Examining Historical and Current Mixed-Severity Fire Regimes in Ponderosa Pine and Mixed-Conifer Forests of Western North America

Dry mixed-conifer forests are widespread in the interior Pacific Northwest, but their historical fire regimes are poorly characterized, in particular the relative mix of low- and high-severity fire. We reconstructed a multi-century history of fire from tree rings in dry mixed-conifer forests in central Oregon. These forests are dominated by ponderosa pine (Pinus ponderosa Lawson & C. Lawson), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), and grand fir (Abies grandis (Douglas ex D. Don) Lindl.). Across four, 30-plot grids of ∼800 ha covering a mosaic of dry mixed-conifer forest types, we sampled 4065 trees for evidence of both high- and low-severity fire. From 1650 to ∼1900, all four sites sustained frequent, often extensive, low-severity fires that sometimes included small patches of severe fire (50–150 ha during 18%–28% of fire years). Fire intervals were similar among sites and also among forest types within sites (mean intervals of 14–32 years). To characterize the continuous nature of the variation in fire severity, we computed a plot-based index that captures the relative occurrence of low- and high-severity fire. Our work contributes to the growing understanding of variation in past fire regimes in the complex and dynamic forests of North America’s Interior West.

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Californian mixed-conifer forests under unmanaged fire regimes in the Sierra San Pedro Martir, Baja California, Mexico

Journal of Biogeography ◽

10.1046/j.1365-2699.2000.00368.x ◽

2000 ◽

Vol 27 (1) ◽

pp. 105-129 ◽

Cited By ~ 95

Author(s):

R. A. Minnich ◽

M. G. Barbour ◽

J. H. Burk ◽

J. Sosa-Ramirez

Keyword(s):

Baja California ◽

Fire Regimes ◽

Conifer Forests ◽

Mixed Conifer ◽

San Pedro ◽

Mixed Conifer Forests ◽

Sierra San Pedro Martir

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Topographic variation in tree group and gap structure in Sierra Nevada mixed-conifer forests with active fire regimes

Forest Ecology and Management ◽

10.1016/j.foreco.2020.118220 ◽

2020 ◽

Vol 472 ◽

pp. 118220 ◽

Cited By ~ 2

Author(s):

Jan Ng ◽

Malcolm P. North ◽

Alec J. Arditti ◽

Monica R. Cooper ◽

James A. Lutz

Keyword(s):

Sierra Nevada ◽

Fire Regimes ◽

Conifer Forests ◽

Mixed Conifer ◽

Active Fire ◽

Mixed Conifer Forests ◽

Topographic Variation ◽

Tree Group ◽

Gap Structure

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Differentiating mixed- and high-severity fire regimes in mixed-conifer forests of the Canadian Cordillera

Forest Ecology and Management ◽

10.1016/j.foreco.2014.12.027 ◽

2015 ◽

Vol 341 ◽

pp. 45-58 ◽

Cited By ~ 22

Author(s):

Hélène M. Marcoux ◽

Lori D. Daniels ◽

Sarah E. Gergel ◽

Eric Da Silva ◽

Ze’ev Gedalof ◽

...

Keyword(s):

Fire Regimes ◽

Canadian Cordillera ◽

Conifer Forests ◽

Mixed Conifer ◽

High Severity ◽

Mixed Conifer Forests

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Fine-scale factors influence fire regimes in mixed-conifer forests on three high mountains in Mexico

International Journal of Wildland Fire ◽

10.1071/wf13214 ◽

2014 ◽

Vol 23 (7) ◽

pp. 959 ◽

Cited By ~ 6

Author(s):

Larissa L. Yocom ◽

Peter Z. Fulé ◽

Donald A. Falk ◽

Celia García-Domínguez ◽

Eladio Cornejo-Oviedo ◽

...

Keyword(s):

Fire History ◽

Fire Regime ◽

Fire Regimes ◽

Mountain Range ◽

Fire Occurrence ◽

Fine Scale ◽

Conifer Forests ◽

Mixed Conifer ◽

Scale Factors ◽

Mixed Conifer Forests

We investigated the influence of broad- v. fine-scale factors on fire in an unusual landscape suitable for distinguishing the drivers of fire synchrony. Our study was conducted in the Sierra Madre Oriental mountain range, in north-eastern Mexico. We worked in nine sites on three parallel mountains that receive nearly identical broad-scale climatic influence, but between which fires are unlikely to spread. We collected and cross dated samples from 357 fire-scarred trees in nine sites in high-elevation mixed-conifer forests and identified fire dates. We used Jaccard similarity analysis to evaluate synchrony among sites and quantified relationships between climate and fire occurrence. Fires were historically frequent (mean fire interval ranged from 8 to 16 years in all sites) and dates of fire exclusion ranged from 1887 to 1962. We found low fire synchrony among the three mountains, indicating a strong influence of fine-scale factors on fire occurrence. Fire regime attributes were similar across mountains despite the independence of fire dates. La Niña events were associated with fire over time, although not significantly since the 1830s. Our results highlight the importance of scale in describing fire regimes and suggest that we can use fire history to understand controls on complex ecosystem processes and patterns.

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The effects of burn entry and burn severity on ponderosa pine and mixed conifer forests in Grand Canyon National Park

International Journal of Wildland Fire ◽

10.1071/wf13111 ◽

2015 ◽

Vol 24 (4) ◽

pp. 495 ◽

Cited By ~ 11

Author(s):

Anna M. Higgins ◽

Kristen M. Waring ◽

Andrea E. Thode

Keyword(s):

Ponderosa Pine ◽

National Park ◽

Forest Type ◽

Grand Canyon ◽

Burn Severity ◽

Conifer Forests ◽

Mixed Conifer ◽

Grand Canyon National Park ◽

White Fir ◽

Mixed Conifer Forests

Over a century of fire exclusion in frequent-fire ponderosa pine and dry mixed conifer forests has resulted in increased tree densities, heavy surface fuel accumulations and an increase in late successional, fire-intolerant trees. Grand Canyon National Park uses prescribed fires and wildfires to reduce fire hazard and restore ecosystem processes. Research is needed to determine post-fire vegetation response thus enabling future forest succession predictions. Our study focussed on the effects of burn entry and burn severity on species composition and regeneration in two forest types: ponderosa pine with white fir encroachment and dry mixed conifer. We found no difference in tree composition and structure in a single, low-severity burn compared with unburned areas in the white fir encroachment forest type. We found no white fir seedlings or saplings in a second-entry, low-severity burn in the white fir encroachment forest type. Second-entry burns were effective in reducing white fir densities in the white fir encroachment forest type. There was significant aspen regeneration following high-severity fire in the dry mixed conifer forest type. This research suggests that repeated entries and an increase in burn severity may be necessary for prescribed fire or wildfire to be effective in meeting management objectives.

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