6.8. jules_vegetation.nml

This file sets the vegetation options. It contains one namelist called JULES_VEGETATION.

6.8.1. JULES_VEGETATION namelist members

JULES_VEGETATION::l_q10

Type:logical Default:T

Switch for use of Q10 approach when calculating soil respiration.

TRUE

Use Q10 approach.

Note

This is always used if TRIFFID is switched off (l_triffid = FALSE) and was used in JULES2.0.

FALSE

Use the approach of the RothC model.

JULES_VEGETATION::l_trait_phys

Type:logical Default:F

Switch for using trait-based physiology.

TRUE

Vcmax is calculated based on observed leaf traits. Leaf nitrogen (nmass: kgN kgLeaf-1) and leaf mass (LMA: kgLeaf m-2) can be based on observations from the TRY database. Vcmax (umol CO2 m-2 s-1) is based on linear regressions as in Kattge et al. 2009. Two additional parameters are needed: vint and vsl - the intercept and slope, respectively, that relate the leaf nitrogen to vcmax. Sigl is replaced with LMA (sigl=LMA*Cmass, where Cmass is the kgC/kgLeaf and is 0.4).

FALSE

Vcmax is calculated based on parameters nl0 (kgN kgC-1) and neff.

Note

Trait based physiology is not currently compatible with the crop model.

JULES_VEGETATION::l_phenol

Type:logical Default:F

Switch for vegetation phenology model.

TRUE

Use phenology model.

FALSE

Do not use phenology model.

JULES_VEGETATION::l_triffid

Type:logical Default:F

Switch for dynamic vegetation model (TRIFFID) except for competition.

TRUE

Use TRIFFID. In this case soil carbon is modelled using four pools (biomass, humus, decomposable plant material, resistant plant material).

FALSE

Do not use TRIFFID. A single soil carbon pool is used.

JULES_VEGETATION::l_veg_compete

Type:logical Default:T

Switch for competing vegetation.

Only used if l_triffid = TRUE.

TRUE

TRIFFID will let the different PFTs compete against each other and modify the vegetation fractions.

FALSE

Vegetation fractions do not change.

JULES_VEGETATION::l_ht_compete

Type:logical Default:F

Only used if l_triffid = TRUE.

TRUE

Use height-based vegetation competition.

This allows for a generic number of PFTs, and is implemented by lotka_noeq_jls.F90 and lotka_eq_jls.F90 depending on the setting of l_trif_eq.

FALSE

Use the standard competition.

This is hard-wired for 5 PFTs with co-competition for grasses and trees in lokta_jls.F90.

JULES_VEGETATION::l_trif_eq

Type:logical Default:T

Switch for equilibrium vegetation model (i.e., an equilibrium solution of TRIFFID).

Only used if l_triffid = TRUE.

TRUE

Use equilibrium TRIFFID.

FALSE

Do not use equilibrium TRIFFID.

JULES_VEGETATION::phenol_period

Type:integer Permitted:>= 1 Default:None

Period for calls to phenology model in days. Only relevant if l_phenol = TRUE.

JULES_VEGETATION::triffid_period

Type:integer Permitted:>= 1 Default:None

Period for calls to TRIFFID model in days. Only relevant if one of l_triffid or l_trif_eq is TRUE.

JULES_VEGETATION::l_bvoc_emis

Type:logical Default:F

Switch to enable calculation of BVOC emissions.

TRUE

BVOC emissions diagnostics will be calculated.

FALSE

BVOC emissions diagnostics will not be calculated.

JULES_VEGETATION::l_o3_damage

Type:logical Default:F

Switch for ozone damage.

TRUE

Ozone damage is on.

Note

Ozone concentration in ppb must be prescribed in prescribed_data.nml.

FALSE

No effect.

JULES_VEGETATION::l_landuse

Type:logical Default:F

Switch for using landuse change in conjunction with TRIFFID

Only used if l_triffid = TRUE.

TRUE

Land use change is implemented within TRIFFID. Litter fluxes are split between soil and wood product pools. Requires additional prognostics covering the product pools and the agricultural fraction from the previous TRIFFID call.

FALSE

All litter fluxes enter the soil

JULES_VEGETATION::l_recon

Type:logical Default:T

Switch for reconfiguring land fractions prior to TRIFFID call.

