WORK IN PROGRESS: Evolution of the functionality of the ORCHIDEE model

Table 1. Concise description of processes (in alphabetical order) simulated in subsequent model versions

CHECKED?	Process	ORCHIDEE Krinner et al. 2005	ORCHIDEE v2.1 Peylin et al.	ORCHIDEE branch 3.0 Vuichard et al 2019	ORCHIDEE svn Milestone 4.0 Naudts et al. 2015
Yes	Age classes	Not available	Not available	Not available	Age classes were introduced to better handle heterogeneity at the landscape level. Age classes are independent of the number of diameter classes. Using age classes adds a lot of details to both the biophysics and the biogeochemistry following natural disturbances, forest management and land cover change. Age classes are defined as separate PFTs that form an age group (​More)
No	Albedo (background)
No	Albedo (snow)
Yes	Albedo (vegetation)	For each PFT the total albedo for the grid square is computed as a weighted average of the vegetation albedo and the background albedo. The background albedo is composed by a snow and soil albedo. The soil albedo depends on the soil properties.	Rather than using soil properties, ORCHIDEE v2.1 uses spatially explicit observation-derived estimates for its background albedo in the absence of snow.	No changes from the previous version.	ORCHIDEE trunk 4 makes use of a two stream radiative transfer scheme through the canopy, extended to multiple canopy levels (​More). The scheme is based on Pinty et al 2006. This approach accounts not only for the leaf mass but also for the vertical and horizontal distribution of the leaf mass (= canopy structure), calculating an effective LAI based on the solar angle. Light from collimated (black sky) and diffuse (white sky) sources are used, and both are weighted equally as information about this partitioning is not yet available in forcing data (​More).
No	Allocation	Carbon is allocated to the plant following resource limitations (Friedlingstein et al 1999). Plants allocate carbon to their different tissues in response to external limitations of water, light and nitrogen availability. When the ratios of these limitations are out of bounds, prescribed allocation factors are used.	No changes		No changes
No	Anthropogenic species change	Not applicable	Not applicable	Not applicable	Describe
No	Bare soil
No	Bark beetles	Not applicable	Not applicable	Not applicable	Describe
No	Biogeography	Describe what was done in Krinner et al 2005	Zhu et al 2.1or MICT?	No changes	Not yet available in this version
No	Biological volatile emissions	Not applicable	Why was it added? What is added?	No changes	No changes
No	C13	Not applicable	Not applicable	Not applicable	Describe
No	Consistency checks	Not applicable	Water balance checks	No changes	Carbon budget checks, nitrogen budget checks and surface area checks
No	Croplands	Describe what was done in Krinner et al 2005	No changes	No changes	crop harvest ends up in harvest pool
No	Diameter classes	Not applicable	Not applicable	Not applicable	Describe
No	Energy budget	The coupled energy balance scheme, and its exchange with the atmosphere, is based on that of Dufresne and Ghattas (2009). The surface is described as a single layer that includes both the soil surface and any vegetation. The energy budget is solved with an implicit numerical scheme that couples the lower atmosphere to the surface, in order to increase numerical stability.	No changes	No changes	No changes
Yes	Interception	Describe what was done in Krinner et al 2005.	Don't know	Don't know	same as ORC3.0
No	Multi layer energy budget	Not applicable	Not applicable	Not applicable	Describe
No	Forest management and management changes	Not applicable	Not applicable	Not applicable	Describe
No	Grass and crop harvest	Describe what was done in Krinner et al 2005.	No changes	No changes	Half of the daily grass turnover is moved in the short lived product pool. At the time crops are harvested all of the harvest which is half of the biomass is moved into the short lived product pool.
No	Growth respiration	A prescribed fraction of 28 % of the photosynthates allocated to growth is used in growth respiration (McCree?, 1974). The remaining assimilates are distributed among the various plant organs using the allocation scheme	No changes	No changes	No changes
No	Land cover change	Not applicable	Piao et al 2205?	No changes	Same method but also works for age classes
No	Litter raking	Not applicable	Not applicable	Not applicable	Describe
No	Litter resistance to evaporation	Not applicable	Describe DO_RSOIL	No changes	No changes
No	Maintenance respiration	Maintenance respiration contributes together with growth respiration to the autotrophic respiration. Maintenance respiration occurs in living plant compartments and is a function of temperature, biomass and, the prescribed carbon/nitrogen ratio of each tissue (Ruimy et al., 1996)	No change	Describe the changes	No changes
No	Mortality and turnover	All biomass pools have a turnover time. Living biomass except the sapwood is transferred to the litter pool, litter is decomposed or transferred to the soil pool. Sapwood is converted into heartwood.	No changes	No changes	Woody biomass no longer has a turnover pool. Trees are killed self-thinning or harvest. Depending on the cause of the mortality the carbon is entirely moved into the litter pool (for self-thinning) or mainly moved into the harvest pool with the remainder contributing to the litter pool (for harvests).
