scholarly journals Resilience of the boreal forest in response to Holocene fire-frequency changes assessed by pollen diversity and population dynamics

2010 ◽  
Vol 19 (8) ◽  
pp. 1026 ◽  
Author(s):  
Christopher Carcaillet ◽  
Pierre J. H. Richard ◽  
Yves Bergeron ◽  
Bianca Fréchette ◽  
Adam A. Ali
Keyword(s):  
Boreal Forest ◽  
Boreal Forests ◽  
Frequency Control ◽  
Regional Scale ◽  
Fire Regimes ◽  
Fire Frequency ◽  
Frequency Changes ◽  
Fire Intervals ◽  
In Fire

The hypothesis that changes in fire frequency control the long-term dynamics of boreal forests is tested on the basis of paleodata. Sites with different wildfire histories at the regional scale should exhibit different vegetation trajectories. Mean fire intervals and vegetation reconstructions are based respectively on sedimentary charcoal and pollen from two small lakes, one in the Mixedwood boreal forests and the second in the Coniferous boreal forests. The pollen-inferred vegetation exhibits different trajectories of boreal forest dynamics after afforestation, whereas mean fire intervals have no significant or a delayed impact on the pollen data, either in terms of diversity or trajectories. These boreal forests appear resilient to changes in fire regimes, although subtle modifications can be highlighted. Vegetation compositions have converged during the last 1200 years with the decrease in mean fire intervals, owing to an increasing abundance of boreal species at the southern site (Mixedwood), whereas changes are less pronounced at the northern site (Coniferous). Although wildfire is a natural property of boreal ecosystems, this study does not support the hypothesis that changes in mean fire intervals are the key process controlling long-term vegetation transformation. Fluctuations in mean fire intervals alone do not explain the historical and current distribution of vegetation, but they may have accelerated the climatic process of borealisation, likely resulting from orbital forcing.

scholarly journals Altered fire regimes modify lizard communities in globally endangered Araucaria forests of the southern Andes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
José Infante ◽  
Fernando J. Novoa ◽  
José Tomás Ibarra ◽  
Don J. Melnick ◽  
Kevin L. Griffin ◽  
...  
Keyword(s):  
Habitat Structure ◽  
Distance Sampling ◽  
Fire Regimes ◽  
Fire Frequency ◽  
Old Growth ◽  
Southern Andes ◽  
Habitat Features ◽  
Araucaria Araucana ◽  
In Fire

AbstractWildfire regimes are being altered in ecosystems worldwide. The density of reptiles responds to fires and changes to habitat structure. Some of the most vulnerable ecosystems to human-increased fire frequency are old-growth Araucaria araucana forests of the southern Andes. We investigated the effects of wildfires on the density and richness of a lizard community in these ecosystems, considering fire frequency and elapsed time since last fire. During the 2018/2019 southern summer season, we conducted 71 distance sampling transects to detect lizards in Araucaria forests of Chile in four fire “treatments”: (1) unburned control, (2) long-term recovery, (3) short-term recovery, and (4) burned twice. We detected 713 lizards from 7 species. We found that the density and richness of lizards are impacted by wildfire frequency and time of recovery, mediated by the modification of habitat structure. The lizard community varied from a dominant arboreal species (L. pictus) in unburned and long-recovered stands, to a combination of ground-dwelling species (L. lemniscatus and L. araucaniensis) in areas affected by two fires. Araucaria forests provided key habitat features to forest reptiles after fires, but the persistence of these old-growth forests and associated biodiversity may be threatened given the increase in fire frequency.

