Resprouting responses of Acacia shrubs in the Western Desert of Australia - fire severity, interval and season influence survival

2007 ◽  
Vol 16 (3) ◽  
pp. 317 ◽  
Author(s):  
Boyd R. Wright ◽  
Peter J. Clarke
Keyword(s):  
Functional Group ◽  
Fire Severity ◽  
Fire Regimes ◽  
Arid Ecosystems ◽  
Western Desert ◽  
Soil Heating ◽  
High Severity ◽  
Landscape Response ◽  
Negative Effect ◽  
Resprouting Ability

The hummock grasslands of arid Australia are fire-prone ecosystems in which the perennial woody plants mostly resprout after fire. The resprouting ability among these species is poorly understood in relation to environmental variation; consequently, little is known about the impacts that contemporary fire regimes are having on vegetation within these systems. We examined the resprouting ability of adults and juveniles of four widespread Acacia species (A. aneura, A. kempeana, A. maitlandii, A. melleodora) by experimentally testing the effects of fire severity, interval and season. We found that fire severity and season strongly affected survival, but the magnitude of the effects was variable among the species. Unexpectedly, a short fire interval of 2 years did not have a strong negative effect on resprouting of any species. Fire severity had variable effects among the four species, with those species with more deeply buried buds being more resilient to high-severity soil heating than those with shallow buds. Season of fire also strongly affected survival of some species, and we propose that seasonal variation in soil heating and soil moisture mediated these effects. The species by environment interactions we observed within one functional group (resprouters with a soil-stored seed bank) and in one genus suggest that modelling landscape response to fire regimes will be complex in these arid ecosystems. We predict, however, that the dominant resprouting acacias in hummock grasslands of central Australia are highly resilient to a range of fire regimes.

Older forests used by northern spotted owls functioned as fire refugia during large wildfires, 1987–2017

2021 ◽  
Author(s):  
Damon B Lesmeister ◽  
Raymond J. Davis ◽  
Stan G. Sovern ◽  
Zhiqiang Yang
Keyword(s):  
Fire Regime ◽  
Fire Severity ◽  
Weather Conditions ◽  
Fire Regimes ◽  
Bimodal Distribution ◽  
Relative Difference ◽  
Positive Trend ◽  
Forest Types ◽  
Spotted Owl ◽  
High Severity

Abstract Background The northern spotted owl (Strix occidentalis caurina) is an Endangered Species Act-listed subspecies that requires forests with old-growth characteristics for nesting. With climate change, large, severe wildfires are expected to be more common and an increasing threat to spotted owl persistence. Understanding fire severity patterns related to nesting forest can be valuable for forest management that supports conservation and recovery, especially if nesting forest functions as fire refugia (i.e., lower fire severity than surrounding landscape). We examined the relationship between fire severity and nesting forests in 472 large wildfires (> 200 ha) that occurred rangewide during 1987–2017. We mapped fire severities (unburned-low, moderate, high) within each fire using relative difference normalized burn ratios and quantified differences in severity between pre-fire nesting forest (edge and interior) and non-nesting forest. We also quantified these relationships within areas of three fire regimes (low severity, very frequent; mixed severity, frequent; high severity, infrequent). Results Averaged over all fires, the interior nesting forest burned at lower severity than edge or non-nesting forest. These relationships were consistent within the low severity, very frequent and mixed severity, frequent fire regime areas. All forest types burned at similar severity within the high severity, infrequent fire regime. During two of the most active wildfire years that also had the largest wildfires occurring in rare and extreme weather conditions, we found a bimodal distribution of fire severity in all forest types. In those years, a higher amount—and proportion—of all forest types burned at high severity. Over the duration of the study, we found a strong positive trend in the proportion of wildfires that burned at high severity in the non-nesting forests, but not in the two nesting forest types. Conclusions Under most wildfire conditions, the microclimate of interior patches of nesting forests likely mitigated fire severity and thus functioned as fire refugia. With changing climates, the future of interior forest as fire refugia is unknown, but trends suggest these older forests can dampen the effect of increased wildfire activity and thus an important component of landscape plans focused on fire resiliency.

