LANDFIRE ›› Frequently Asked Questions (FAQs)

Q.	How does LANDSUM model succession and disturbance?

Succession is modeled as a deterministic process. The residence time and deterministic succession pathway of each succession class is defined during vegetation modeling workshops. Once the time spent in a given succession class exceeds its residence time, the succession class transitions to the next succession class. Succession operates at the stand level, which refers to contiguous areas in the same age of the same succession class within a biophysical setting. Disturbances are modeled as stochastic processes. Non-fire disturbances, such as wind-throw, insect outbreaks, and flooding, are simulated at the stand level. In contrast, fire disturbances are ignited within stands and are spread across the landscape according to a percolation algorithm that integrates Rothermel (1991) fire spread relationships with topography and wind. The fire burns until constrained by a stochastically chosen maximum size or unburnable areas. The effects of all disturbances are manifest in transitions between succession classes (such as a replacement-severity fire) or changes in successional age. For more information, refer to Keane and others 2002.

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Rothermel, R. C. 1991. Predicting behavior and size of crown fires in the Northern Rocky Mountains. Research Paper INT-438, United States Department of Agriculture, Forest Service Intermountain Forest and Range Experiment Station, Ogden, Utah USA.

Keane, R. E., R. Parsons, and P. Hessburg. 2002. Estimating historical range and variation of landscape patch dynamics: Limitations of the simulation approach. Ecological Modelling 151:29-49.