Assessing accuracy of point fire intervals across landscapes with simulation modelling

2007 ◽  
Vol 37 (9) ◽  
pp. 1605-1614 ◽  
Author(s):  
Russell A. Parsons ◽  
Emily K. Heyerdahl ◽  
Robert E. Keane ◽  
Brigitte Dorner ◽  
Joseph Fall
Keyword(s):  
Fire Regime ◽  
Fire Regimes ◽  
Maximum Error ◽  
Simulation Modelling ◽  
Fire Frequency ◽  
Spatially Explicit ◽  
Forest Types ◽  
Fire Scar ◽  
Fire Intervals ◽  
In Fire

We assessed accuracy in point fire intervals using a simulation model that sampled four spatially explicit simulated fire histories. These histories varied in fire frequency and size and were simulated on a flat landscape with two forest types (dry versus mesic). We used three sampling designs (random, systematic grids, and stratified). We assessed the sensitivity of estimates of Weibull median probability fire intervals (WMPI) to sampling design and to factors that degrade the fire scar record: failure of a tree to record a fire and loss of fire-scarred trees. Accuracy was affected by all of the factors investigated and generally varied with fire regime type. The maximum error was from degradation of the record, primarily because degradation reduced the number of intervals from which WMPI was estimated. The sampling designs were roughly equal in their ability to capture overall WMPI, regardless of fire regime, but the gridded design yielded more accurate estimates of spatial variation in WMPI. Accuracy in WMPI increased with increasing number of points sampled for all fire regimes and sampling designs, but the number of points needed to obtain accurate estimates was greater for fire regimes with complex spatial patterns of fire intervals than for those with relatively homogeneous patterns.

Effect of fire severity on long-term occupancy of burned boreal conifer forests by saproxylic insects and wood-foraging birds

2010 ◽  
Vol 19 (4) ◽  
pp. 500 ◽  
Author(s):  
Antoine Nappi ◽  
Pierre Drapeau ◽  
Michel Saint-Germain ◽  
Virginie A. Angers
Keyword(s):  
Boreal Forests ◽  
Fire Severity ◽  
Fire Regimes ◽  
Conifer Forests ◽  
Saproxylic Insects ◽  
Dead Trees ◽  
Brown Creeper ◽  
Canadian Boreal Forest ◽  
In Fire

Fire severity can vary greatly within and among burns, even in the Canadian boreal forest where fire regimes consist mostly of stand-replacing fires. We investigated the effects of fire severity on the long-term occupancy of burns by (i) saproxylic insects and (ii) three wood-foraging birds. Based on observations made 6 to 11 years after fire in burned conifer forests that varied in fire severity in Quebec, Canada, our results indicate that low-severity portions of the burns likely provided snag conditions suitable for the long-term presence of deadwood-associated insects and birds. The black-backed woodpecker, a post-fire forest specialist, was still abundant 6 and 8 years after fire. This pattern was likely explained by the persistence of several saproxylic insect species that are associated with recently dead trees and by the positive effect of lower fire severity on the abundance of Arhopalus foveicollis, a cerambycid with a long life cycle in dead wood. The American three-toed woodpecker and the brown creeper, and their associated prey (Scolytinae beetles), were more abundant in burned stands of lower v. higher severity. We conclude that less severely burned snags and stands within high-severity burns may favour the long-term presence of trophic webs that involve saproxylic insects and wood-foraging birds in burned boreal forests.

Interaction between peatland moisture and plant functional types drives fire dynamics in forested peatlands in central-western Siberia

2021 ◽  
Author(s):  
Angelica Feurdean ◽  
Andrei-Cosmin Diaconu ◽  
Geanina Butiseaca ◽  
Mariusz Galka ◽  
Simon M. Hutchinson ◽  
...  
Keyword(s):  
Boreal Forests ◽  
Western Siberia ◽  
Fire Regime ◽  
Fire Regimes ◽  
Forest Composition ◽  
Vegetation Composition ◽  
Picea Obovata ◽  
Peatland Hydrology ◽  
In Fire

