Long-Term Effects of Fuel Reduction Treatments on Surface Fuel Loading in the Blue Mountains of Oregon

Kat E Morici,John D Bailey

doi:10.3390/f12101306

Abstract

Fire exclusion and a lengthening fire season has resulted in an era of megafires. Fuel reduction treatments in forested ecosystems are designed to guard against future extreme wildfire behavior. Treatments create a heterogenous landscape and facilitate ecosystem function and resilience in fire-adapted forests of the western United States. Despite widespread recognition that repeated fuel treatments are needed to maintain desired stand characteristics over time, few field studies have evaluated treatment longevity. The Blue Mountains Fire and Fire Surrogate site in northeastern Oregon presented an opportunity to investigate woody fuel loading 15–17 years after four treatments: mechanical thin, prescribed burn, both thin and burn, and no treatment control. The principal findings were: (1) fine fuel load 15 years post-burn remained slightly below pre-treatment values; (2) rotten coarse fuel load was reduced post-burn, but sound coarse fuel was not altered by any active treatment; and (3) total woody fuel load 15–17 years post-treatment was similar to pre-treatment values. Understanding surface fuel loading is essential for predicting fire behavior. Overall, the effects of fuel reduction treatments on woody surface fuels were transitory in dry mixed conifer forests. Frequent maintenance treatments are recommended to protect values at risk in areas with high fire hazards. Quantifying the persistence of changes in forest conditions aids in the planning and analysis of future fuel treatments, along with scheduling maintenance of existing treated areas.

Highlights

Dry forests of the western United States co-evolved with fire, a disturbance that alters plant communities through successional processes
At the end of the study, only the thin and burn treatment remained below the target basal area (BA), and all active treatments remained below the target fine fuel loading
We examined woody surface fuel loading changes over time following common fuel treatments

Summary

Introduction

Dry forests of the western United States co-evolved with fire, a disturbance that alters plant communities through successional processes. Plant and animal communities depend on fire as an essential disturbance for the structural diversity it generates [1]. A forest that supports a mix of successional stages is predicted to be more resilient to future disturbance [2]. Recent management practices have directly and indirectly homogenized the structure and composition of many dry forests in the western United States, prompting concerns about wildfire and sparking debate over future management [3,4,5]. The cost of fighting wildland fire is rising quickly, and is likely to continue with increasing human encroachment into the wildland–urban interface, rising mid-summer temperatures in the western United States, and lengthening fire seasons [6]

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