Fuel treatments in shrublands experiencing pinyon and juniper expansion result in trade-offs between desired vegetation and increased fire behavior

Fire Ecology

Original Research

Eva K. Strand¹  Claire Tortorelli²  Lisa M. Ellsworth³  Claire L. Williams³  Scott E. Shaff⁴  Beth A. Newingham⁵  Matt C. Reeves⁶  Jeanne C. Chambers⁷  Karen C. Short⁸ 

[1] Department of Forest, Rangeland, and Fire Sciences, University of Idaho, 875 Perimeter Drive MS 1135, 83844, Moscow, ID, USA;Department of Plant Sciences, University of California, Davis, One Shields Avenue, 95616, Davis, CA, USA;Fisheries, Wildlife, and Conservation Sciences Department, Oregon State University, 104 Nash Hall, Corvallis, OR, USA;U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, 97331, Corvallis, OR, USA;USDA Agricultural Research Service, 920 Valley Road, 89512, Reno, NV, USA;USDA Forest Service, Rocky Mountain Research Station, 800 East Beckwith Avenue, 59801, Missoula, MT, USA;USDA Forest Service, Rocky Mountain Research Station, 920 Valley Road, 89512, Reno, NV, USA;USDA Forest Service, Rocky Mountain Research Station, Highway 10 W, 5775, 59808, Missoula, MT, USA;

关键词: Artemisia tridentata;    Fuel Characteristic Classification System;    Fire modeling;    Fuel load;    Great Basin;    Juniperus occidentalis;    Juniperus osteosperma;    Pinyon-juniper woodland;    Pinus monophylla;    Sagebrush Steppe Treatment Evaluation Project;   

DOI  :  10.1186/s42408-023-00201-7

 received in 2023-02-10, accepted in 2023-06-14,  发布年份 2023

来源: Springer

【 摘 要 】

BackgroundNative pinyon (Pinus spp.) and juniper (Juniperus spp.) trees are expanding into shrubland communities across the Western United States. These trees often outcompete with native sagebrush (Artemisia spp.) associated species, resulting in increased canopy fuels and reduced surface fuels. Woodland expansion often results in longer fire return intervals with potential for high severity crown fire. Fuel treatments are commonly used to prevent continued tree infilling and growth and reduce fire risk, increase ecological resilience, improve forage quality and quantity, and/or improve wildlife habitat. Treatments may present a trade-off; they restore shrub and herbaceous cover and decrease risk of canopy fire but may increase surface fuel load and surface fire potential. We measured the accumulation of surface and canopy fuels over 10 years from ten sites across the Intermountain West in the Sagebrush Steppe Treatment Evaluation Project woodland network (www.SageSTEP.org), which received prescribed fire or mechanical (cut and drop) tree reduction treatments. We used the field data and the Fuel Characteristic Classification System (FCCS) in the Fuel and Fire Tools (FFT) application to estimate surface and canopy fire behavior in treated and control plots in tree expansion phases I, II, and III.ResultsIncreased herbaceous surface fuel following prescribed fire treatments increased the modeled rate of surface fire spread (ROS) 21-fold and nearly tripled flame length (FL) by year ten post-treatment across all expansion phases. In mechanical treatments, modeled ROS increased 15-fold, FL increased 3.8-fold, and reaction intensity roughly doubled in year ten post-treatment compared to pretreatment and untreated controls. Treatment effects were most pronounced at 97th percentile windspeeds, with modeled ROS up to 82 m min−1 in mechanical and 106 m min−1 in prescribed fire treatments by 10 years post-treatment compared to 5 m min−1 in untreated controls. Crown fire transmissivity risk was eliminated by both fuel treatments.ConclusionsWhile prescribed fire and mechanical treatments in shrublands experiencing tree expansion restored understory vegetation and prevented continued juniper and pinyon infilling and growth, these fuel treatments also increased modeled surface fire behavior. Thus, management tradeoffs occur between desired future vegetation and wildfire risk after fuel treatments.

【 授权许可】

CC BY   
© Association for Fire Ecology 2023

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