<p>Boreal forests are among the ecosystems most significantly impacted by wildfires as a consequence of climate warming. A large proportion of the global boreal forest area is located in Siberia, however, its vast extent and restricted access limit datasets recording changes in wildfire activity, especially from a longer-term perspective. Such long-term records of wildfire activity are vital to understanding how fire regimes vary with changes in climate, vegetation composition and human-vegetation interaction, as well as the impacts of wildfires on boreal forests.</p><p>Here, we explore how patterns in fire regime (biomass burned, fire frequency, fire type) have changed over the Holocene. We focus on the relationship between fire regime, forest density and the fire-related traits of the main tree species, and peatland hydrology. We used charcoal-morphologies based reconstructions of fire regimes, along with pollen-based assessments of vegetation composition and testate amoebae-based hydro-climate reconstructions in Pinus-Betula dominated peatlands from central-western Siberia, Tomsk Oblast, Russia.</p><p>The occurrence of more severe fires (i.e., higher biomass burning per fire episode and abundant woody morphotypes) were recorded between 7500 and 5000 cal yr BP. Higher temperatures during that time, likely enhanced peatland dryness and fuel flammability creating conditions conducive to peat and forest fires. Drier peatland conditions also affected forest composition and density by favouring the expansion of a mix of light taiga and fire resisters (e.g., Pinus sylvestris, P. sibirica, Larix) with denser taiga and fire avoiders (Picea obovata and Abies sibirica) on the peatland. A shift to the lowest biomass burning and fire types affecting mostly litter and understorey vegetation, was registered between 4000 and 1500 cal yr BP. Temporally, it coincides with an increase in peatland surface moisture and a change in forest composition characterised by a decline in fire resisters, while fire avoiders remained abundant. An almost synchronous intensification in fires frequency and severity from ca. 2000 cal yr BP to the present at all sites, was concurrent with the rise to dominance of fire-invader species (Betula), as well as a more abundant biomass in the understory layer (shrubs, herbs, ferns, moss), while fire resisters and avoiders declined substantially. We found that Picea obovata to be highly vulnerable tree taxa to frequent, severe fires.</p><p>This long-term perspective demonstratesthat peatland hydrology is connected to, and feedbacks on peatland and forest composition and fuel dryness and ultimately fire regime. It also shows that more frequent fires of higher severity can lead to compositional or structural changes of forests, if trees cannot reach reproductive ages prior to the next burning events. Future predicted increases in temperatures are likely to enhance peatland drying, with cascading effects on forest and peat plant composition, subsequently exacerbating wildfire activity. This study thus contributes to an understanding of disturbance regimes in boreal forests and considers their potential to adapt to new climate conditions and fire regimes.</p><p> </p>

scholarly journals Effects of fire frequency on savanna butterfly diversity and composition: A preliminary study

Koedoe ◽  
2020 ◽  
Vol 62 (1) ◽  
Author(s):  
Elie Gaget ◽  
Catherine L. Parr ◽  
Clélia Sirami
Keyword(s):  
Species Richness ◽  
Low Frequency ◽  
Fire Regimes ◽  
Spatial Diversity ◽  
Fire Frequency ◽  
Management Tool ◽  
Butterfly Diversity ◽  
Fire Experiment ◽  
In Fire

Fire plays a major role in many biomes, is widely used as a management tool and is likely to be affected by climate change. For effective conservation management, it is essential to understand how fire regimes affect different taxa, yet responses of invertebrates are particularly poorly documented. We tested how different fire frequencies influence savanna butterfly diversity and composition by using a long-term savanna fire experiment initiated in 1954 in the Kruger National Park (South Africa). We compared butterfly abundance, species richness and community composition across three fire frequencies: high (burnt annually), medium (burnt triennially) and low (burnt twice in 60 years). Plots with high fire frequency hosted higher abundance than medium- or low-frequency plots. Fire frequencies did not affect species richness, but they led to distinct communities of butterflies. Our findings suggest that, in view of the three fire frequencies tested, a spatial diversity of fire frequencies may increase butterfly diversity at the landscape level in wet savannas. Managers may need to promote a greater diversity of fire frequencies by increasing fire frequency in some areas to provide habitat for species requiring high fire frequency, and by decreasing fire frequency in a large proportion of the landscape to provide fire refuges. This study provides new insights for butterfly conservation in savannas and highlights several knowledge gaps, which further studies should address for insect responses to be given adequate consideration in fire management strategies.Conservation implications: A spatial diversity of fire frequencies may increase butterfly diversity. Managers may need to promote a greater diversity of fire frequencies by increasing fire frequency in some areas to provide habitat for species requiring high fire frequency, and by decreasing fire frequency in other areas to provide fire refuges.

