User’s manual for a multispecies simulation model of grassland producers and consumers

Abstract

The simulation model of White (1984a,b,c) is a dynamic (time-dependent), deterministic, difference equation, compartment model with 1-day time steps and variable coefficients. The program language is SIMCOMP 2.1 (Gustafson and Innis, 1973), a machine-independent compiler sub-set of SIMCOMP 2.0 (Gustafson and Innis, 1972) and SIMCOMP 3.0 (Gustafson, 1978), with user defined routines and functions written in FORTRAN IV code. The model simulates carbon (mass/m²) and the skeletal structure admits a wide range of perennial grassland simulation conditions such as: primary production dynamics with or without consumers single producer species or multi species canopy composition single or multi-compartment root and soil profile zonation single or multi species consumer dynamics natural population cycles and managed stocking selective and transitional herbivory of plant tissues irrigation and fertiliser applications. The structure is also canonical for different plant forms (based on phenological time scales) and for consumer metabolism (based on homoiothermy and poikilothermy). Consumers are further categorised as diurnal or nocturnal, and feed either below-ground (on roots) or aboveground (on other plant tissues). In addition to structural options, there are diverse functional options based on the user's choice of variable parameters for initialisation (Table I). All parameters must be initialised, but a wide range of options exists to negate various program structures (e.g. the elimination of flowering, snow conditions, and the herbage preferences of consumers) with default values (e.g. 0 or 1). Parameter categories in Table I (see column headings) are based on the enumerated groupings of White (1984b, Tables I and II; 1984c, Table I), and are expanded to include operational 'control variables'.