USDA Forest Service
 

Pacific Southwest Research Station

 

Pacific Southwest Research Station
800 Buchanan Street
Albany, CA 94710-0011

(510) 559-6300

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Research Topics Forest Management

Cone Fire Research - Fire Severity Transect
Effects of thinning and prescribed fire on wildfire severity

Summary of:Skinner, Carl N.; Ritchie Martin W; Hamilton, Todd; Symons, Julie. 2005. Effects of thinning and prescribed fire on wildfire severity. In: Proceedings of the twenty-fifth forest vegetation management conference: 25 years of excellence—where we are, where we've been & where we're going. January 20-22, 2004. Redding, California. pp. 80-91.

Background

The Cone Fire affected three Blacks Mtn. Ecological Research Project (BMERP) treatment units – Two Low Diversity treatments units, one with prescribed fire (LoDF) and one without prescribed fire (LoDNF), and one High Diversity treatment unit with prescribed fire (HiDF).

This research project investigated patterns of fire severity from the Cone fire that burned into the existing treatment areas. Our objectives were to: 1) Describe transitional fire effects primarily on trees, but also on soils, vegetation and woodpecker browsing and 2) Compare the fire effects in treated areas to those in untreated areas.

Study Area

This study is being conducted in the Cone fire-salvaged portion of the Blacks Mountain Experimental Forest (BMEF). The 10,300-acre BMEF was established in 1934. The forest of this area is generally of the inland ponderosa pine type. The fire regime of these forests generally is of the frequent, low-moderate severity type.

Blacks Mountain Ecological Research Project

The BMERP, a long-term, large-scale, interdisciplinary research project, was initiated in 1991 at the Blacks Mountain Experimental Forest (BMEF) in the southern Cascades of northern California. This study was designed to increase our understanding of the effects of forest structural complexity on the health and vigor of interior ponderosa pine ecosystems, quantify the ecosystem’s resilience to natural and human-induced disturbances, and determine how these ecosystems can be managed for sustained resource values (Click to see information about BMEF and BMERP).

Methods

We established 25 strip plots (33ft x 492ft) systematically located perpendicular to the boundaries of the treatment units affected by the Cone Fire to characterize the pattern of fire damage to trees as the fire approached and entered the unit (See image below). Initial observations of surface burn, crown scorch, and bole char indicated that 164ft outside and 328ft inside of treatment units is sufficient to characterize change in fire effects and intensity. The 328ft inside the treatment units was further divided into two 164ft sections to characterize the fire effects in the edge zone and further into the treated area. The centerline of each strip plot was marked. Surface characteristics were noted as surface cover and conditions at each 3.28ft distance along the centerline. (Detailed methods available in full paper.)

Results

Effects Data

When the strip plots are considered together, there appears to be a gradient of fire related tree mortality that follows a gradient of pre-fire stand conditions. This gradient displays the highest mortality where no pre-fire stand thinning had occurred. Generally, where there had been no thinning treatments, mortality exceeded 90% of the stand. Where thinning had not been followed by prescribed fire and surface fuel treatments were limited to lop and scatter, mortality was generally around 40-60% of the stand.

Where thinning had been followed by prescribed fire 2 – 4 years before the Cone Fire, fire related mortality was less than thinning alone. On the LoDF transects, fire related mortality was negligible. In the HiDF transects, there was a gradient of mortality with many trees close to the edge of the treatment area killed, apparently due to radiant heat from outside the unit, since there was little fuel and only a very low intensity fire within the unit that died out quickly.

Conclusion

Clearly differing levels of treatments were associated with dramatic differences in levels of fire-related tree mortality. It should be noted that these data describe the effects of a single fire under a narrow window of weather conditions within the interior ponderosa pine forest type. Therefore, it is a case study and one should be cautious about extrapolating the results to other forest types and to fires occurring under different weather conditions

Last Modified: Sep 12, 2013 07:19:20 PM