Quantifying the Pyrocene: How Important is Fire to Life on Earth?

2020 ◽  
Author(s):  
Claire Belcher
Keyword(s):  
Fire Regimes ◽  
Fire Frequency ◽  
Atmospheric Composition ◽  
Earth System ◽  
Atmospheric Conditions ◽  
Critical History ◽  
The Earth ◽  
Life On Earth ◽  
In Fire

<p>Fire and vegetation have a dual interaction with each other, whilst also both influencing the environment and atmosphere. For example, fire regimes are themselves controlled by atmospheric conditions, atmospheric composition, climate and the type of vegetation. Whilst, the effects of fires, the products and emissions they generate influence biogeochemical cycles and long-term Earth system processes through their impacts on nutrient cycles and by altering the composition and distribution of biomes. Hence fire is more than a simple agent of disturbance and has a multitude of complex feedbacks.</p><p>Wildfires have shaped our ecosystems and Earth system processes for some 420 million years. For example the presence of and changes in fire frequency and behaviour on evolutionary timescales has influenced the physiological traits of plants such that many ecologists have interpreted them as adaptations to fire. For example, serotiny in the Pine lineage is believed to have evolved millions of years ago in the Late Cretaceous period, where wildfires were both frequent and intense. Such traits seemingly continue to allow some plants to succeed in fire prone areas. However, humans have entirely altered ignition patterns, with some 95% of fires being started by man; we have altered the connectivity of fuels in landscapes, species composition and fuel structure. Yet we have limited understanding to what extent we have disrupted fire feedbacks to the Earth system. This lies in large part because we have not yet well understood what natural feedbacks fire has had on our planet throughout its history.</p><p>In this talk I will explore some of the critical history of fire and some of the processes that fire appears to regulate in order to pose the question - are fires a critical resource that secures the long-term balance of the Earth system that keeps our planet habitable to man?</p>

scholarly journals Decadal changes in fire frequencies shift tree communities and functional traits

2020 ◽  
Author(s):  
Adam F. A. Pellegrini ◽  
Tyler Refsland ◽  
Colin Averill ◽  
César Terrer ◽  
A. Carla Staver ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Fire History ◽  
Vegetation Type ◽  
Basal Area ◽  
Fire Regimes ◽  
Fire Frequency ◽  
Tree Communities ◽  
In Fire ◽  
The Impact

Global change has resulted in chronic shifts in fire regimes, increasing fire frequency in some regions and decreasing it in others. Predicting the response of ecosystems to changing fire frequencies is challenging because of the multi-decadal timescales over which fire effects emerge and the variability in environmental conditions, fire types, and plant composition across biomes. Here, we address these challenges using surveys of tree communities across 29 sites that experienced multi-decadal alterations in fire frequencies spanning ecosystems and environmental conditions. Relative to unburned plots, more frequently burned plots had lower tree basal area and stem densities that compounded over multiple decades: average fire frequencies reduced basal area by only 4% after 16 years but 57% after 64 years, relative to unburned plots. Fire frequency had the largest effects on basal area in savanna ecosystems and in sites with strong wet seasons. Analyses of tree functional-trait data across North American sites revealed that frequently burned plots had tree communities dominated by species with low biomass nitrogen and phosphorus content and with more efficient nitrogen acquisition through ectomycorrhizal symbioses (rising from 85% to nearly 100%). Our data elucidate the impact of long-term fire regimes on tree community structure and composition, with the magnitude of change depending on climate, vegetation type, and fire history. The effects of widespread changes in fire regimes underway today will manifest in decades to come and have long-term consequences for carbon storage and nutrient cycling.

