Leaf area and ground coverage

The daily change in the crop’s leaf area index is calculated in MONICA as follows:

\[\frac{d}{dt} LAI = \frac{d}{dt} W_{L+} \cdot \left( \Phi_{L_s} + \frac{DD_{ads}}{DD_{crops}} \cdot (\Phi_{L_e} - \Phi_{L_s}) \cdot dt \right) -\frac{d}{dt}W_{L-} \cdot \Phi_{L_0} \cdot dt\]

\(LAI\) Leaf area index \([m^2 \, m^{-2}]\)
\(W_{L+}\) Leaf biomass increment \([kg \, TM \, m^{-2} \, d^{-1}]\)
\(W_{L-}\) Leaf biomass decrement \([kg \, TM \, m^{-2} \, d^{-1}]\)
\(\Phi_{L_s}\) Specific leaf area at begin of stage \([m^{2} \, kg \, TM^{-1}]\)
\(\Phi_{L_e}\) Specific leaf area at end of stage \([m^{2} \, kg \, TM^{-1}]\)
\(\Phi_{L_0}\) Initial specific leaf area \([m^{2} \, kg \, TM^{-1}]\)
\(DD_{acts}\) Actual temperature sum of developmental stage \([^{\circ}C \, d]\)
\(DD_{crops}\) Plant-specific temperature sum in developmental stage \([^{\circ}C \, d]\)
\(t\) Time \([d]\)

Subsequently, the ground coverage is calculated from leaf area index:

\(\beta = 1 - e^{-0.5 \cdot LAI}\)

\(\beta\) Degree of ground coverage \([m^{2} \, m^{-2}]\)
\(LAI\) Leaf area index