Resilience of Oregon white oak to reintroduction of fire

Nemens, Deborah G.; Varner, J. Morgan; Dunwiddie, Peter W.

doi:10.1186/s42408-019-0045-9

Cited by 7 publications

(5 citation statements)

References 46 publications

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“…Although Q. garryana is considered a fire endurer, it exhibits both endurer and resister traits. Seedlings have deep taproots that allow for resprouting following fire and mature adults can have thick fire‐resistant bark (Agee, 1993; Nemens et al, 2019). Quercus garryana seedlings are also often found on frequently disturbed sites along with other early successional taxa (Agee, 1993).…”

Section: Discussionmentioning

confidence: 99%

“…Quercus garryana seedlings are also often found on frequently disturbed sites along with other early successional taxa (Agee, 1993). These adaptations allow Q. garryana to outcompete many other woody species in environments with frequent low‐severity fire, particularly P. menziesii (Nemens et al, 2019; Sprenger & Dunwiddie, 2011). Therefore, Q. garryana and its associated savanna communities on Pender Island would have benefitted from frequent low‐severity fire by hindering P. menziesii encroachment.…”

Section: Discussionmentioning

confidence: 99%

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Holocene fire regimes, fire‐related plant functional types, and climate in south‐coastal British Columbia forests

Giuliano

Lacourse

2023

Ecosphere

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Paleoecological records of past fire events and forest composition provide long‐term ecological context for modern changes in fire regimes and forest dynamics. Here, we use pollen and contiguous macroscopic charcoal analyses of lake sediments from Pender Island, British Columbia, Canada to reconstruct changes in fire regimes over the last 10,000 years and investigate how these interact with changes in climate and forest composition with a focus on fire‐related plant functional types. The relatively warm and dry early Holocene was characterized by high charcoal accumulation rates, fire episodes of moderate severity, and a mean fire return interval of 100 ± 27 years. Forests at the time were open‐canopy Pseudotsuga menziesii forests with abundant fire endurer taxa (e.g., Pteridium aquilinum) that have a competitive advantage in regimes of frequent fire. Fire continued to occur every ~100 years, on average, during the establishment of Quercus garryana savanna communities; however, a decrease in charcoal peak magnitudes suggests the fire regime shifted to one characterized by smaller and/or lower intensity surface fires. As temperature and moisture deficits decreased in the mid‐ and late Holocene (i.e., after ~6000 calendar years before present), mean fire return intervals lengthened to 176 ± 54 years and increased variability in charcoal peak magnitudes suggests a mixed fire regime of low‐moderate‐intensity fires combined with infrequent crown or stand‐replacing fires. Relatively stable and moderate climate, longer fire return intervals, and mixed‐severity fires allowed P. menziesii (a fire resister) to dominate closed‐canopy forests and for fire avoiders to gradually become more common forest constituents. Millennial‐scale climate change has acted as the dominant driver of changes in both fire regimes and forest composition over the last 10,000 years; however, changes in fire‐related plant functional types highlight the important role that interactions between vegetation and fire play in long‐term fire regimes and forest dynamics.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Holocene fire regimes, fire‐related plant functional types, and climate in south‐coastal British Columbia forests

Giuliano

Lacourse

2023

Ecosphere

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“…Both species are typical resprouters (Cruz et al 2003;Reyes et al 2009), so they have storage organs from which carbohydrate and nutrient reserves are mobilized after fire in order to regenerate vegetatively Clarke et al 2013). Thus, many authors have highlighted resprouting as a reproductive strategy that facilitates the post-fire regeneration capacity of vegetation (Calvo et al 1998;Calvo et al 2002aCalvo et al , 2002cLamont et al 2011), as well as a good strategy to face severe disturbances (Clarke et al 2013;Fernández-García et al 2020;Huerta et al 2021) and promote resilience (Nemens et al 2019;Menges et al 2021). In such a way, E. australis is able to resprout quickly after fire, but interspecific competition may affect its recovery (Calvo et al 1998).…”