Fire regime shift linked to increased forest density in a piñon–juniper savanna landscape

2014 ◽  
Vol 23 (2) ◽  
pp. 234 ◽  
Author(s):  
Ellis Q. Margolis
Keyword(s):  
Regime Shift ◽  
Fire History ◽  
Fire Regime ◽  
Fire Regimes ◽  
Fire Frequency ◽  
Climatic Conditions ◽  
Tree Density ◽  
High Severity ◽  
Wide Range ◽  
In Fire

Piñon–juniper (PJ) fire regimes are generally characterised as infrequent high-severity. However, PJ ecosystems vary across a large geographic and bio-climatic range and little is known about one of the principal PJ functional types, PJ savannas. It is logical that (1) grass in PJ savannas could support frequent, low-severity fire and (2) exclusion of frequent fire could explain increased tree density in PJ savannas. To assess these hypotheses I used dendroecological methods to reconstruct fire history and forest structure in a PJ-dominated savanna. Evidence of high-severity fire was not observed. From 112 fire-scarred trees I reconstructed 87 fire years (1547–1899). Mean fire interval was 7.8 years for fires recorded at ≥2 sites. Tree establishment was negatively correlated with fire frequency (r=–0.74) and peak PJ establishment was synchronous with dry (unfavourable) conditions and a regime shift (decline) in fire frequency in the late 1800s. The collapse of the grass-fuelled, frequent, surface fire regime in this PJ savanna was likely the primary driver of current high tree density (mean=881treesha–1) that is >600% of the historical estimate. Variability in bio-climatic conditions likely drive variability in fire regimes across the wide range of PJ ecosystems.

scholarly journals Evaluating the Performance of a Forest Succession Model to Predict the Long-Term Dynamics of Tree Species in Mixed Boreal Forests Using Historical Data in Northern Ontario, Canada

Forests ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1181
Author(s):  
Guy R. Larocque ◽  
F. Wayne Bell
Keyword(s):  
Populus Tremuloides ◽  
Boreal Forests ◽  
Forest Ecosystems ◽  
Forest Succession ◽  
Regional Scale ◽  
Abies Balsamea ◽  
Forest Growth ◽  
Northern Ontario ◽  
Phase Dynamics

Environmental concerns and economic pressures on forest ecosystems have led to the development of sustainable forest management practices. As a consequence, forest managers must evaluate the long-term effects of their management decisions on potential forest successional pathways. As changes in forest ecosystems occur very slowly, simulation models are logical and efficient tools to predict the patterns of forest growth and succession. However, as models are an imperfect representation of reality, it is desirable to evaluate them with historical long-term forest data. Using remeasured tree and stand data from three data sets from two ecoregions in northern Ontario, the succession gap model ZELIG-CFS was evaluated for mixed boreal forests composed of black spruce (Picea mariana [Mill.] B.S.P.), balsam fir (Abies balsamea [L.] Mill.), jack pine (Pinus banksiana L.), white spruce (Picea glauca [Moench] Voss), trembling aspen (Populus tremuloides Michx.), white birch (Betula papyrifera Marsh.), northern white cedar (Thuja occidentalis L.), American larch (Larix laricina [Du Roi] K. Koch), and balsam poplar (Populus balsamefera L.). The comparison of observed and predicted basal areas and stand densities indicated that ZELIG-CFS predicted the dynamics of most species consistently for periods varying between 5 and 57 simulation years. The patterns of forest succession observed in this study support gap phase dynamics at the plot scale and shade-tolerance complementarity hypotheses at the regional scale.

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