W. K. Lauenroth
D. P. Coffin
H. H. Shughart; T. M. Smith
Environmental Sciences Departement
University of Virginia, Charlottesville
T. B. Kirchner
Natural Resource Ecology Laboratory
Colorado State University, Fort Collins
Colorado 80523, USA.
VEGOMAT (Smith et al. 1989) is a framework for linking individual-based
gap models which can operate simultaneously at number of spatial scales.
The prototype version operates at three spatial scales corresponding to plot
sizes for simulating the dynamics of herbs, shrubs and trees. Each spatial
scale operates as a seperate submodel; these interface via plant influence on
environmental conditions and the process of recruitment. The largest spatial
scale corresponds to a gap-model plot for trees, with progressively smaller
plots for shrubs and grasses. The plots are nested in that each of the smaller
plots is a sub-plot of the plot at the next larger scale, thus maintaining the
spatial context of nestedness: the shrub plots can be viewed as samples within
the larger tree plot, and similarly the grass plots as samples within the
The vertical profile is continuous, with a defined minimum and maximum height for each spatial scale (submodel). Each scale operates as a conventional gap-model; however, as individuals grow they can pass from one scale to the next larger as they increase in height. This process of recruitment from one scale to the next is carried out as a probabilistic process based on sample statistics for replicate plots at the next lower level. In turn, the large plots act as a constraint on the small next lower level. In turn, the large plots act as a constraint on the small scales by modifying the environmental conditions of plots within them. For example, the available light at the top of the vertical profile for a shrub plot is defined by the leaf area of the larger tree plot to which it belongs. Thus, the framework is one of the large plots acting as a context for the small, and the small plots providing a statistical distribution of recruitment to the large.
(from : Lauenroth, W.K.; Urban, D.L.; Coffin, D.P.; Parton, W.J.; Shugart, H.H.; Kirchner, T.B.; Smith, T.M.; 1993 : Modeling vegetation structure - ecosystem process interactions across sites and ecosystems. Ecological Modelling (67), P. 49 - 80.)