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Reference Condition Models

Rapid Assessment Reference Condition Models were created from 2004 to 2005 through a series of expert workshops and a review process. Each model can be downloaded in two parts: a VDDT Model and a Model Description. Information on these is provided below.

VDDT Models can be downloaded for the entire western or eastern United States, and Model Descriptions can be downloaded for the entire western or eastern United States, for model zones, or for individual potential natural vegetation groups (PNVGs) - see links at right (metadata accompany all downloads).

VDDT Models

Each PNVG was modeled quantitatively using the VDDT (Vegetation Dynamics Development Tool) software. VDDT is a public domain, aspatial, user-friendly modeling tool, available from ESSA Technologies. The VDDT data include quantitative information about the rates and pathways of succession and the frequency and effects of disturbances.

Model Descriptions

Each model includes comprehensive documentation that describes the vegetation, geography, biophysical characteristics, succession stages, and disturbance regimes of each PNVG. Descriptions also document the assumptions behind, the outstanding questions about, the contributors to, the resources used for, and the evolution of each model. In addition, model descriptions describe the results of the VDDT modeling and can be used as reference conditions for the Interagency Fire Regime Condition Class Guidebook procedures.

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