Species-specific growth adjustment - Light

We define two different methods for distributing the total potential growth of the community among all species. In both methods, the result is defined in the light comptetition factor $LI{G}_{txys}$ [-].

Method 1: Simple light competition, implemented in light_competition_simple!

$$\begin{array}{rl}LI{G}_{txys}& =\frac{LA{I}_{txys}}{LA{I}_{tot,txy}}\cdot {\left(\frac{H_{txys}}{H_{cwm,txy}}\right)}^{{\beta }_{LIG,H}}\\ H_{cwm,txy}& =\sum _{s=1}^S\frac{B_{txys}}{B_{tot,txy}}\cdot H_{txys}\end{array}$$

Method 2: Use vertical height layers, implemented in light_competition_height_layer!

In the second method, we derive the proportion of light intercepted by each species out of the total light intercepted by dividing the sward into vertical height layers of constant width, by default $0.05m$:

$$\begin{array}{rl}LI{G}_{txys}& =\sum _{z=l}^{L}LI{G}_{txy,l}\\ LI{G}_{txys,l}& =IN{T}_{txy,l}\cdot \frac{LA{I}_{txys,l}}{LA{I}_{tot,txy,l}}\cdot \frac{1}{1-\exp ({\gamma }_{RUE,k}\cdot LA{I}_{tot,txy})}\\ IN{T}_{txy,l}& =\exp ({\gamma }_{RUE,k}\cdot \sum _{z=l+1}^{L}LA{I}_{tot,txy,z})\cdot (1-\exp ({\gamma }_{RUE,k}\cdot LA{I}_{tot,txy,l}))\end{array}$$

• ${\beta }_{LIG,H}$ controls how strongly taller plants get more light for growth, only used in the first method without height layers [-]

• ${\gamma }_{RUE,k}$ light extinction coefficient, only used in the method with height layers [-]

Visualization

• Effect of plant height on light competition for the simple method (darker colours) and the method with height layers (brighter colours). To simplify matters in the visualization for the simple method, we use the leaf area index fraction to calculate the community-weighted mean height.

simple method: control how strongly taller plants get more light β_LIG_H
layer method: light extinction coefficient γ_RUE_k [-]
Leaf area index species 1
Leaf area index species 2
Height species 2

simple method:

layer method:

• Visualization of the light competition in the height layers

Leaf area index species 1 [-]
Leaf area index species 2 [-]
Height species 1 [m]
Height species 2 [m]
Light extinction coefficient γ_RUE_k [-]

API

GrasslandTraitSim.light_competition! Function

light_competition!(
;
    container,
    above_biomass,
    actual_height
)

Calculate the distribution of potential growth to each species based on share of the leaf area index and the height of each species.

source

GrasslandTraitSim.light_competition_simple! Function

light_competition_simple!(
;
    container,
    above_biomass,
    actual_height
)

Method 1: Simple light competition based on the height of each species.

source

GrasslandTraitSim.light_competition_height_layer! Function

light_competition_height_layer!(; container, actual_height)

Method 2: Divide the grassland into vertical layers and calculate the light competition for each layer.

source