Potential Leaf Area Expansion

The increase of leaf area during the vegetative period, expressed as green leaf area per unit soil area (green leaf area index, GLAI, m2 m -2), is calculated as a function of the crop biomass accumulation.

where ABGd (kg m -2 d -1 ) is the daily rate of biomass produced if the transpiration ratio is bigger than the transpiration limiting factor, SLA (m 2 kg -1 ) is the specific leaf area and p (m 2 kg -1 ) is a partition coefficient controlling the fraction of biomass apportioned to leaves (a value of zero apportions all biomass to leaves).

Leaf area duration, expressed in thermal time units (GDDgreen , °C-d), is assigned to each unit of daily leaf area produced. When a given portion of green area completes its duration, it is removed from current GLAI , effectively simulating the process of leaf senescence. The fraction of leaf area produced each day is initialized as zero degree-days, and the thermal time during the life of this fraction is calculated daily from the crop development.

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