Changes between Version 71 and Version 72 of Documentation/TrunkFunctionality4


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Timestamp:
11/12/20 13:32:30 (19 months ago)
Author:
luyssaert
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  • Documentation/TrunkFunctionality4

    v71 v72  
    9696 
    9797=== Allocation === 
    98 Describes r6742. ORCHIDEE trunk uses the allometric allocation as developed in O-CN. In ORCHIDEE trunk the approach was adjusted to work for more than one diameter class. Since it was developed this allocation has been used in ORCHIDEE-CN and ORCHIDEE-CNP. In those branches only a single diameter class was used. Except for the way the reserves and labile pools are calculated (incl. the pseudo sugar loading), the allocation scheme remained rather similar between the aforementioned versions. The model is, however, very sensitive to the way the reserves and labile pools are calculated. The allocation makes use of a labile pool for which the activity is calculated based on the temperature. This sensitivity is important at the start and the end of the growing seasons when temperatures may be low. As such the model addresses the sink/source discussion initiated by Körner. Whereas this approach resulted in an acceptable interannual variability in for example NPP in ORCHIDEE-CAN, adding N seems to have dampen the interannual variability a lot/too much. This dampening was observed in ORCHIDEE-CN  and ORCHIDEE-CN-CAN. IN ORCHIDEE-CNP the temperature relationship was removed (hence NPP and GPP are strictly coupled) because the interannual variability became unrealistic.  
     98Describes r6930. ORCHIDEE trunk uses the allometric allocation as developed in O-CN. In ORCHIDEE trunk the approach was adjusted to work for more than one diameter class. Since it was developed this allocation has been used in ORCHIDEE-CN and ORCHIDEE-CNP. In those branches only a single diameter class was used. Except for the way the reserves and labile pools are calculated (incl. the pseudo sugar loading), the allocation scheme remained rather similar between the aforementioned versions. The model is, however, very sensitive to the way the reserves and labile pools are calculated. The allocation makes use of a labile pool for which the activity is calculated based on the temperature. This sensitivity is important at the start and the end of the growing seasons when temperatures may be low. As such the model addresses the sink/source discussion initiated by Körner. Whereas this approach resulted in an acceptable interannual variability in for example NPP in ORCHIDEE-CAN, adding N seems to have dampen the interannual variability a lot/too much. This dampening was observed in ORCHIDEE-CN  and ORCHIDEE-CN-CAN. IN ORCHIDEE-CNP the temperature relationship was removed (hence NPP and GPP are strictly coupled) because the interannual variability became unrealistic.  
    9999 
    100100There are no options to revert to the allocation based on resource limitation (Friedlingstein et al. 1999). All references and parameters for allocation based on resource limitation have been removed from the code (those that were overlooked can be removed). Allometric allocation makes use of the following PFT-specific parameters: '''sla''', '''longevity_root''', '''longevity_leaf''', '''longevity_sap''', '''pipe_density''', '''tree_ff''', '''pipe_tune_x''', '''k_latosa_max''', and '''k_latosa_min'''. In addition to this set of parameters that mainly describe the allometric relationships and the longevity of the different tissues, the calculation of the allocation coefficients makes use PFT-specific tissue conductivities, i.e., '''k_sap''', '''k_belowground''', and '''k_leaf''' (see also plant water stress). Details on the parameters can be found in the SI of Naudts et al 2015 in GMD or in src_parameters/constantes_mtc.f90.  
    101101 
    102 Previously there was a functional link between C and N-allocation and the hydraulic architecture of a plant because both approaches used the same parameter k_root. In ORCHIDEE-CAN k_root described the conductivity of the fine roots and the soil. In ORCHIDEE trunk this joined conductivity has been split in a fine root conductivity and a soil to root conductivity. Allocation should make use of both conductivities but soil to root conductivity cannot be easily calculated when needed in the allocation. This is subject to future developments. Accounting for the soil to root conductivity in the allocation would imply an adaptation of plant growth to its environment.   
     102Previously there was a functional link between C and N-allocation and the hydraulic architecture of a plant because both approaches used the same parameter k_root. In ORCHIDEE-CAN k_root described the conductivity of the fine roots and the soil. In ORCHIDEE trunk this joined conductivity has been split in a fine root conductivity and a soil to root conductivity. Allocation should make use of both conductivities but soil to root conductivity cannot be easily calculated when needed in the allocation. This is subject to future developments. Accounting for the soil to root conductivity in the allocation would imply an adaptation of plant growth to its environment. 
     103 
     104Crown area is calculated from tree diameter by making use of '''pipe_tune1''' and '''pipe_tune_exp_coeff'''. Since r6933, '''pipe_tune1''' and '''pipe_tune_exp_coeff''' can be calculated as a function of respectively '''pipe_tune2''' and '''pipe_tune3'''. This has became the default setting. For that reason '''pipe_tune1''' and '''pipe_tune_exp_coeff''' are undefined but the parameters '''crown_to_height''' and '''crown_to_height_exp''' need to be set. If one wants the crown diameter to be 66% of the tree height, '''crown_to_height''' needs to be set to 0.66 and '''crown_to_height_exp''' to 2. As long as '''crown_to_height_exp''' equals to 2, '''crown_to_height''' should range between 0 and 0.99. If a different values for '''crown_to_height_exp''' it should be checked that the crown diameter never exceeds the tree height as this will make the model crash with a clear error message.    
    103105 
    104106