Are plant community responses to wildfire contingent upon historical disturbance regimes?

Miller, Jesse E. D.; Safford, Hugh D.

doi:10.1111/geb.13115

Cited by 39 publications

(69 citation statements)

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“…It is crucial that resource managers understand what factors lead to increases in fire severity over historical conditions so they can effectively utilize limited mitigation and prevention resources. Severe wildfires in areas adapted to largely low‐severity fire can cause substantial changes to the landscape in the short and long term that affect biodiversity, soil stability, water quality, carbon balance, timber production, and recreational and aesthetic values (Maestrini et al 2017, Underwood et al 2018, Dove et al 2020, Miller and Safford 2020). Until now, our understanding of the influence of recent drought‐ and insect‐induced tree mortality on subsequent wildfire severity in western North America has been almost exclusively limited to mesic forests historically adapted to relatively infrequent, mixed‐ or high‐severity wildfire (Hicke et al 2012, Kane et al 2017), but outcomes from those forests may not be directly applicable to drier forests intrinsically adapted to frequent, mostly low‐severity fire (Stephens et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Recent bark beetle outbreaks influence wildfire severity in mixed‐conifer forests of the Sierra Nevada, California, USA

Wayman

Safford

2021

Ecological Applications

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In temperate forests, elevated frequency of drought related disturbances will likely increase the incidence of interactions between disturbances such as bark beetle epidemics and wildfires. Our understanding of the influence of recent drought and insect-induced tree mortality on wildfire severity has largely lacked information from forests adapted to frequent fire. A recent unprecedented tree mortality event in California's Sierra Nevada provides an opportunity to examine this disturbance interaction in historically frequent-fire forests. Using field data collected within areas of recent tree mortality that subsequently burned in wildfire, we examined whether and under what conditions wildfire severity relates to severity of prefire tree mortality in Sierra Nevada mixed-conifer forests. We collected data on 180 plots within the 2015 Rough Fire and 2016 Cedar Fire footprints (California, USA). Our analyses identified prefire tree mortality as influential on all measures of wildfire severity (basal area killed by fire, RdNBR, and canopy torch) on the Cedar Fire, although it was less influential than fire weather (relative humidity). Prefire tree mortality was influential on two of three fire-severity measures on the Rough Fire, and was the most important predictor of basal area killed by fire; topographic position was influential on two metrics. On the Cedar Fire, the influence of prefire mortality on basal area killed by fire was greater under milder weather conditions. All measures of fire severity increased as prefire mortality increased up to prefire mortality levels of approximately 30-40%; further increases did not result in greater fire severity. The interacting disturbances shifted a pine-dominated system (Rough Fire) to a cedar-pine-fir system, while the pre-disturbance fir-cedar system (Cedar Fire) saw its dominant species unchanged. Managers of historically frequent-fire forests will benefit from utilizing this information when prioritizing fuels reduction treatments in areas of recent tree mortality, as it is the first empirical study to document a relationship between prefire mortality and subsequent wildfire severity in these systems. This study contributes to a growing body of evidence that the influence of prefire tree mortality on wildfire severity in temperate coniferous forests may depend on other conditions capable of driving extreme wildfire behavior, such as weather.

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Section: Introductionmentioning

confidence: 99%

Recent bark beetle outbreaks influence wildfire severity in mixed‐conifer forests of the Sierra Nevada, California, USA

Wayman

Safford

2021

Ecological Applications

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“…The combination of α and β produces γ, the total species diversity supported in the larger area-landscape diversity. Although myriad hypotheses have been proposed and tested regarding the relationship between fire and these three levels of diversity, generalizations have been elusive, which signals the need for further conceptual work and hypothesis testing for understanding the variety of ways in which fire influences diversity (Parr & Andersen, 2006;Anderson et al, 2014;Burkle et al, 2015;Kelly & Brotons, 2017;He et al, 2019;Miller & Safford, 2020). In this paper, we test key hypotheses on the impact of wildfire on woody plant diversity in a topographically complex mountain range.…”

Section: Introductionmentioning

confidence: 97%

“…Understanding spatial and temporal variation in the fire-diversity nexus is especially critical given the profound anthropogenic alterations of fire regimes across the Earth and their cascading impacts on ecosystems and species, including humans (Bowman et al, 2020;Coop et al, 2020). Ecologists have responded by intensifying their efforts to develop generalizations about species diversity and fire that address the challenges of a fierier world in the Anthropocene (e.g., Perry et al, 2011;Burkle et al, 2015;Enright et al, 2015;Pausas & Ribiero, 2017;He et al, 2019;Bowman et al, 2020;Coop et al, 2020;Miller & Safford, 2020) Whittaker (1970,1972) partitioned species diversity into three components: alpha diversity (α), beta diversity (β), and gamma diversity (γ). α is species diversity at a point in the landscape (i.e., a site), which itself can be decomposed into the number of species (richness) and the evenness of abundances among species.…”