Only used if l_triffid = TRUE.

TRUE

For soil points (land points with no ice) set vegetation fractions to their minimum values and reduce bare soil fraction accordingly.

FALSE

Do not apply the minimum vegation fractions. This is useful when some points are 100% lake and urban, in which case reconfiguration leads to a total tile fraction of greater than 1.

JULES_VEGETATION::l_prescsow

Type:logical Default:F

Switch that determines how crop sowing dates are defined. Only used if ncpft > 0.

TRUE

Sowing dates prescribed in JULES_CROP_PROPS are used.

FALSE

Sowing dates are determined by the model.

JULES_VEGETATION::l_irrig_dmd

Type:logical Default:F

Switch controlling the implementation of irrigation demand code. Tiles will be irrigated to critical point from an unconstrained water supply.

TRUE

Tiles are irrigated to critical point.

FALSE

No effect.

JULES_VEGETATION::irr_crop

Type:integer Permitted:1 or 2 Default:1

1. When to irrigate is determined from driving data according to Doell & Siebert (2002) method.
2. When to irrigate is determined by maximum dvi across all tiles. Requires l_crop = T.

JULES_VEGETATION::can_model

Type:integer Permitted:1-4 Default:4

Choice of canopy model for vegetation:

1. No distinct canopy.
2. Radiative canopy with no heat capacity.
3. Radiative canopy with heat capacity. This option is deprecated, with 4 preferred.
4. As 3 but with a representation of snow beneath the canopy. This option is preferred to 3.

Note

can_model = 1 does not mean that there is no vegetation canopy. It means that the surface is represented as a single entity, rather than having distinct surface and canopy levels for the purposes of radiative processes.

JULES_VEGETATION::can_rad_mod

Type:integer Permitted:1-5 Default:4

Switch for treatment of canopy radiation.

1. A single canopy layer for which radiation absorption is calculated using Beer’s law. Leaf-level photosynthesis is scaled to the canopy level using the ‘big leaf’ approach. Leaf nitrogen, photosynthetic capacity, i.e the Vcmax parameter, and leaf photosynthesis vary exponentially through the canopy with radiation.
2. Multi-layer approach for radiation interception following the 2-stream approach of Sellers et al. (1992). This approach takes into account leaf angle distribution, zenith angle, and differentiates absorption of direct and diffuse radiation. Leaf-level photosynthesis is calculated using a vertically-varying light-limited rate, and constant Rubisco and export velocities, consistent with the assumption of constant leaf N through the canopy. Canopy photosynthesis and conductance are calculated as the sum over all layers.
3. As 2, but photosynthesis calculated separately for sunlit and shaded leaves for the whole canopy (i.e. not at each layer). The definition of sunlit and shaded leaves is based on a threshold of absorbed radiation at each layer.
4. This is a modification of option 2. Instead of constant leaf N through the canopy, it has an exponential decline of leaf N with canopy height. Additionally includes inhibition of leaf respiration in the light.
5. This is an improvement of option 4, including:
   • Sunfleck penetration though the canopy.
   • Division of sunlit and shaded leaves within each canopy level.
   • A modified version of inhibition of leaf respiration in the light.

Note

When using can_rad_mod = 4 or 5, it is recommended to use driving data that contains direct and diffuse radiation separately rather than a constant diffuse fraction.

See also

Descriptions 1, 2 and 3 can be found in Jogireddy et al. (2006), and an application of option 4 can be found in Mercado et al. (2007) and all are described in Clark et al (2011).

JULES_VEGETATION::ilayers

Type:integer Permitted:>= 0 Default:10

Number of layers for canopy radiation model.

These layers are used for the calculations of radiation interception and photosynthesis.

JULES_VEGETATION::frac_min

Type:real Default:1.0e-6

Minimum fraction that a PFT is allowed to cover if TRIFFID is used.

JULES_VEGETATION::frac_seed

Type:real Default:0.01

Seed fraction for TRIFFID.

JULES_VEGETATION::pow

Type:real Default:5.241e-4

Power in sigmodial function used to get competition coefficients.

See Hadley Centre Technical Note 24 Eq.3.