How Is a Landscape Represented?

LANDIS-II divides a landscape into sites and ecoregions.

Sites are individual cells (or pixels). Sites have a predetermined resolution. Resolutions can be any positive number, integer or fraction (e.g., 10 or 29.5). For most applications, cell resolution is between 10 and 250 meters. Sites are assumed to be homogeneous in regard to light levels. Each site belongs to one and only one ecoregion.

The site is the basic unit of succession and is responsible for tracking cohort data. Within each site, one or many cohorts react individually to disturbances and succession. Succession occurs separately within each site, although affected by the neighboring landscape due to seed dispersal and disturbances. Other data is also tracked at the site level, dependent upon the extensions being used. Examples include: time-since-last-fire, coarse dead biomass, last-harvesting-prescription applied, etc.

An ecoregion is a group of one or more sites. Ecoregions (or landtypes) represent landscape units that are assumed to have homogeneous climate and soils. Therefore, the ability of species to establish at each site is determined at the ecoregion scale. It is up to the user to decide how large their ecoregions should be, depending on local topography, data available, and research question.

An ecoregion need not be continous and can be dispersed across the landscape. Some ecoregions are non-active: the model will completely ignore inactive ecoregions when doing calculations.