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Table 4 Fire severity classification results from studies in ponderosa pine ecosystems in Colorado, USA, used in the fire regime meta-analysis of 2017. n = number of sample units

From: Systematic review and meta-analysis of fire regime research in ponderosa pine (Pinus ponderosa) ecosystems, Colorado, USA

 Fire severity (%)nTime periodRegion
ReferenceLowMixedHigh   
Bigio et al. 2016 a3169013Before 1880Southwestern
Ehle and Baker 2003 b9037801540 to 2000Front Range
Schoennagel et al. 2011 c07921201601 to 1953Front Range
Sherriff 2004 d72208861700 to 1920Front Range
Sherriff et al. 2014 e128801501597 to 1995Front Range
Williams and Baker 2012a f552421131984 to 2009Front Range
Williams and Baker 2012b g33364145Before 1880Front Range
Mean severity (%SE)38 (36)45 (28)17 (49) 
  1. aFire severity estimated within plots through time:
  2.  • low: ≥1 fire-scarred tree was present within 2 ha of the plot and no distinct cohorts were evident.
  3.  • mixed:
  4.   ° ≥1 fire-scarred tree present and ≥1 distinct cohort evident, or
  5.   ° no fire-scarred trees present, but ≥1 distinct cohort evident and one surviving tree established prior to the cohort.
  6.  • high: no fire-scarred trees, ≥1 distinct cohort, and no surviving trees established prior to the cohort.
  7. bFire severity estimated within plots based on tree mortality and regeneration patterns:
  8.  • low: no or low mortality and little or no regeneration.
  9.  • mixed: mortality of at least one small group of trees within 10 m of each other.
  10.  • high: high overstory mortality and a subsequent large regeneration pulse.
  11. cFire severity estimated within plots through time, based on relative proportions of trees that survived fires (remnant) and trees that established ≤40 years after fire (establishment):
  12.  • low: ≥80% remnant, ≤20% establishment.
  13.  • moderate: 21 to 79% remnant, 79 to 21% establishment.
  14.  • high: ≤20% remnant, ≥80% establishment.
  15. dFire severity estimated for fires within sites based on relative proportions of live trees that survived fire (remnant) and trees that established ≤40 years after fire (establishment), in addition to tree spatial pattern and ring-width changes:
  16.  • low: ≥40% remnant, <20% establishment.
  17.  • moderate: <70% remnant, 20 to 70% establishment.
  18.  • high: <20% remnant, >70% establishment.
  19. eFire severity estimated at each site using the same criteria as Schoennagel et al. 2011, then assigned site-level severity classification of cumulative effects over time.
  20. fFire severity estimated with Monitoring Trends in Burn Severity (MTBS) data of 13 fires >400 ha. MTBS assigns four severity classes (unburned to low, low, moderate, high) to the area of each fire. Results are percent severity class for combined 13 fires. MTBS severity classes “unburned to low” and “low” were combined as Low here for consistency and comparison with the other studies.
  21. gFire severity estimated using General Land Office survey data to reconstruct historical stand structures, which were used to derive percent severity for 260 ha polygons in a 65 525-hectare area, based on the assumptions that tree size is related to tree age and that stand structure and disturbance severity are linked. Polygon severity classified as:
  22.  • low:
  23.   ° mean tree density was <178 trees ha−1
  24.   ° the percentage of large trees was >29.2%, and
  25.   ° the percentage of small trees was <46.9%.
  26.  • mixed: remaining areas (i.e., influenced by fires of moderate severity or a mosaic of different severities).
  27.  • high: percentage of small trees was >50% and percentage of large trees <20%.