Mortality and recruitment of fire-tolerant eucalypts as influenced by wildfire severity and recent prescribed fire

Bennett, Lauren T.; Bruce, Matthew; MacHunter, Josephine; Kohout, Michele; Tanase, Mihai A.; Aponte, Cristina

doi:10.1016/j.foreco.2016.08.047

Cited by 94 publications

(97 citation statements)

References 68 publications

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“…Our study, combined with recent evidence of increased mortality of resprouter eucalypts after single high‐severity wildfires (Bennett et al. ; Fairman et al. ; Prior et al.…”

Section: Discussionsupporting

confidence: 75%

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Frequent wildfires erode tree persistence and alter stand structure and initial composition of a fire‐tolerant sub‐alpine forest

Fairman

Bennett

Tupper

et al. 2017

J Vegetation Science

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Question Frequent severe wildfires have the potential to alter the structure and composition of forests in temperate biomes. While temperate forests dominated by resprouting trees are thought to be largely invulnerable to more frequent wildfires, empirical data to support this assumption are lacking. Does frequent fire erode tree persistence by increasing mortality and reducing regeneration, and what are the broader impacts on forest structure and understorey composition? Location Sub‐alpine open Eucalyptus pauciflora forests, Australian Alps, Victoria, Australia. Methods We examined tree persistence and understorey composition of E. pauciflora open forests that were unburned, burned once, twice or three times by high‐severity wildfires between 2003 and 2013. At each of 20 sites (five per fire frequency class) we assessed extent of top‐kill and mortality of eucalypt clumps, spatial configuration of surviving and dead clumps, densities of new and lignotuberous eucalypt seedlings, and shrub and grass cover. Results At least 2 yr after the last wildfire, proportions of top‐killed E. pauciflora stems were significantly higher, and densities of live basal resprouts significantly lower, at sites burned two or three times compared to once burned or unburned sites. Clump death increased to 50% of individuals at sites burned by three short‐interval wildfires, which led to changes in live tree patchiness, as indicated by nearest‐neighbour indices. Increased tree mortality was not offset by seedling recruitment, which was significantly lower at the twice‐ and thrice‐burned sites relative to single‐burn sites – although seedling recruitment was also influenced by topography and coarse woody debris. In addition to changes in the tree layer, the prominence of understorey shrubs was substantially reduced, and the frequency of grasses markedly increased, after two, and particularly three wildfires. Conclusions Our study provides strong empirical evidence of ecologically significant change in E. pauciflora forests after short‐interval severe wildfires, namely, erosion of the persistence niche of resprouting trees, and a shift in understorey dominance from shrubs to grasses. Our findings highlight the need to consider the impacts of compounded perturbation on forests under changing climates, including testing assumptions of long‐term persistence of resprouter‐dominated communities.

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“…Our study, combined with recent evidence of increased mortality of resprouter eucalypts after single high‐severity wildfires (Bennett et al. ; Fairman et al. ; Prior et al.…”

Section: Discussionsupporting

confidence: 75%

“…Recent studies have indicated increased mortality of fire‐tolerant resprouting trees under extreme fire conditions (Bennett et al. ; Prior et al. ; Nicholson et al.…”

Section: Introductionmentioning

confidence: 99%

Frequent wildfires erode tree persistence and alter stand structure and initial composition of a fire‐tolerant sub‐alpine forest

Fairman

Bennett

Tupper

et al. 2017

J Vegetation Science

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“…The forest type, known locally as “Herb‐rich Foothill Forest” (Department of Sustainability and Environment ), is a dry sclerophyll forest (Ashton ) or “open forest” (tree heights 10–30 m, projective foliage cover 30–70%; Specht ) of mean basal area 29 m 2 /ha (Bennett et al. ). It is dominated by a mix of fire‐tolerant eucalypts of different bark types, such as Eucalyptus obliqua L'Hér (deep fibrous “stringybark”), E. radiata Sieber ex DC.…”

Section: Methodsmentioning

confidence: 99%

“…However, empirical data to assess the carbon stability of many fire‐tolerant forests are lacking; in particular, few studies have assessed wildfire effects on carbon stocks in fire‐tolerant eucalypt forests despite evidence of increased mortalities of fire‐tolerant eucalypts (and, thus, potential for decreased biomass carbon) after recent high‐intensity wildfires in south‐eastern Australia (Bennett et al. , Prior et al. ).…”