scholarly journals Biological soil crust communities 12–16 years after wildfires in Idaho, USA

2017 ◽  
Author(s):  
Heather T. Root ◽  
John C. Brinda ◽  
E. Kyle Dodson
Keyword(s):  
Species Richness ◽  
Functional Groups ◽  
Fire Severity ◽  
Biological Soil Crust ◽  
Vascular Plant ◽  
Fire Regimes ◽  
Arid Ecosystems ◽  
Plant Functional Groups ◽  
Ecosystem Functions ◽  
Soil Crust

Abstract. Changing fire regimes in western North America may impact biological soil crust (BSC) communities that influence many ecosystem functions, such as soil stability and C and N cycling. However, longer-term effects of wildfire on BSC abundance, species richness, functional groups, and ecosystem functions after wildfire (i.e. BSC resilience) is still poorly understood. We sampled BSC lichen and bryophyte communities at four sites in Idaho, USA, within foothill steppe communities that included wildfires from 12 to 16 years old. We established six plots outside each burn perimeter and compared them with six plots of varying severity within each fire perimeter at each site. BSC cover was most strongly negatively impacted by wildfire at sites that had well-developed BSC communities in adjacent unburned plots. BSC species richness was estimated to be 65 % greater in unburned plots compared with burned plots. In contrast, there was no evidence that vascular plant functional groups or fire severity (as measured by satellite metrics dNBR or RdNBR) significantly affected longer-term BSC responses. Three BSC functional groups (squamulose lichens, vagrant lichens, and tall turf mosses) exhibited a significant decrease in abundance in burned areas relative to adjacent unburned areas. The decreases in BSC cover and richness along with decreased abundance of several functional groups suggest that wildfire can negatively impact ecosystem function in these semi-arid ecosystems for at least one to two decades. This is a concern given that increased fire frequency is predicted for the region due to exotic grass invasion and climate change.

Fire and False Brome: How Do Prescribed Fire and Invasive Brachypodium sylvaticum Affect Each Other?

2015 ◽  
Vol 8 (2) ◽  
pp. 122-130 ◽  
Author(s):  
Lauren P. Poulos ◽  
Bitty A. Roy
Keyword(s):  
Prescribed Fire ◽  
Fire Severity ◽  
Seedling Emergence ◽  
Fire Regimes ◽  
National Forest ◽  
Invasive Grass ◽  
Brachypodium Sylvaticum ◽  
High Severity ◽  
Forest Sites ◽  
Noxious Weed

Brachypodium sylvaticum, a shade-tolerant, forest dwelling, and aggressive invasive grass native to Eurasia, is a noxious weed in California, Oregon, and Washington. This species could cause ecosystem collapse by altering forest fire regimes. To examine interactions with fire, we divided two Willamette National Forest sites into eight units and randomly selected half for treatment with prescribed fire in spring 2011. We assessed the effect of B. sylvaticum on fire (severity and intensity) as well as the effect of fire on B. sylvaticum (cover, seedling emergence, and dispersal). We found that B. sylvaticum cover decreased fire severity but had no effect on intensity. Furthermore, fire severity influenced B. sylvaticum cover; in areas receiving low-severity fire, the grass increased from 21 ± 15.05 to 34 ± 15.81%, but in areas of high-severity fire, cover remained consistently around 0% (0 ± 0% cover in yr 1 to 0.2 5± 0.25% in yr 3). In the field, prescribed fire decreased seedling emergence by 32% compared to controls, but not in an associated greenhouse experiment. However, in the greenhouse, severely burned plots had zero emergence, compared to 0.29 ± 0.14 seedlings low-severity m−2 plot. Fire severity also influenced dispersal in the field; we monitored plots with < 0.5% cover B. sylvaticum initially; when these plots experienced low severity fire, they had greater B. sylvaticum cover (increasing 1,200%), suggesting increased dispersal with less severe fires. High-severity dispersal plots did not experience increased cover. High severity fires have the potential to control the grass, but low-severity fires will likely increase its cover.

