| 233 | | Describes r6614. 70% 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. |
| 234 | | |
| 235 | | 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 trunk no longer depend on a prescribed longevity. |
| 236 | | |
| | 233 | Describes r7451. 70% of the global forests are managed, which contradicts the assumption in previous versions of ORCHIDEE that forests are long-lived natural vegetation types. 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, one of the key principles of ORCHIDEE-FM were retained. This principle is reflected in the rule of Deleuze and Dhote that allocates carbon to different diameter classes based on the basal area of the tree. Tree growth is followed by relative-density index (RDI)-based management which enforces thinning and harvest operations based on the current tree density, RDI and the maximum density which in turn is based on the observed (large-scale) self-thinning density. |
| | 234 | Good to know: the forest management approach is embedded in the carrying capacity of a stand which has been formalized through the self-thinning relationship which makes use of two parameters '''alpha_self_thinnin''' 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'''. |
| | 235 | |
| | 236 | 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. Mortality is governed by an RDI which in turn is a function of quadratic mean stand diameter. 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. |
| 243 | | 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 (see ticket #647). Set '''read_fm_map''' to y and specify the location of the forest management map in COMP/stomate.card. Check OOL_SEC_STO_FG4 for an example of how the existing map should be defined and used. |
| 244 | | |
| 245 | | 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 : 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'''. |
| 246 | | |
| | 243 | 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. ORCHIDEE now has a rather detailed management reconstruction for Europe and a rather coarser global management reconstruction. Set '''read_fm_map''' to y and specify the location of the forest management map in COMP/stomate.card. Check OOL_SEC_STO_FG4 for an example of how the existing map should be defined and used. |
| | 244 | |
| | 245 | 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 : harvest diameter '''max_harvest_dia''', coppice diameter '''coppice_diameter''', rotation length '''src_rot_length''', number of rotations '''src_nrots''', fuelwood diameter '''fuelwood_diameter''' and 4 parameters specifying the upper RDI and 4 parameters specifying the lower RDI: '''a_rdi_xxx_yyy''' (intercept), '''b_rdi_lower_yyy''' (slope), '''c_rdi_xxx_yyy''' (upper limit) and '''d_rdi_xxx_yyy''' (lower limit) where xxx stands for lower or upper. This set of 8 parameters is defined for yyy = man (ifm = 2, thin and fell) and yyy = unman (ifm =1, unmanaged). |
| 266 | | Describes r7089. Vegetation height is dynamic; as the PFT (in particular forests) grow, the height will grow through the allocation. When multiple circumferences classes are used, height has an impact on where the carbon goes. Due to intra-stand competition, more carbon gets allocated to taller circumference classes. Disturbances can change the average stand height. Self-thinning is a natural process in which small trees die because they are out-competed for resources. Environmental mortality is another natural process in which larger trees are killed as they are assumed to be more sensitive to environmental stress. Windthrow is an (optional) process which will disproporationally impact taller trees. In runs using forest management (not currently the default), forests can be thinned from above or below. Forests thinned from above lose tall trees to harvest, while those thinned from below lose small trees. Both actions change the average height of the stand. |
| 267 | | |
| 268 | | Vegetation height has an impact on roughness height (aerodynamic properties of the surface). |
| 269 | | |
| 270 | | PFTs are prescribed by choosing the height of the saplings, which determines initial biomass through allometric relations. |
| 271 | | |
| 272 | | Two variables are output for each PFT: "HEIGHT", which is the average height of the vegetation (averaged across all circumference classes), and "HEIGHT_DOM", which is the dominant height (the height of the largest circumference class). A switch was introduced in r7083 which allows one or the other to be used in the calculation of the roughness height. |
| | 259 | Describes r7451. Vegetation height is dynamic; as the PFT (in particular forests) grow, the height will grow through the allocation. When multiple circumferences classes are used, height has an impact on where the carbon goes. Due to intra-stand competition, more carbon gets allocated to taller circumference classes. Disturbances can change the average stand height. Self-thinning is a natural process in which small trees die because they are out-competed for resources. Environmental mortality is another natural process in which larger trees are killed as they are assumed to be more sensitive to environmental stress. Windthrow is an (optional) process which will disproportionally impact taller trees. In runs using forest management (not currently the default), forests can be thinned from above or below. Forests thinned from above lose tall trees to harvest, while those thinned from below lose small trees. Both actions change the average height of the stand. |
| | 260 | The parameters '''pipe_tune3''' and '''pipe_tune2''' link tree diameter to tree height. Where pipe_tune3 is the tree height (m) for a tree with a diameter of 1 meter. Those parameters determine the diameter-height relationship but the height growth is mostly driven by stand mortality. Many trees need to die early on during stand development to reach realistic height growth rates. That is the reason why the RDI of young stands is rather low (0.3 to 0.4 -> determined by '''d_rdi_xxx_yyy''') Vegetation height has an impact on roughness height (aerodynamic properties of the surface). |
| | 261 | Two variables are output for each PFT: "HEIGHT", which is the average height of the vegetation (averaged across all circumference classes), and "HEIGHT_DOM", which is the dominant height (the height of the largest circumference class). A switch was introduced in r7083 which allows one or the other to be used in the calculation of the roughness height. |
| | 262 | |
