Previous versions of LANDIS use 10-year time step to simulate long term forest dynamics. This coarse resolution may not be adequate to capture finer temporal events such as harvesting and natural disturbances. LANDIS 6.0 uses variable time step ranges from 1 to 10 years. Thus it can simulate forest dynamics using longer time steps (e.g., 5-10 years) and disturbance and management using shorter time steps (e.g., 1-3 years). In addition, the effects of environmental change such as climate change can be incorporated by using new functions that modify species establishment probabilities. LANDIS 6.0 preserves the ecological design of LANDIS 4.0 and 5.0.
In LANDIS, a landscape is modeled as a grid of cells (or sites) with vegetation information stored as attributes for each cell. At each cell, the model tracks a matrix containing a list of species by rows and the 10-year age cohorts by columns. The temporal scales of LANDIS are largely dictated by the current 10-year age-cohort structure, and the 10-year time step makes the model suitable for simulating long-term dynamics (101-103 years). The spatial scales of LANDIS are within 103 - 107 ha, depending on the simulation cell size. Since LANDIS tracks only the presence absence of species age cohorts, not individual trees, computational loads are greatly reduced. In addition, the essential information of presence/absence is relatively independent of cell size, and therefore LANDIS is capable of simulating forest succession at cell sizes ranging from 10 to 500 m (He et al. 1999a).
The LANDIS model can be represented conceptually as a repeating cycle of processes that operate on the initial input map and subsequent time steps. Major model dynamics include (a) successional dynamics, (b) species-site quality interactions, and (c) disturbance and management. Succession occurs within a cell based on species life history attributes such as shade tolerance and longevity. Species-site quality interactions involve filtering species based upon their ability to establish on a particular cell based on propagule availability (seed or sprouting ability) in relation to the land type, a spatial landscape input that may correspond to soils, slope, or other physical characteristics. Disturbance and management simulate wind, fire, insect and disease, forest harvesting, and fuel management activities that interact with species/age cohorts in both spatial and temporal dimension (Mladenoff 2004).
Time step in LANDIS 6.0 is varied from 1 to 10 years. The shorter time step is suitable for short-term simulation and the longer time step is suitable for long-term simulation.