Dynamic vegetation: No
Nitrogen limitation: - Photosynthesis carboxylation capacity is dependent on leaf N such that, when leaf N is low, photosynthetic capacity is downregulated and, when leaf N is high, photosynthetic capacity is upregulated. Vegetation C:N ratio is flexible. Vegetation upregulates and downregulates symbiotic BNF in response to strong and weak N limitation respectively. See Asaadi and Arora (2021) and Kou-Giesbrecht and Arora (2022).
Co2 effects: - The photosynthesis parametrization is based upon the approach of Farquhar et al. (1980) and Collatz et al. (1991, 1992) as described in Melton and Arora (2016). The gross leaf photosynthesis rate depends upon the maximum assimilation rate allowed by light, Rubisco, and transport capacity, and is dependent on the partial pressure of CO2 in the leaf interior.
Light interception: - The photosynthesis parametrization is based upon the approach of Farquhar et al. (1980) and Collatz et al. (1991, 1992) as described in Melton and Arora (2016). The leaf-level gross photosynthesis rate is scaled up to the canopy-level gross primary productivity by considering the exponential vertical profile of photosynthetically absorbed radiation along the depth of the canopy and leaf area index.
Phenology: - The leaf phenology parametrization is described in detail in Arora and Boer (2005). There are four different leaf phenological states in which vegetation can be at a given instant: (i) no leaves or dormant, (ii) maximum growth, (iii) normal growth and (iv) leaf fall or harvest. PFTs may go through only some, or all, of these phenological states depending on their deciduousness. A broadleaf cold deciduous tree, for example, transitions through all these four states in a year. In winter, the broadleaf cold deciduous trees are in the no leaves or dormant state; favourable climatic conditions in spring trigger leaf growth and the tree enters the maximum leaf growth state when all the NPP is allocated to leaves to accelerate leaf out; when the LAI reaches a threshold the tree enters the normal leaf growth state and NPP is also allocated to the stem and roots; finally the arrival of autumn triggers leaf fall / harvest and the trees go into the leaf fall / harvest state where no NPP is allocated to leaves (but it continues for the stem and roots). When all the leaves have been shed, the trees go into the no leaves or dormant state again and the cycle is repeated the next year. The evergreen tree PFTs and the grass PFTs do not enter the leaf fall / harvest state and maintain a leaf canopy as long as environmental conditions are favourable.
Water stress: - Water stress causes a reduction in photosynthesis and accelerated leaf turnover compared to the normal leaf turnover. Water stress also causes reduced growth efficiency which increases mortality. See Melton and Arora (2016).
Heat stress: - Photosynthesis stops at high and low temperatures because each PFT has specified lower and upper temperature thresholds for photosynthesis. Vapour pressure deficit and soil moisture regulate photosynthesis and are also affected by temperature. Cold stress causes accelerated leaf turnover compared to the normal leaf turnover. See Melton and Arora (2016).
Evapo-transpiration approach: - Total evapotranspiration is comprised of soil evaporation, evaporation of intercepted water and sublimation of intercepted snow from the canopy and plant transpiration. See Sun and Verseghy (2019).
Root distribution over depth: - Root distribution is calculated using a dynamic root distribution (as a function of root biomass). See Arora and Boer (2003).
Closed energy balance: - Yes, the energy balance is closed. Net radiation equals the sum of latent, sensible and ground heat fluxes.
Coupling/feedback between soil moisture and surface temperature: - All soil layers experience moisture phase change as well as internal energy change caused by soil heat conduction and/or soil water mass loss/gain. See Verseghy (2012).
Latent heat: - The top soil layer absorbs solar energy and emits longwave radiation as well as exchanging energy with the overlying air through sensible and latent heat fluxes. See Verseghy (2012).
Sensible heat: - The top soil layer absorbs solar energy and emits longwave radiation as well as exchanging energy with the overlying air through sensible and latent heat fluxes. See Verseghy (2012).
How do you compute soil organic carbon during land use (do you mix the previous pft soc into agricultural soc)?: - When the fractional coverage of a PFT decreases, litter and soil C from the removed fractional coverage of the PFT is uniformly spread over the grid cell. See Arora and Boer (2010).
Do you separate soil organic carbon in pasture from natural grass?: - No (pasture is not represented).
Do you harvest npp of crops? do you including grazing? how does harvested npp decay?: - Crop harvesting is initiated when the daily mean air temperature remains below 8C for 5 consecutive days, or when the crop LAI reaches a threshold (3.5 m2 m−2 for C3 crops and 94.5 m2 m−2 for C4 crops) signifying that the crops have matured. Crop harvesting occurs over a period of 15 days. The harvested crop biomass C contributes to the litter pool. See Arora and Boer (2005). Grazing is not included.
How do you to treat biofuel npp and biofuel harvest?: - Not represented.
Does non-harvested crop npp go to litter in your output?: - Non-harvested crop biomass C remains as live biomass C.
