Dynamic development

Simulations of the temporal development of leaf area index, canopy height, albedo and root depth are based on biomass, i.e. carbon content in the plant, when the switch for plant growth is “on” (refer to the Nitrogen and Carbon chapter). Simulations of the temporal development of all these plant properties always take place when growth is simulated, although these values are not further used in the abiotic part of the simulation if the temporal development of a certain plant property has been chosen as static.

When simulating temporal development by the plant growth model some empirical functions are used to convert figures on biomass to the appropriate physical attributes of the plant. Parameters for these conversions are found in a parameter table: Size and shape of growing plant.

The Leaf area index, A_l, is estimated as:

                                                                          (3.4)

where p_l,sp is a parameter and B_l is the total mass of leaf (i.e. the carbon content in the leaves, C_Leaf +C_OldLeaf). See viewing function Simulated Leaf Area Index.

The canopy height, H_p, is estimated as:

      (3.5)

where p_hmax, p_h1, p_h2, p_h3 and p_h4 are parameters. B_ag is the above ground biomass (i.e. the carbon content in the leaves and stem, C_Leaf + C_OldLeaf + C_Stem + C_OldStem), ∆t_pl is the time that has elapsed since the emergence day (i.e. plant age) and C_grain is the carbon content in the grain pool. See viewing function Simulated Canopy Height.

The albedo, a_veg, may be specified differently depending on if the plant is in a vegetative stage, a_pveg, or a grain stage, a_pgrain, of plant development. The growth stage index is used to interpolate between the two values in the grain filling stage:

•      Vegetative stage:

•      Grain stage:

where:                                          (3.6)
and GSI is the growth stage index described in the “Nitrogen and Carbon” chapter.

The root depth, z_r, is estimated as:

                                                       (3.7)

where p_zroot and p_incroot are parameters and B_r is the mass of roots (i.e. the carbon content in the roots, C_Roots +C_OldRoots). See viewing function Simulated Root Depth.

The root length, L_r, is estimated as:

                                                                         (3.8)

where p_rl.sp is a parameter and B_r is the mass of roots (i.e. the carbon content in the roots, C_Roots). The old root biomass is not considered since these roots are assumed to play a minor role for water uptake.