6.7. jules_vegetation.nml

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

6.7.1. 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_gleaf_fix
Type:logical
Default:T

Switch for fixing a bug in the accumulation of g_leaf_phen_acc.

This bug occurs because veg2 is called on TRIFFID timesteps and veg1 is called on phenol timesteps, but veg1 did not previously accumulate g_leaf_phen_acc in the same way as veg2.

TRUE
veg1 accumulates g_leaf_phen_acc between calls to TRIFFID. This is important if triffid_period > phenol_period.
FALSE
veg1 does not accumulate g_leaf_phen_acc between calls to TRIFFID.
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_stem_resp_fix
Type:logical
Default:F

Switch for bug fix for stem respiration to use balanced LAI to derive respiring stem mass. The switch is included for backwards compatability with existing configurations. Future updates should include this change.

TRUE
Respiring stem mass is derived allometrically.
FALSE
Respiring stem mass varies with seasonal LAI
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:1-6
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 a 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.
  6. This is an improvement of option 5, including an exponential decline of leaf N with canopy height proportional to LAI, following Beer’s law.

Note

When using can_rad_mod = 4, 5 or 6 it is recommended to use driving data that contains direct and diffuse radiation separately rather than a constant diffuse fraction.

See also

Descriptions of options 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). Options 1 to 5 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.