Changes between Version 18 and Version 19 of Documentation/TrunkFunctionality4


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Timestamp:
2020-03-09T14:39:48+01:00 (4 years ago)
Author:
luyssaert
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  • Documentation/TrunkFunctionality4

    v18 v19  
    163163 
    164164 
    165  
    166  
    167 ++++ CONTINUE CHECKING +++++ 
    168  
    169  
    170165=== Forest management and management changes (CHECK) === 
    17116670% of the global forests are managed, which contradicts the assumption in previous versions of ORCHIDEE that forests are long-lived natural vegetation. Forest management, inspired by ORCHIDEE-FM, was implemented in ORCHIDEE-CAN. Owing to the allometric allocation scheme, the introduction of diameter classes and a canopy structure, only the principles of ORCHIDEE-FM, i.e., the allocation rule of Deleuze and Dhote that allocates carbon to different diameter classes based on the basal area of the tree, and relative-density index (RDI)-based management which enforces thinning and harvest operations based on the current tree density and the self-thinning density, were retained.  
    172167 
    173 The forest management strategy can either be forced as a single value to all PFTs and grid cells, or be read from an input map to allow for spatially and temporally varying strategies.  If the forest management strategy is not specified the default value "unmanaged" (FM = 1) is used. This implies that the stand is never thinned or harvested. Once the stand density drops below the threshold or the tree diameter exceeds a different threshold, a stand replacing disturbance occurs and a new stand is prescribed in the next time step. Therefore, the biomass pools in ORCHIDEE-CN-CAN no longer depend on a prescribed longevity. 
    174  
    175 When developing and testing the model, a single forest management strategy can be applied for all pixels and PFTs. Set '''read_fm_map''' to n and specify the desired management strategy (1-4) through '''forest_managed_forced'''. ORCHIDEE-CN-CAN distinguishes 4 different strategies: 
     168The forest management strategy can either be forced as a single value to all PFTs and grid cells, or be read from an input map to allow for spatially and temporally varying strategies.  If the forest management strategy is not specified the default value "unmanaged" (FM = 1) is used. This implies that the stand is never thinned or harvested. Once the stand density drops below the threshold or the tree diameter exceeds a different threshold, a stand replacing disturbance occurs and a new stand is prescribed in the next time step. Therefore, the biomass pools in ORCHIDEE trunk 4 no longer depend on a prescribed longevity. 
     169 
     170When developing and testing the model, a single forest management strategy can be applied for all pixels and PFTs. Set '''read_fm_map''' to n and specify the desired management strategy (1-4) through '''forest_managed_forced'''. ORCHIDEE trunk 4 distinguishes 4 different strategies: 
    176171* FM=1 unmanaged 
    177172* FM=2 high stand management: with RDI based thinnings and density/diameter based final harvest 
    … …  
    179174* FM=4 short rotation coppice with willow or poplar 
    180175 
    181 For applications that focus on forestry or require landscape heterogeneity, a PFT-specific management strategy can be read from a spatially explicit map. Thus, the same PFT in different pixels can be assigned a different management strategy. However, within a pixel a single PFT can only have one management strategy. Unless, one wants to run forest management over Europe the user will have to create his/her forest management maps first. Set '''read_fm_map''' to y and specify the location of the forest management map in COMP/stomate.card. Check the existing forest management maps for Europe for an example of how the map should be defined. 
    182  
    183 +++UPDATE+++ 
    184 Dynamic RDI was implemented and prescribe has been changed 
    185 When prescribing a forest stand (independent of forest management) the Initial density '''nmaxtrees''', and the range of the initial tree height of the seedlings needs to be specified '''height_init_min''' and '''height_init_max'''. Irrespective of the management strategy the maximum carrying capacity needs to be described. Carrying capacity was formalized through the self-thinning relationship which makes use of two parameters '''alpha_self_thinning''' and '''beta_self_thinning'''. As a fail-safe option the longevity of a stand is still defined but will only be used when all other criteria fail to kill the stand (not observed). Longevity is defined by the parameter '''residence_time'''. 
    186 ++++++++++++ 
    187  
    188 The details of each of the 4 management strategies can be refined through a set of PFT-specific parameters. Note that not every management strategy makes use of all parameters. For more details see the SI of Naudts et al 2015 (last table).  The different management strategies require parameter values for : first thinning height '''h_first''', stand replacing density '''ntrees_dia_profit''', harvest diameter '''max_harvest_dia''', coppice diameter '''coppice_diameter''', rotation length '''src_rot_length''', number of rotations '''src_nrots''', fuelwood diameter '''fuelwood_diameter''' and the minimum and maximum alpha and beta (thus 4 parameters) specifying the RDI range '''alpha_rdi_upper''', '''alpha_rdi_lower''', '''beta_rdi_upper''' and '''beta_rdi_lower'''. 
     176For applications that focus on forestry or require landscape heterogeneity, a PFT-specific management strategy can be read from a spatially explicit map. Thus, the same PFT in different pixels can be assigned a different management strategy. However, within a pixel a single PFT can only have one management strategy. Unless, one wants to run forest management over Europe the user will have to create his/her forest management maps first (see ticket #647). Set '''read_fm_map''' to y and specify the location of the forest management map in COMP/stomate.card. Check the existing forest management maps for Europe for an example of how the map should be defined. 
     177 
     178Carrying capacity was formalized through the self-thinning relationship which makes use of two parameters '''alpha_self_thinning''' and '''beta_self_thinning'''. As a fail-safe option the longevity of a stand is still defined but will only be used when all other criteria fail to kill the stand (not observed). Longevity is defined by the parameter '''residence_time'''. 