Historical high-severity fire patches in mixed-conifer forests

2015 ◽  
Vol 45 (11) ◽  
pp. 1587-1596 ◽  
Author(s):  
Larissa L. Yocom-Kent ◽  
Peter Z. Fulé ◽  
Windy A. Bunn ◽  
Eric G. Gdula
Keyword(s):  
Fire Regime ◽  
Fire Severity ◽  
Grand Canyon ◽  
Fire Regimes ◽  
Tree Age ◽  
Mixed Conifer ◽  
Fire Scar ◽  
High Severity ◽  
The North ◽  
Mixed Conifer Forests

Two ends of the fire regime spectrum are a frequent low-intensity fire regime and an infrequent high-intensity fire regime, but intermediate fire regimes combine high- and low-severity fire over space and time. We used fire-scar and tree-age data to reconstruct fire regime attributes of mixed-conifer and aspen forests in the North Rim area of Grand Canyon National Park, with a goal of estimating patch sizes of historical high-severity fire and comparing them with modern patch sizes. We used three methods based on (i) aspen groves, (ii) even-aged stands, and (iii) inverse distance weighting, to estimate occurrence and patch sizes of historical high-severity fire. Evidence of high-severity fire was common in the 1800s, and high-severity fire years were associated with drought. High-severity fire patch sizes likely ranged from 10−1 to 102 ha. However, the forest is quite young, and we cannot rule out a historical large high-severity fire that could have reinitiated much of the 1400 ha study area. Fire scars, which are indicative of low-severity fire, were also common. Historical fire was likely heterogeneous across the landscape. Maintaining heterogeneity of fire severity, size, and frequency would promote heterogeneity of forest structure and composition and resilience to future disturbances.

Mixed-severity fire regimes in dry forests of southern interior British Columbia, Canada

2012 ◽  
Vol 42 (1) ◽  
pp. 88-98 ◽  
Author(s):  
Emily K. Heyerdahl ◽  
Ken Lertzman ◽  
Carmen M. Wong
Keyword(s):  
British Columbia ◽  
Ponderosa Pine ◽  
Fire Regime ◽  
Fire Severity ◽  
Fire Regimes ◽  
Douglas Fir ◽  
Dry Forests ◽  
Ponderosa Pine Forests ◽  
Fire Scar ◽  
High Severity

Historical fire severity is poorly characterized for dry forests in the interior west of North America. We inferred a multicentury history of fire severity from tree rings in Douglas-fir ( Pseudotsuga menziesii var. glauca (Beissn.) Franco) – ponderosa pine ( Pinus ponderosa Douglas ex P. Lawson & C. Lawson) forests in the southern interior of British Columbia, Canada. In 2 ha plots distributed systematically over 1105 ha, we determined the dates of fire scars, indicators of low-severity fire, from 125 trees and inferred dates of even-aged cohorts, potential indicators of high-severity fire, from establishment dates of 1270 trees. Most (76%) of the 41 plots contained fire-scarred trees with a mean plot-composite fire scar interval of 21 years (1700–1900). Most (76%) also contained one or two cohorts. At the plot scale, we inferred that the fire regime at most plots was of mixed severity through time (66%) and at the remaining plots of low (20%), high (10%), or unknown (4%) severity through time. We suggest that across our study area, the fire regime was mixed severity over the past several centuries, with low-severity fires most common and often extensive but small, high-severity disturbances also occasionally occurred. Our results present strong evidence for the importance of mixed-severity fire regimes in which low-severity fires dominate in interior Douglas-fir – ponderosa pine forests in western Canada.