Section: Discussionmentioning

confidence: 99%

Resilience of Mediterranean communities to fire depends on burn severity and type of ecosystem

et al. 2022

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Background Burn severity plays an important role in shaping vegetation recovery in Mediterranean ecosystems. In the present study, we aimed to evaluate the influence of burn severity on short-term vegetation resilience in different ecosystems. We selected the Cabrera wildfire (northwest Iberian Peninsula), which affected shrubland, heathland, broomland, and oak woodland ecosystems in 2017. Immediately after the fire, we established 249 field plots within the burned area, in which burn severity was quantified by the application of the Composite Burn Index, differentiating three burn severity categories: low, moderate, and high. Moreover, we fixed 136 plots in unburned areas at two different maturity stages: young (unburned for the last 10 years) and old (unburned for the last 20 years) vegetation. Two years after the wildfire, we evaluated the total percentage cover of vegetation in four vertical strata ranging from 0 to > 4 m, as well as the cover of each woody species and total herbaceous vegetation in the lowest stratum (0–0.5 m). Resilience of the 2017 burned areas was interpreted in terms of the difference in vegetation cover and species composition in relation to the two different maturity stages. Results The results showed that the lowest stratum was the most resilient in the short term. In fact, all ecosystems presented high resilience of this stratum in low-severity areas. In shrublands and heathlands, this was mainly the consequence of the regeneration of herbaceous vegetation, as the dominant woody species did not fully recover in any of the burned situations (at least 21% and 11% less cover in shrubland and heathland burned plots compared to areas of young vegetation). Specifically, the resilience of this stratum was higher in broomlands and oak woodlands, mainly under moderate and high severities. In these ecosystems, woody dominant species recovered with respect to young vegetation at the 0–0.5-m level. Despite this, burn severity had a negative impact on the short-term resilience of the uppermost strata in broomlands and oak woodlands (cover values close to 0%). Conclusions The effects of burn severity on short-term vegetation resilience differed among type of ecosystems and vertical strata, so these results may constitute a starting point for the evaluation of the influence of burn severity and vegetation composition and structure on ecosystem resilience.

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“…Bole injury is another common predictor variable used in post‐fire tree mortality models, acting as an indicator of cambial injury (Beverly & Martell, 2003; Hood et al, 2008; Thies et al, 2006). Metrics of bole injury include the height of charring, proportion of circumference/height charred, and measures of depth or severity of charring (Hood et al, 2018; Nemens et al, 2019). The use of bark charring as a metric of injury has received some criticism, since this external measure fails to encompass underlying injury to vascular cambia, especially for thick barked species (Hood et al, 2018) and more often, charring is simply an indicator of flaming zone heating and fire spread direction.…”

Section: Introductionmentioning

confidence: 99%

Predictive accuracy of post‐fire conifer death declines over time in models based on crown and bole injury

Shearman

Varner

Hood

et al. 2022

Ecological Applications

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A key uncertainty of empirical models of post‐fire tree mortality is understanding the drivers of elevated post‐fire mortality several years following fire, known as delayed mortality. Delayed mortality can represent a substantial fraction of mortality, particularly for large trees that are a conservation focus in western US coniferous forests. Current post‐fire tree mortality models have undergone limited evaluation of how injury level and time since fire interact to influence model accuracy and predictor variable importance. Less severe injuries potentially serve as an indicator for vulnerability to additional stressors such as bark beetle attack or moisture stress. We used a collection of 164,293 individual tree records to examine post‐fire tree mortality in eight western USA conifers: Abies concolor, Abies grandis, Calocedrus decurrens, Larix occidentalis, Pinus contorta, Pinus lambertiana, Pinus ponderosa, and Pseudotsuga menziesii. We evaluated the importance of fire injury predictors on discriminating between surviving trees versus immediate and delayed post‐fire mortality. We fit balanced random forest models for each species using cumulative tree mortality from 1 to 5‐years post‐fire. We compared these results to multi‐class random forest models using first‐year mortality, 2–5‐year mortality, and survival 5‐years post‐fire as a response variable. Crown volume scorched, diameter at breast height, and relative bark char height, were used as predictor variables. The cumulative mortality models all predicted trees that died within 1‐year of fire with high accuracy but failed to predict 2–5‐year mortality. The multi‐class models were an improvement but had lower accuracy for predicting 2–5‐year mortality. Multi‐class model accuracies ranged from 85% to 95% across all species for predicting 1‐year post‐fire mortality, 42%–71% for predicting 2–5‐year mortality, and 64%–85% for predicting trees that lived past 5‐years. Our study highlights the differences in tree species tolerance to fire injury and suggests that including second‐order predictors such as beetle attack or climatic water stress before and after fire will be critical to improve accuracy and better understand the mechanisms and patterns of fire‐caused tree death. Random forest models have potential for management applications such as post‐fire harvesting and simulating future stand dynamics.

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Resilience of Oregon white oak to reintroduction of fire

Cited by 7 publications

References 46 publications

Holocene fire regimes, fire‐related plant functional types, and climate in south‐coastal British Columbia forests

Holocene fire regimes, fire‐related plant functional types, and climate in south‐coastal British Columbia forests

Resilience of Mediterranean communities to fire depends on burn severity and type of ecosystem

Predictive accuracy of post‐fire conifer death declines over time in models based on crown and bole injury

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