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Vuichard

Timestamp:: 2014-03-17T15:42:45+01:00 (10 years ago)
Author:: nvuilsce
Comment:: --

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DevelopmentActivities/MergeOCN/Vuichard

-                      v75
+                      v76
 In both schemes, the impact of the leaf N on the photosynthesis is accounted for, but in different manner.
 * In diffuco_trans_cexchange, the impact of leaf N on photosynthesis is based on the former work of Friend (2001, appendix 2, [https://cloud.lsce.ipsl.fr/index.php/apps/files/download/Shared/ORCHIDEE/REFERENCES/ORCHIDEE-N/Friend_2001.pdf here]) that is itself based on the work of Kull and Kruijt (1998, [https://cloud.lsce.ipsl.fr/index.php/apps/files/download/Shared/ORCHIDEE/REFERENCES/ORCHIDEE-N/kull_1998.pdf here]).[[BR]]In this scheme, one assume that the leaf N is impacting Vmax, Jmax and the effective quantum efficiency of the leaf for CO2 uptake (the alpha parameter). The former impact is directly related to the concentration in Chlorophyl which is function of the N concentration (see below).[[BR]] As in Friend and Kiang (2005, eq. 2 and paragraph above, [https://cloud.lsce.ipsl.fr/index.php/apps/files/download/Shared/ORCHIDEE/REFERENCES/ORCHIDEE-N/Friend_2005.pdf here]), ''the canopy N profile follows a negative exponential decline with depth, with an extinction coefficient (0.11) fitted to the tropical rain forest observations of Carswell et al. (2000)''. In order to conserve the leaf N concentration as calculated for the overall canopy, this tends to define a leaf N concentration at the top of the canopy n0 as
+* In diffuco_trans_cexchange, the impact of leaf N on photosynthesis is based on the former work of Friend (2001, appendix 2, [https://cloud.lsce.ipsl.fr/index.php/apps/files/download/Shared/ORCHIDEE/REFERENCES/ORCHIDEE-N/Friend_2001.pdf here]) that is itself based on the work of Kull and Kruijt (1998, [https://cloud.lsce.ipsl.fr/index.php/apps/files/download/Shared/ORCHIDEE/REFERENCES/ORCHIDEE-N/kull_1998.pdf here]).[[BR]]In this scheme, one assume that the leaf N impacts on Vmax, Jmax and the effective quantum efficiency of the leaf for CO2 uptake (the alpha parameter). The former impact is directly related to the concentration in Chlorophyl which is function of the N concentration (see below).[[BR]] As in Friend and Kiang (2005, eq. 2 and paragraph above, [https://cloud.lsce.ipsl.fr/index.php/apps/files/download/Shared/ORCHIDEE/REFERENCES/ORCHIDEE-N/Friend_2005.pdf here]), ''the canopy N profile follows a negative exponential decline with depth, with an extinction coefficient (0.11) fitted to the tropical rain forest observations of Carswell et al. (2000)''. In order to conserve the leaf N concentration as calculated for the overall canopy, this tends to define a leaf N concentration at the top of the canopy n0 as
 {{{
 ! n0        : nitrogen concentration in the top layer
 …
 / When we calculate the assimalation per canopy layer - contrary to what is done in diffuco_trans_co2, where the thickness of each layer exponentially increases as long as we go deep in the canopy - here in diffuco_trans_cexchange the tickness of the layers is fixed and equals 0.5 (expressed in LAI unit, m2 m-2, variable dlai in the code). Due to the non-linearity of many processes involveld in the photosynthesis scheme (N profile, light profile,...), it is strange to me to consider fixed thickness ... ?
 / The solution that is proposed by Kull and Kruijt (1998) and this is implemented in OCN (cexchange) assumes that Ci (the intercellular CO2 concentration is known). So there is no attempt to solve jointly A (the assimilation), Ci and gs (the stomatal conductance). I don't know we could keep the analytical solution of Yin et al. (2009) with the formulation proposed by Kull and Kruijt.
+/ The solution that is proposed by Kull and Kruijt (1998) and that is implemented in OCN (cexchange) assumes that Ci (the intercellular CO2 concentration is known). So there is no attempt to solve jointly A (the assimilation), Ci and gs (the stomatal conductance). I don't know how we could keep the analytical solution of Yin et al. (2009) with the formulation proposed by Kull and Kruijt.
 / It seems that the N concentration involved in the calculation of Vcmax, Jmax and quantum efficiency in the paper of Kull and Kruijt (named Np) corresponds to the leaf photosynthetic nitrogen. I don't think that Sönke really care of this in OCN (he uses the total leaf N content, to my opinion).
 * In diffuco_trans_co2, the leaf N is impacting Vcmax and Jmax based on the work of Friend et al. (1997, eq. 46 and 47, [https://cloud.lsce.ipsl.fr/index.php/apps/files/download/Shared/ORCHIDEE/REFERENCES/ORCHIDEE-N/friend_1997.pdf here]). See [source:branches/orchidee-N/ORCHIDEE/src_stomate/stomate_vmax.f90@19#L270 here] [[BR]]
  The factor impacting Vcmax and Jmax corresponds the fraction of leaf N present in RubB relatively to the reference fraction. It is a linear function of leaf N content with the following two equations:[[BR]]
+* In diffuco_trans_co2, the leaf N impacts 'only' on Vcmax and Jmax based on the work of Friend et al. (1997, eq. 46 and 47, [https://cloud.lsce.ipsl.fr/index.php/apps/files/download/Shared/ORCHIDEE/REFERENCES/ORCHIDEE-N/friend_1997.pdf here]). See [source:branches/orchidee-N/ORCHIDEE/src_stomate/stomate_vmax.f90@19#L270 here] [[BR]]
+ The factor impacting Vcmax and Jmax corresponds to the fraction of leaf N present in RubB relatively to the reference fraction. It is a linear function of leaf N content with the following two equations:[[BR]]
  f_Rub + 12.5 f_Chl + f_other = 1  (eq. 46)[[BR]]
  and f_other = a0 -  71.4*N [[BR]]
 …
 / a comment of Sönke: ''N effect is fraction in Rubisco (relative to normal) times leaf N relative to normal. It should be based on true calculus, but results with BIOME-BGC/Hybrid formulation are not realistic - don't yet understand the cause of the error''.
 / The formulation used in stomate_vmax is done for the entire canopy using biomass(ileaf,Nitrogen). The inferred scaling factor that accounts for the N-limitation (scal) is then passed to diffuco_trans_co2 where also account for a N-reduction within the canopy as it is done in the trunk version of ORCHIDEE. I think it will be better to account for the N profile as done in diffuco_trans_cexchange and to recalculate the ''scal'' factor for each layer.
+/ The formulation used in stomate_vmax is done for the entire canopy using biomass(ileaf,Nitrogen). The inferred scaling factor that accounts for the N-limitation (scal) is then passed to diffuco_trans_co2 where it also accounts for a N-reduction within the canopy as it is done in the trunk version of ORCHIDEE. I think it will be better to account for the N profile as done in diffuco_trans_cexchange and to recalculate the ''scal'' factor for each layer.
  * Yin et al. (2009) defines also some relationships between Jmax, Vcmax and a parameter that we can relate to the effective quantum efficiency. See [https://cloud.lsce.ipsl.fr/index.php/apps/files/download/Shared/ORCHIDEE/REFERENCES/ORCHIDEE-N/Yin_2009b.pdf here][[BR]]