Fire severity alters spatio–temporal movements and habitat utilisation by an arboreal marsupial, the mountain brushtail possum (Trichosurus cunninghami)

2016 ◽  
Vol 25 (12) ◽  
pp. 1291 ◽  
Author(s):  
L. E. Berry ◽  
D. B. Lindenmayer ◽  
T. E. Dennis ◽  
D. A. Driscoll ◽  
S. C. Banks
Keyword(s):  
Fire Severity ◽  
Fire Regimes ◽  
Spatial And Temporal Variation ◽  
Brushtail Possum ◽  
Suitable Habitat ◽  
Spatial And Temporal Patterns ◽  
Salvage Logging ◽  
High Severity ◽  
Spatio Temporal ◽  
Surrounding Landscape

Understanding how severe wildfires influence faunal movement is essential for predicting how changes in fire regimes will affect ecosystems. We examined the effects of fire severity distribution on spatial and temporal variation in movement of an Australian arboreal mammal, the mountain brushtail possum (Trichosurus cunninghami). We used GPS telemetry to characterise the movements of 18 possums in landscapes burnt to differing extents by a large wildfire. We identified a temporal change in movement patterns in response to fire. In unburnt landscapes, individuals moved greater distances early and late in the night and had less overlap in the areas used for foraging and denning, than in high-severity burnt landscapes. Habitat selection was dependent on the spatial context of fire in the surrounding landscape. Forest recently burnt at high severity may provide suitable habitat for species such as the mountain brushtail possum, if protected from subsequent disturbance, such as salvage logging. However, spatial and temporal patterns of habitat use and selection differ considerably between burnt and undisturbed landscapes. The spatial outcomes of ecological disturbances such as wildfires have the potential to alter the behaviour and functional roles of fauna across large areas.

scholarly journals Is fire severity increasing in the Sierra Nevada, California, USA?

2014 ◽  
Vol 23 (1) ◽  
pp. 1 ◽  
Author(s):  
Chad T. Hanson ◽  
Dennis C. Odion
Keyword(s):  
Climate Change ◽  
Sierra Nevada ◽  
Fire Suppression ◽  
Biological Effects ◽  
Fire Severity ◽  
Fire Regimes ◽  
High Severity ◽  
Current Trends ◽  
In Fire ◽  
Fire Extent

Research in the Sierra Nevada range of California, USA, has provided conflicting results about current trends of high-severity fire. Previous studies have used only a portion of available fire severity data, or considered only a portion of the Sierra Nevada. Our goal was to investigate whether a trend in fire severity is occurring in Sierra Nevada conifer forests currently, using satellite imagery. We analysed all available fire severity data, 1984–2010, over the whole ecoregion and found no trend in proportion, area or patch size of high-severity fire. The rate of high-severity fire has been lower since 1984 than the estimated historical rate. Responses of fire behaviour to climate change and fire suppression may be more complex than assumed. A better understanding of spatiotemporal patterns in fire regimes is needed to predict future fire regimes and their biological effects. Mechanisms underlying the lack of an expected climate- and time since fire-related trend in high-severity fire need to be identified to help calibrate projections of future fire. The effects of climate change on high-severity fire extent may remain small compared with fire suppression. Management could shift from a focus on reducing extent or severity of fire in wildlands to protecting human communities from fire.

A multi-century history of fire regimes along a transect of mixed-conifer forests in central Oregon, U.S.A.

2019 ◽  
Vol 49 (1) ◽  
pp. 76-86 ◽  
Author(s):  
Emily K. Heyerdahl ◽  
Rachel A. Loehman ◽  
Donald A. Falk
Keyword(s):  
Pinus Ponderosa ◽  
Ponderosa Pine ◽  
Fire Severity ◽  
Fire Regimes ◽  
Conifer Forests ◽  
Forest Types ◽  
Mixed Conifer ◽  
High Severity ◽  
Mixed Conifer Forests ◽  
History Of

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.

scholarly journals Northern spotted owl nesting forests as fire refugia: a 30-year synthesis of large wildfires

