Community growth adjustment by environmental and seasonal factors

The functions limit the growth of all plant species without any species-specific reduction:

The growth is adjusted for environmental and seasonal factors $EN{V}_t$ [-] that apply in the same way to all species:

$$EN{V}_t=RA{D}_t\cdot TEM{P}_t\cdot SE{A}_t$$

with the radiation $RA{D}_t$ [-], temperature $TEM{P}_t$ [-], and seasonal $SE{A}_t$ [-] growth adjustment factors.

Radiation influence

The growth reducer due to too much radiation $RA{D}_t$ [-] is described by:

$$RA{D}_t=max(min(1,1-{\gamma }_{RAD,1}\cdot (PA{R}_t-{\gamma }_{RAD,2})),0)$$

• ${\gamma }_{RAD,1}$ controls the steepness of the linear decrease in radiation use efficiency for high $PA{R}_t$ values [ha MJ⁻¹]

• ${\gamma }_{RAD,2}$ threshold value of $PA{R}_t$ from which starts a linear decrease in radiation use efficiency [MJ ha⁻¹]

Visualization

steepness of the reduction γ_RAD_1	4.45e-6
PAR at which the growth is reduced γ_RAD_2	50000

API

GrasslandTraitSim.radiation_reduction! Function

radiation_reduction!(; container, PAR)

Reduction of radiation use efficiency at high radiation levels.

source

Temperature influence

The growth reduction factor due to too low or too high temperature $TEM{P}_t$ [-] is described by:

$$TEM{P}_t=\{\begin{array}{ll}0& \text{if }{T}_t<{\omega }_{TEMP,T_1}\\ \frac{T_t-{\omega }_{TEMP,T_1}}{{\omega }_{TEMP,T_2}-{\omega }_{TEMP,T_1}}& \text{if }{\omega }_{TEMP,T_1}<T_t<{\omega }_{TEMP,T_2}\\ 1& \text{if }{\omega }_{TEMP,T_2}<T_t<{\omega }_{TEMP,T_3}\\ \frac{{\omega }_{TEMP,T_4}-T_t}{{\omega }_{TEMP,T_4}-{\omega }_{TEMP,T_3}}& \text{if }{\omega }_{TEMP,T_3}<T_t<{\omega }_{TEMP,T_4}\\ 0& \text{if }{T}_t>{\omega }_{TEMP,T_4}\end{array}$$

Equation are from Jouven et al. (2006) and theses are based on Schapendonk et al. (1998).

• ${\omega }_{TEMP,T_1}$ minimum temperature for growth [°C]

• ${\omega }_{TEMP,T_2}$ lower limit of optimum temperature for growth [°C]

• ${\omega }_{TEMP,T_3}$ upper limit of optimum temperature for growth [°C]

• ${\omega }_{TEMP,T_4}$ maximum temperature for growth [°C]

Visualization

minimum temperature for growth ω_TEMP_T1	4
lower limit of optimum temperature for growth ω_TEMP_T2	10
upper limit of optimum temperature for growth ω_TEMP_T3	20
maximum temperature for growth ω_TEMP_T4	35

API

GrasslandTraitSim.temperature_reduction! Function

temperature_reduction!(; container, T)

Reduction of the growth if the temperature is low or too high.

source

Seasonal effect

The seasonal growth adjustment factor $SE{A}_t$ [-] is desribed by:

$$\begin{array}{rl}SE{A}_t& =\{\begin{array}{ll}{\zeta }_{SEAmin}& \text{if}S{T}_t<200°C\\ {\zeta }_{SEAmin}+({\zeta }_{SEAmax}-{\zeta }_{SEAmin})\cdot \frac{S{T}_t-200°C}{{\zeta }_{SEA,S{T}_1}-400°C}& \text{if}200°C<S{T}_t<{\zeta }_{SEA,S{T}_1}-200°C\\ {\zeta }_{SEAmax}& \text{if}{\zeta }_{SEA,S{T}_1}-200°C<S{T}_t<{\zeta }_{SEA,S{T}_1}-100°C\\ {\zeta }_{SEAmin}+({\zeta }_{SEAmin}-{\zeta }_{SEAmax})\cdot \frac{S{T}_t-{\zeta }_{SEA,S{T}_2}}{{\zeta }_{SEA,S{T}_2}-{\zeta }_{SEA,S{T}_1}-100°C}& \text{if}{\zeta }_{SEA,S{T}_1}-100°C<S{T}_t<{\zeta }_{SEA,S{T}_2}\\ {\zeta }_{SEAmin}& \text{if}S{T}_t>{\zeta }_{SEA,S{T}_2}\end{array}\\ S{T}_t& =\sum _{i=tmod365}^{t}max(0°C,T_i-0°C)\end{array}$$

This empirical function was developed by Jouven et al. (2006).

• ${\zeta }_{SEA,S{T}_1}$ threshold of the yearly accumulated temperature, above which the seasonality factor decreases from ${\zeta }_{SEAmax}$ to ${\zeta }_{SEAmin}$ [°C]

• ${\zeta }_{SEA,S{T}_2}$ threshold of the yearly accumulated temperature, above which the seasonality factor is set to ${\zeta }_{SEAmin}$ [°C]

• ${\zeta }_{SEAmin}$ minimum value of the seasonal effect [-]

• ${\zeta }_{SEAmax}$ maximum value of the seasonal effect [-]

Visualization

ζ_ST₁	775
ζ_ST₂	1450
minimum value of the seasonal effect ζ_SEAmin	0.7
maximum value of the seasonal effect ζ_SEAmax	1.3

API

GrasslandTraitSim.seasonal_reduction! Function

seasonal_reduction!(; container, ST)

Adjustment of growth due to seasonal effects.

source