Section: Introductionmentioning

confidence: 99%

Wildfire and topography drive woody plant diversity in a Sky Island mountain range in the Southwest USA

Barton

Poulos

2021

Preprint

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Aim: Drastic changes in fire regimes are altering plant communities, inspiring ecologists to better understand the relationship between fire and plant species diversity. We examined the impact of a 2011 megafire on woody plant species diversity in an arid mountain range in southern Arizona, USA. We tested recent fire-diversity hypotheses by addressing the impact of the fire severity, fire variability, historic fire regimes, and topography on diversity. Location: Chiricahua National Monument, Chiricahua Mountains, Arizona. USA., part of the Sky Islands of the US-Mexico borderlands. Taxon: Woody plant species. Methods: We sampled woody plant diversity in 138 plots before (2002-2003) and after (2017-2018) the 2011 Horseshoe Two Megafire in three vegetation types and across fire severity and topographic gradients. We calculated gamma, beta, and alpha diversity and examined changes over time in burned vs. unburned plots and the shapes of the relationships of diversity with fire severity and topography. Results: Alpha species richness declined and beta and gamma diversity increased in burned but not unburned plots. Fire-induced enhancement of gamma diversity was confined to low fire severity plots. Alpha diversity did not exhibit a clear continuous relationship with fire severity. Beta diversity was enhanced by fire severity variation among plots and increased with fire severity up to very high diversity, where it declined slightly. Main Conclusions: The results reject the intermediate disturbance hypothesis for alpha diversity but weakly support it for gamma diversity. Spatial variation in fire severity promoted variation among plant assemblages, supporting the pyrodiversity hypothesis. Long-term drought probably amplified fire-driven diversity changes. Despite the apparent benign impact of the fire on diversity, the replacement of two large conifer species with shrubs signals the potential loss of functional diversity, emphasizing the importance of intervention to direct the transition to a novel vegetation mosaic.

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“…Suppression of wildfire was the rule across North America for more than half of the 20th century (Pyne 2004) yet fire, including historical fire regimes, is a fundamental driver of diversity in many ecosystems (He et al 2019, Miller and Safford 2020). As our understanding of fire’s ecological role has grown, attitudes toward fire shifted so that, by the 1970s, prescribed burning was used in a number of lightning‐fire‐prone ecosystems (Abrahamson 1984a).…”

Section: Introductionmentioning

confidence: 99%

Lessons from four decades of monitoring vegetation and fire: maintaining diversity and resilience in Florida’s uplands

Abrahamson

Abrahamson²,

Keller

2021

Ecological Monographs

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Worldwide, humans are altering the fire regimes (fire-return intervals, severity, seasonality) of fire-prone ecosystems, fragmenting natural landscapes, and altering climates. Efforts to restore fire regimes in natural areas are usually guided by fire management plans (FMP) that rely on prescribed burning. Despite the common use of FMPs, limited efforts have gone to assessing vegetative and faunal responses. While some insights into responses to fire from short-term studies are available, there is less knowledge about FMP outcomes applied over multiple decades. Peninsular Florida hosts many fire-prone communities including globally threatened Florida scrub. We repeatedly sampled species composition and abundance during a 38-yr period at 11 upland stands including wet prairies, flatwoods, and Florida scrub (i.e., oak scrub, rosemary scrub, hickory scrub). A total of 22 fires impacted the stands with individual stands experiencing as few as 2 and up to 11 fires. There was no invasion of non-native plants following fires and stands showed remarkable ecological resilience with limited change in species composition and modest abundance shifts due to differential recovery rates. Importantly, ecological resilience was not eroded with repeated fire. Species richness, evenness, and diversity were significantly higher at the end vs. beginning of our study, suggesting that current fire regimes are within the range of those with which species evolved. While resprouting shrubs and trees persevered under a range of fire-return intervals, an obligate-seeding shrub was adversely impacted by fires more frequent than FMP-recommended intervals. Several lessons are apparent from our findings. Best practice should: use the full range of firereturn variation at evolutionarily appropriate intervals; utilize natural fire seasons to the extent possible; compare outcomes and modify prescriptions as necessary to meet FMP goals; give special consideration to burn units with embedded associations of widely differing fire regimes than principal associations in order to maintain diversity of both associations; and account for climate change in FMPs since fire behavior, frequency, and community responses to fire will likely change in the coming decades. Outcomes of FMPs must be carefully evaluated to ensure prescriptions are evolutionarily appropriate and to ameliorate the impacts of altered climates.

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Are plant community responses to wildfire contingent upon historical disturbance regimes?

Cited by 39 publications

References 93 publications

Recent bark beetle outbreaks influence wildfire severity in mixed‐conifer forests of the Sierra Nevada, California, USA

Recent bark beetle outbreaks influence wildfire severity in mixed‐conifer forests of the Sierra Nevada, California, USA

Wildfire and topography drive woody plant diversity in a Sky Island mountain range in the Southwest USA

Lessons from four decades of monitoring vegetation and fire: maintaining diversity and resilience in Florida’s uplands

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