Fire Ecology ◽  
2021 ◽  
Vol 17 (1) ◽  
Author(s):  
Damon B. Lesmeister ◽  
Raymond J. Davis ◽  
Stan G. Sovern ◽  
Zhiqiang Yang
Keyword(s):  
Fire Regime ◽  
Fire Severity ◽  
Weather Conditions ◽  
Fire Regimes ◽  
Positive Trend ◽  
Forest Types ◽  
Spotted Owl ◽  
High Severity ◽  
Northern Spotted Owl ◽  
Lower Severity

Abstract Background The northern spotted owl (Strix occidentalis caurina) is an Endangered Species Act-listed subspecies that requires coniferous forests with structurally complex and closed-canopy old-growth characteristics for nesting. With climate change, large wildfires are expected to become more common within the subspecies’ range and an increasing threat to these types of forests. Understanding fire severity patterns related to suitable nesting forest will be important to inform forest management that affects conservation and recovery. We examined the relationship between fire severity and suitable nesting forest in 472 large wildfires (> 200 ha) that occurred in the northern spotted owl range during 1987–2017. We mapped fire severities (unburned-low, moderate, high) within each fire using relative differenced normalized burn ratios and quantified differences in severity between pre-fire suitable nesting forest (edge and interior) and non-nesting forest. We also quantified these relationships within areas of three fire regimes (low severity, very frequent; mixed severity, frequent; high severity, infrequent). Results Averaged over all fires, the interior nesting forest burned at lower severity than edge or non-nesting forest. These relationships were consistent within the low severity, very frequent, and mixed severity, frequent fire regime areas. All forest types burned at similar severity within the high severity, infrequent fire regime. During two of the most active wildfire years that also had the largest wildfires occurring in rare and extreme weather conditions, we found a bimodal distribution of fire severity in all forest types. In those years, a higher amount—and proportion—of all forest types burned at high severity. Over the 30-year study, we found a strong positive trend in the proportion of wildfires that burned at high severity in the non-nesting forests, but not in the suitable nesting forest types. Conclusions Under most wildfire conditions, the microclimate of interior patches of suitable nesting forests likely mitigated fire severity and thus functioned as fire refugia (i.e., burning at lower severity than the surrounding landscape). With changing climate, the future of interior forest as fire refugia is unknown, but trends suggest older forests can dampen the effect of increased wildfire activity and be an important component of landscapes with fire resiliency.

scholarly journals High-severity wildfires in temperate Australian forests have increased in extent and aggregation in recent decades

PLoS ONE ◽  
2020 ◽  
Vol 15 (11) ◽  
pp. e0242484
Author(s):  
Bang Nguyen Tran ◽  
Mihai A. Tanase ◽  
Lauren T. Bennett ◽  
Cristina Aponte
Keyword(s):  
Fire Regime ◽  
Fire Severity ◽  
Fire Regimes ◽  
Ecosystem Dynamics ◽  
Burned Area ◽  
Burned Areas ◽  
South Eastern ◽  
High Severity ◽  
Eastern Australia ◽  
South Eastern Australia

Wildfires have increased in size and frequency in recent decades in many biomes, but have they also become more severe? This question remains under-examined despite fire severity being a critical aspect of fire regimes that indicates fire impacts on ecosystem attributes and associated post-fire recovery. We conducted a retrospective analysis of wildfires larger than 1000 ha in south-eastern Australia to examine the extent and spatial pattern of high-severity burned areas between 1987 and 2017. High-severity maps were generated from Landsat remote sensing imagery. Total and proportional high-severity burned area increased through time. The number of high-severity patches per year remained unchanged but variability in patch size increased, and patches became more aggregated and more irregular in shape. Our results confirm that wildfires in southern Australia have become more severe. This shift in fire regime may have critical consequences for ecosystem dynamics, as fire-adapted temperate forests are more likely to be burned at high severities relative to historical ranges, a trend that seems set to continue under projections of a hotter, drier climate in south-eastern Australia.

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