Description of CBI

The CBI provides a generalized rating of post-fire conditions in the field. It was intended to reference a 30-meter diameter plot, and the conditions as they appear during the first growing season after fire. Thus, CBI typically includes potential latent effects, such as delayed mortality and survivorship, to gauge the average severity for the plot.

In contrast to nominal categories of severity, CBI was designed as an ordinal scale to better relate to continuous remote sensing data, and to offer the potential for higher resolution in the description of severity. It was hoped that CBI also could avoid common misconceptions that may arise when severity is classified into broad low, medium and high categories.

The CBI ranges from 0.0 to 3.0 (unburned to highest severity). It represents an average of selected, observable fire effects throughout a plot. The fire effects are considered as rating factors and individually scored 0.0 to 3.0 (unburned to highest severity). Rating factors are grouped into five potential strata occurring on the plot, including A) substrates, B) vegetation < 1 meter tall, C) vegetation 1-5 meters tall, D) intermediate-sized trees, and E) big trees. There are four to five rating factors per stratum.

There is a hierarchical series of ecological levels with which to interpret and apply the CBI. Rating factor scores within each stratum are averaged to represent a severity index for that stratum. Next, rating factor scores within the lower three strata (A-C) are averaged to obtain a CBI that estimates severity of the understory. Similarly across the upper two strata (D-E), rating factor scores are averaged to get a CBI assessment for the overstory. Finally, all rating factor scores are averaged over all strata, to obtain a total plot CBI as an evaluation of the overall severity across the whole plot.

Currently, the CBI photo series displays plot photos with CBI averages for the 5 individual strata, the understory and overstory, and for the total plot. Links to photo enlargements provide a brief summary of individual rating factors. A complete description of the CBI is available from the FIREMON link on our opening page.

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