No	Nitrogen cycle	Not applicable	Not applicable	Describe	Added fungivores to make it work with abrupt mortality rather than constant mortality
No	Phenology	At the end of each day, the model checks whether the conditions for leaf onset are satisfied. The PFT-specific conditions are based on long and short term warmth and/or moisture conditions (Botta et al., 2000).	No changes	No changes	No changes
No	Photosynthesis	C3 and C4 photosynthesis is calculated following Farquhar et al. (1980) and Collatz et al. (1992), respectively. A semi-analytical approach is used to solve the set of equations for photosynthesis, stomatal conductivity and internal CO2 concentration in the leaf at the PFT level.	The semi-analytical solution was replaced by an analytical solution (Yin and Streuk 2009). The Vcmax parameter was redefined. The analytical solution is faster than the semi-analytical solution and by redefining vcmax, large observational database could be used to parameterize the model	No changes	LAI layering
No	Plant water stress	Describe what was done in Krinner et al 2005	No change	No change	Added hydraulic architecture
No	Prescribe initial vegetation	Describe what was done in Krinner et al 2005	No change	Describe	Describe additional changes
No	Pseudo sugar loading	Not applicable	Not applicable	Describe	No change
No	Product use	Not applicable	Piao et al 2005	Previously product pools were only accounted when land cover change was activated. In an experiment where land cover change was followed by a treatment with land cover change the product pool was frozen during the second part of the experiment. This has been changed such that the decomposition of the product pool is calculated irrespective of whether land cover change is activated or not.	Previous version assign fixed values of the wood harvest to the short, medium and long-lived product pools. The model now has two approaches: (1) the previous approach with fixed ratios between the pools and a dynamic approach in which wood below a certain diameter goes into the short lived pool and wood above a certain diameter is distributed over the medium and long-lived product pool according to fixed values. The definition (=longevity) of the short, medium and long-lived is no longer fixed as before but became a user setting
No	Recruitment (with PFT map)	Not applicable	Not applicable	Not applicable	Describe
No	Roughness	Describe how it is calculated in Krinner et al 2005	Roughness is observed to be different for heat and momentum. Also the roughness is driven by the leaf area. The formulation of Shu et al.is now used to account for the leaf area when calculating a separate roughness length for heat and momentum.	No changes	No changes
No	Routing	Not applicable	How is it calculated in ORCHIDEE 2.1. \citep{NgoDuc2007}?	No changes	No changes
No	Senescence	Describe how senescence is calculated in Krinner et al 2005.	No changes	No changes	No changes
No	Snow temperature and dynamics	Describe snow energy budget in Krinner et al 2005	How is it calculated now? See Tao	No changes	No changes
No	Soil hydrology	Describe bucket model. Calculated for X soil columns.	Vertical water flow in the soil is based on the Fokker-Planck equation that resolves water diffusion in non-saturated conditions from the Richards equation (Richards, 1931). The 4 m soil column consists of eleven moisture layers with an exponentially increasing depth (D'Orgeval et al., 2008). Bare soil, short vegetation, and tall vegetation each have their own water column.	No changes	No changes
No	Soil and litter carbon and heterotrophic respiration	Following Parton et al. (1988), prescribed fractions of the different plant components go to the metabolic and structural litter pools following senescence, turnover or mortality. The decay of metabolic and structural litter is controlled by temperature and soil or litter humidity. For structural litter, its lignin content also influences the decay rate.	If there is insufficient N available to support the decomposition of the litter and soil carbon, heterotrophic respiration will be limited by the Nitrogen availability	No changes	No Changes
No	Soil maps	Describe how senescence is calculated in Krinner et al 2005.	Added USDA	No changes	No changes
No	Soil temperature	The soil temperature is computed according to the Fourier equation using a finite difference implicit scheme with seven numerical nodes unevenly distributed between 0 and 5.5 m (Hourdin, 1992). ? How many soil temperature columns did we have ?	The differences in the vertical discretisation between the soil hydrology and soil temperature resulted in difficulties to conserve energy. The soil hydrology and temperature are calculated on a single vertical discretisation. A separate soil temperature is calculated for the bare soil, short vegetation, and tall vegetation.	No changes	No changes
No	Specific leaf area	Describe what was done in krinner et al 2005	No change	Describe dynamic LAI	No change
No	Spin-up	Describe what was done in krinner et al 2005	Analytical spinup	No change	No change
No	Tree ring width	Not applicable	Not applicable	The essential calculations are made in the allocation subroutine and are available in this version. The calculations are not further processed neither written to the history files	Describe what was done.
No	Vegetation distribution	Krinner et al 2005 describes global vegetation by 13 meta-classes (MTCs) with a specific parameter set (one for bare soil, eight for forests, two for grasslands and two for crop-lands)	The implementation of the MTC was generalized such that more than one PFT can be used to represent an MTC. ORCHIDEE 2.1 uses 13 MTCs to define 15 PFTs.	No changes	No changes
No	Vertical discretization soil carbon	Not applicable	Not applicable	Describe	No change
No	Wood harvest	Not applicable	Wood harvest following LUHv2 maps. LUHv2 prescribes the amount of biomass to be harvested. Wood harvest is accounted for at the PFT level.	No changes	LUHv2 maps are used to decide whether the forests in a pixels are managed or not. If the forest is managed, ORCHIDEE calculates the harvested biomass following an RDI approach.
No	Wind throw	Not applicable	Not applicable	Not applicable	Describe