Environmental Engineering Reference
In comparison to crops, some simplifications have been made:
Leaf area is calculated only as a function of environmental factors and species
type and not of dry matter accumulation.
Over the reproductive phase, stem biomass accumulation is calculated as a fraction
of the above-ground herbage mass (Calvière and Duru 1999) .
The root mass is considered constant over the growing season (as in many herbage
growth models, e.g. Schapendonk et al. 1998 ; Barrett et al. 2005) ; i.e. root growth
rate is assumed to be the same as the root death rate.
In grass-legume mixtures, the competition between the two components is not
simulated. An a priori sward composition is defined that depends on the nitrogen
and defoliation management.
FieldManager: Spatial Information for Multiple Plant Species
The FieldManager component, which was developed by INRA, provides field
dimension information for heterogeneous stands such as agroforestry plots or
vineyards where rows of trees or other woody perennials separate cultivated strips
of either crop or grassland. Field configuration is defined by three parameters:
WidthIntraRow (distance between trees in a row), WidthInterRow (distance
between rows), WidthCultivatedStrip (width of cultivated strip between each row).
Three field configurations are currently available: for crop alone, for a continuous
row of grapevine with a cultivated strip of Crop or Grassland, for a row of timber
trees with a cultivated strip of crop.
LightInterception: Light Interception and Competition by Canopies
The LightInterception component, which was developed by INRA, implements
models that estimate the daily interception of solar radiation partitioned between
one or two types of plant and the soil. From the daily solar radiation, a simple
field description (from FieldManager) and a small number of plant parameters
that characterize canopy dimensions (LAI, crown dimension), this component
estimates the fraction and amount of PAR (Photosynthetic Active Radiation)
intercepted by the tree canopy, any crop or grassland canopy below, and the soil.
Three models are available in the current version, all derived from the geometrical
model of Pronk et al. (2003) , but corresponding to different field configurations
(continuous rows, rows of cubes, or rows of cuboids). These models assume
homogeneity in the light transmission properties of leaves and uniform
canopies (this assumption is needed to permit the one-dimension simplification
of canopy structure in other parts of the model). In the case of a single crop
the model follows the Beer-Lambert law (Monteith and Unsworth 1990) for light