future concentrations, New Phytologist, 187, 438-448, DOI 10.1111/j.1469-8137.2010.03307.x, 2010.
• Malhi, Y., Doughty, C., and Galbraith, D.: The allocation of ecosystem net primary productivity in tropical forests, Philosophical Transactions of the Royal Society B-Biological Sciences, 366, 3225-3245, DOI 10.1098/rstb.2011.0062, 2011.
• Piao, S. L., Luyssaert, S., Ciais, P., Janssens, I. A., Chen, A. P., Cao, C., Fang, J. Y., Friedlingstein, P., Luo, Y. Q., and Wang, S. P.: Forest annual carbon cost: A global-scale analysis of autotrophic respiration, Ecology, 91, 652-661, Doi 10.1890/08-2176.1, 2010.
• Sellers, P. J., Bounoua, L., Collatz, G. J., Randall, D. A., Dazlich, D. A., Los, S. O., Berry, J. A., Fung, I., Tucker, C. J., Field, C. B., and Jensen, T. G.: Comparison of radiative and physiological effects of doubled atmospheric co2 on climate, Science, 271, 1402-1406, DOI 10.1126/science.271.5254.1402, 1996.
• Verbeeck, H., Peylin, P., Bacour, C., Bonal, D., Steppe, K., and Ciais, P.: Seasonal patterns of co2 fluxes in amazon forests: Fusion of eddy covariance data and the orchidee model, Journal of Geophysical Research-Biogeosciences, 116, Artn G02018, Doi 10.1029/2010jg001544, 2011.