     179 
     180The details of each of the 4 management strategies can be refined through a set of PFT-specific parameters. Note that not every management strategy makes use of all parameters. For more details see the SI of Naudts et al 2015 (last table).  The different management strategies require parameter values for : harvest diameter '''max_harvest_dia''', coppice diameter '''coppice_diameter''', rotation length '''src_rot_length''', number of rotations '''src_nrots''', fuelwood diameter '''fuelwood_diameter''' and the minimum and maximum alpha and beta (thus 4 parameters) specifying the RDI range '''alpha_rdi_upper''', '''alpha_rdi_lower''', '''beta_rdi_upper''' and '''beta_rdi_lower'''. 
    189181 
    190182According to economic theory, high-stand forest are harvested when the actual growth drops below the long-term growth. This has been implemented in ORCHIDEE-CAN and ORCHIDEE-CN-CAN. This feature was found to be very sensitive to the time frame for which actual increment was calculated. This option can be by-passed by setting this period unrealistically high, for example, '''n_pai''' =1000. Persons interested in further testing/developing this feature should set this parameter (unit: years) to 5 or 10. 
    191183 
    192 While developing the code some conflicts were encountered between RDI and self-thinning. As a first solution an additional threshold was introduced '''rdi_limit_upper'''. When debugging progressed this threshold was set to 0.99 (if set to 1.00 there is no correction any more). The initial problem was resolved but the initial fix has not been removed yet. For the time being set rdi_limit_upper to 0.99. Persons interested in simplifying the code could start with this removing this parameter. 
    193  
    194184Following a disturbance (which could be a clear cut), tree species changes and forest management change can be prescribed or read from a map in ORCHIDEE-CAN. Set '''lchange_species''' = y, '''read_species_change_map''' = y, and '''read_desired_fm_map''' = y and specify the paths of those maps in the COMP/stomate.card. This functionality replaces the DGVM in areas where humans rather than nature govern species distribution, for example, Europe. Note that there are some constraints on the possible management changes. If the species is a conifer, for example, the new management strategy cannot be coppicing (fm=3). Anthropogenic species change has not been developed to work together with land cover change (this would require some good bookkeeping for veget_max). Forest management change has not been tested together with land cover change but because they affect different variables, i.e., '''forest_managed''' and '''veget_max''' combining both functionalities seems not overly complex. 
     185 
    195186 
    196187=== Grasslands (r6614) === 
    … …  
    211202The functionality to simply prescribe an lai value (either through impose or by reading a map) will need to be replaced by functionality that prescribes or reads the biomass, leaf age, and number of individuals. Given that the current lai map is based on a previous ORCHIDEE run, the same approach could be used to generate a spatially explicit canopy map that contains biomass, individuals and leaf age distribution. Nevertheless, reading an observed lai, i.e., from MODIS, and using it to force ORCHIDEE trunk 4 would require a substantial number of assumptions to turn an aggregated 1D lai value into a disaggregated 3D canopy at the PFT level. 
    212203 
     204++++ CONTINUE CHECKING +++++ 
     205 
     206 
    213207 
    214208=== Land cover change (with age classes) (CHECK) === 
    … …  
    220214 
    221215=== Litter decomposition (CHECK) === 
     216 
    222217After large-scale dieback events (with a closed n-cycle, i.e., impose_cn = n), so much soil mineral N becomes immobilized to decompose litter that too little N is left for plant regrowth. To address this, we implicitly represent the action of fungivores, which eat the decomposing fungi and release N for the plants and increase N turnover rates. We set aside a fraction of qd (stomate_litter.f90) which becomes available for plant uptake in nitrogen_dynamics. This fraction is calculated and is at its maximum when the litter pool is large compared to the biomass pool. The fraction is at its lowest when the living biomass is high compared to the litter biomass. The implemented principle mimics a Lokta-Volta dynamic where the predator are the fungivores and the prey the fungi. The share of the N contained in the decomposing fungi that is released as an excrement from the fungivores ranges between 0 and 1 and is calculated. 
    223218 
    … …  
    409404The code allows for many more combinations than described above. Some of those configuration could be useful in specific cases but be aware of the following: 
    410405* If the restart file for sechiba does not come from the same simulation/year as the restart file for stomate, the values for the variables that are stored in both sechiba and stomate will be overwritten by the values stored in the stomate restart file because that file is read later in the initialization phase. Some variables are duplicated because that adds the flexibility to the configuration that can be used to restart the model. 
    411 * When '''read_lai''' is true, '''ok_stomate''' should be false (but this is not yet enforced by the model). It may work but it is flawed from a conceptual point of view. read_lai was developed for cases where the model cannot simulate its own canopy. ok_stomate was developed so the model would simulate its own canopy. 
     406* When '''read_lai''' is true, '''ok_stomate''' should be false (but this is not yet enforced by the model - see ticket #685). It may work but it is flawed from a conceptual point of view. read_lai was developed for cases where the model cannot simulate its own canopy. ok_stomate was developed so the model would simulate its own canopy. 
    412407* Combining a sechiba restart from with '''impveg''', '''impsoil''' or '''laimap''' may result in values from the restart file being overwritten because impveg, impsoil and laimap are checked after reading the sechiba restart file. 
    413408* NCO commands could be used to hack into the restart file. This could be powerful when stomate is used and one wants to restart the model after a spin-up but also want that the forest starts growing the first year of the simulation. In that case circ_class_biomass and circ_class_n should be set to zero. This approach is straightforward when no age classes are used. When age classes are used many more variables need to be moved to the correct PFT to avoid conflicts.