Section: Introductionmentioning

confidence: 99%

Assessing fire impacts on the carbon stability of fire‐tolerant forests

Bennett

Bruce

MacHunter

et al. 2017

Ecological Applications

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The carbon stability of fire-tolerant forests is often assumed but less frequently assessed, limiting the potential to anticipate threats to forest carbon posed by predicted increases in forest fire activity. Assessing the carbon stability of fire-tolerant forests requires multi-indicator approaches that recognize the myriad ways that fires influence the carbon balance, including combustion, deposition of pyrogenic material, and tree death, post-fire decomposition, recruitment, and growth. Five years after a large-scale wildfire in southeastern Australia, we assessed the impacts of low- and high-severity wildfire, with and without prescribed fire (≤10 yr before), on carbon stocks in multiple pools, and on carbon stability indicators (carbon stock percentages in live trees and in small trees, and carbon stocks in char and fuels) in fire-tolerant eucalypt forests. Relative to unburned forest, high-severity wildfire decreased short-term (five-year) carbon stability by significantly decreasing live tree carbon stocks and percentage stocks in live standing trees (reflecting elevated tree mortality), by increasing the percentage of live tree carbon in small trees (those vulnerable to the next fire), and by potentially increasing the probability of another fire through increased elevated fine fuel loads. In contrast, low-severity wildfire enhanced carbon stability by having negligible effects on aboveground stocks and indicators, and by significantly increasing carbon stocks in char and, in particular, soils, indicating pyrogenic carbon accumulation. Overall, recent preceding prescribed fire did not markedly influence wildfire effects on short-term carbon stability at stand scales. Despite wide confidence intervals around mean stock differences, indicating uncertainty about the magnitude of fire effects in these natural forests, our assessment highlights the need for active management of carbon assets in fire-tolerant eucalypt forests under contemporary fire regimes. Decreased live tree carbon and increased reliance on younger cohorts for carbon recovery after high-severity wildfire could increase vulnerabilities to imminent fires, leading to decisions about interventions to maintain the productivity of some stands. Our multi-indicator assessment also highlights the importance of considering all carbon pools, particularly pyrogenic reservoirs like soils, when evaluating the potential for prescribed fire regimes to mitigate the carbon costs of wildfires in fire-prone landscapes.

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“…It is especially prevalent through the recent increase in human-induced landscape transformation and rapid climate change, especially in Mediterranean-type ecosystems, where warmer and drier conditions are increasingly prevalent (Archibald, Staver, & Levin, 2012;Bowman et al, 2011;Steel, Safford, & Viers, 2015;Syphard, Radeloff, Hawbaker, & Stewart, 2009). The immediate impact of fire usually results in high mortality of resident species, which increases with intensity and frequency of the fire (Adeney, Ginsberg, Russell, & Kinnaird, 2006;Bennett et al, 2016;Silveira, Barlow, Louzada, & Moutinho, 2010). Flower-visiting insects, especially the less mobile species, are greatly affected by fire in natural landscapes.…”

Section: Introductionmentioning

confidence: 99%

Refuges from fire maintain pollinator–plant interaction networks

Adedoja

Dormann

Kehinde

et al. 2019

Ecology and Evolution

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Fire is a major disturbance factor in many terrestrial ecosystems, leading to landscape transformation in fire‐prone areas. Species in mutualistic interactions are often highly sensitive to disturbances like fire events, but the degree and complexity of their responses are unclear. We use bipartite insect–flower interaction networks across a recently burned landscape to explore how plant–pollinator interaction networks respond to a recent major fire event at the landscape level, and where fire refuges were present. We also investigate the effectiveness of these refuges at different elevations (valley to hilltop) for the conservation of displaced flower‐visiting insects during fire events. Then, we explore how the degree of specialization of flower‐visiting insects changes across habitats with different levels of fire impact. We did this in natural areas in the Greater Cape Floristic Region (GCFR) biodiversity hotspot, which is species rich in plants and pollinators. Bees and beetles were the most frequent pollinators in interactions, followed by wasps and flies. Highest interaction activity was in the fire refuges and least in burned areas. Interactions also tracked flower abundance, which was highest in fire refuges in the valley and lowest in burned areas. Interactions consisted mostly of specialized flower visitors, especially in refuge areas. The interaction network and species specialization were lowest in burned areas. However, species common to at least two fire classes showed no significant difference in species specialization. We conclude that flower‐rich fire refuges sustain plant–pollinator interactions, especially those involving specialized species, in fire‐disturbed landscape. This may be an important shelter for specialized pollinator species at the time that the burned landscape goes through regrowth and succession as part of ecosystem recovery process after a major fire event.

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Mortality and recruitment of fire-tolerant eucalypts as influenced by wildfire severity and recent prescribed fire

Cited by 94 publications

References 68 publications

Frequent wildfires erode tree persistence and alter stand structure and initial composition of a fire‐tolerant sub‐alpine forest

Frequent wildfires erode tree persistence and alter stand structure and initial composition of a fire‐tolerant sub‐alpine forest

Assessing fire impacts on the carbon stability of fire‐tolerant forests

Refuges from fire maintain pollinator–plant interaction networks

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