Fig. 2: Range-average % forest stability index (FSI) of the eight most abundant tree species in the western US over the period 2001–2018.
From: Over half of western United States' most abundant tree species in decline
Population decline (red) occurs when the FSI is negative and the associated 95% confidence interval does not include zero. Conversely, population expansion (blue) occurs when the FSI is positive and the associated confidence interval does not include zero. Here, the %FSI is a direct measure of average annual percent change in the relative density of each species across their ranges in the western US. Thus, total % change in relative density can be estimated by multiplying the %FSI by the length of the study period (18 years). For reference, complete loss of a species over the study period would be indicated by a %FSI value of −5.56%. Source data are provided as a Source Data file.
