Background: Forest management, especially restoration, is informed by understanding the dominant natural disturbance regime. In many western North American forests, the keystone disturbance is fire, and a plethora of research exists characterizing various fire regime parameters, although often only one or two parameters are addressed in individual studies. I performed a systematic review of the literature and meta-analysis of the derived data from 26 publications to characterize five parameters of the historical fire regime of ponderosa pine (Pinus ponderosa Lawson & C. Lawson) ecosystems in Colorado, USA: fire frequency, severity, extent, seasonality, and climate.

Results: The collection of evidence indicates a fire regime predominantly characterized by moderate to high frequency, low- and mixed-severity fires that occurred in late summer to fall, with fires occurring in drier than average years that were often preceded by two to three years of wetter than average conditions. The overall average mean fire return interval (MFI) was 21 years (SD = 1.4 years, n = 78 sites) and increased with site elevation (r = 0.33, P < 0.05). Low- and mixed-severity fires accounted for 83% of all observations, and 69% of fires occurred in late summer to fall with no relationship found between latitude and seasonality. Geographic region (Front Range and southwestern Colorado) was associated with variability in fire regime parameter values, with southwestern Colorado sites having a stronger association with wetter than average conditions in the three years preceding fire years and a shorter mean MFI (18 years) relative to Front Range sites (23 years). Data were insufficient to evaluate changes in fire severity and extent due to a lack of historical information, as well as differences in sampling methods and reporting.

Conclusion: This meta-analytic approach identified variation within and among fire regime parameter values that occurred along elevational and geographic axes, and this information should be useful to managers engaging in forest restoration aimed at enhancing resilience of fire-adapted forests to disturbance and climate change.