D.W.G. van Kraalingen

LINGRA, a sink/source model to simulate grassland productivity in Europe

A simulation model for the prediction of the productivity of Lolium perenne L. grasslands is described and validated. Simulated key processes are light utilization, leaf formation, leaf elongation, tillering, and carbon partitioning (storage, shoot, root). Source- and sink-limited growth are simulated independently. Sink-limited growth is characterized by temperature-dependent leaf expansion and tiller development, whereas source-limited growth is determined by photosynthetic light-use-efficiency of the canopy and the remobilization of stored carbohydrates in the stubble. At each integration step, commonly 1 day, the available amount of carbon from the source is compared with the carbon required by the sink. The actual growth is determined by the minimum value of either the sink or the source. If the source is in excess of the sink, the surplus is allocated to storage carbohydrates in the stubble. This storage carbon is available for remobilization at times that the sink requires more carbohydrates than are available from photosynthesis. In contrast to previous grassland models, LINGRA describes regrowth after defoliation in a mechanistic way, balanced by temperature-driven remobilization of stored carbohydrates. In order to validate LINGRA, an extensive set of experimental data was used, derived from measurements at 35 sites in Europe. The average error between the observed and predicted yields was 14% at the level of irrigated, and 19% at the level of non-irrigated, treatments for the whole of Europe.

The Fortran simulation translator, a simulation language

The Fortran simulation translator (FST) is a simulation language, that enables the researcher to develop concepts, in terms of mathematical equations, e.g. about agro-ecological systems, that are converted in a Fortran program with data files (Fortran simulation environment, FSE). This generated Fortran program is well-structured and can be executed using both user developed and standard mathematical library subroutines (e.g. IMSL). The possibility to use the generated Fortran program as a starting point for further model development makes FST a valuable tool, both for research and education.