Interactions between dense Callitris regeneration and Eucalyptus and Callitris canopy trees in semiarid woodlands

2012 ◽  
Vol 60 (6) ◽  
pp. 549 ◽  
Author(s):  
Janet S. Cohn ◽  
Ian D. Lunt ◽  
Ross A. Bradstock ◽  
Terry Koen
Keyword(s):  
Fire Frequency ◽  
Eucalyptus Species ◽  
Rainfall Gradient ◽  
European Settlement ◽  
Canopy Trees ◽  
Tree Canopies ◽  
Callitris Glaucophylla ◽  
Compositional Changes ◽  
In Fire

Since European settlement, woodlands have undergone significant structural and compositional changes in semiarid SE Australia. With logging, introduced grazing and declines in fire frequency, fire-sensitive Callitris glaucophylla has regenerated densely in woodlands dominated by C. glaucophylla and fire-tolerant Eucalyptus species. Since little is known about long-term competitive interactions between sapling regeneration and canopy trees, we examined: (1) how established Eucalyptus and Callitris canopy trees influence survival, growth and reproduction of Callitris saplings; (2) whether dense Callitris regeneration affects canopy tree health during drought; and (3) whether these patterns differ along a rainfall gradient (363–621 mm year–1). Callitris saplings beneath tree canopies were less dense, smaller, and less likely to fruit than isolated saplings in gaps along the rainfall gradient. Callitris trees surrounded by Callitris regeneration had greater mortality than those without surrounding regeneration; Eucalyptus trees were more likely to be drought stressed at the lower end of the rainfall gradient, where canopy trees were at higher densities. The results suggest that canopy trees reduce the density rather than exclude Callitris regeneration, and that the regeneration contributes to mortality of Callitris canopy trees during drought. The trend towards increasing Callitris dominance is expected to continue over time, owing to the paucity of Eucalyptus recruitment.

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 Postglacial Fire Frequency and its Relation to Long-Term Vegetational and Climatic Changes in Yellowstone Park

1992 ◽  
Vol 16 ◽  
pp. 212-218
Author(s):  
Cathy Whitlock
Keyword(s):  
Fire Regime ◽  
Fire Frequency ◽  
Northern Rocky Mountains ◽  
Modern Pollen ◽  
Pollen Rain ◽  
History Of ◽  
Fossil Records ◽  
In Fire ◽  
The Relationship

The primary research objective has been to study the vegetational history of Yellowstone and its sensitivity to changes in climate and fire frequency. To establish a sequence of vegetational changes, a network of pollen records spanning the last 14,000 years has been studied from different types of vegetation within the Park. The relationship between modern pollen rain, modern vegetation and present­day climate in the northern Rocky Mountains has been the basis for interpreting past vegetation and climate from the fossil records. Changes in fire regime during the past 14,000 years have been inferred from sedimentary charcoal and other fire proxy in lake sediments. Calibration of the fire signal is based on a study that measures the input of charcoal into lakes following the 1988 fires in Yellowstone.

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.

Landscape ecology of the burrowing bettong: fire and marsupial biocontrol of shrubs in semi-arid Australia

2007 ◽  
Vol 29 (1) ◽  
pp. 107 ◽  
Author(s):  
James C. Noble ◽  
David S. Hik ◽  
Anthony R. E. Sinclair
Keyword(s):  
Habitat Preferences ◽  
Fire Frequency ◽  
European Settlement ◽  
South Wales ◽  
Arid Rangelands ◽  
Native Shrubs ◽  
In Fire ◽  
The 19Th Century ◽  
Semi Arid ◽  
Stony Hard

Prior to European settlement, medium-sized marsupials, especially bettongs (Bettongia spp.), were widely distributed across arid and semi-arid Australia. Most disappeared rapidly in the late 1800s in the earliest settled rangelands such as the West Darling region of western New South Wales following the spread of domestic herbivores, rabbit invasion, exotic predators and loss of habitat. Because the burrowing bettong (Bettongia lesueur) is the only fossorial macropod species, it left a clearly visible record of its past presence, distribution and habitat preferences in the form of substantial relict warrens, particularly in stony, ‘hard-red’ habitats. With the reduction in fire frequency because of excessive grazing pressures following European settlement in the 19th century, there was a rapid increase in the density of unpalatable native shrubs. We examine the hypothesis that periodic wildfires and browsing by bettongs were together able to regulate shrub densities in semi-arid rangelands in Australia. Information from various sources concerning the effects of fire, rainfall and browsing on the demography of shrubs was used to construct a model of shrub population dynamics. The model indicates the potential for two states for a given bettong density: first, a low shrub density maintained by a combination of periodic fire and bettong browsing; and second, a high shrub density in the absence of fire. These results have broad implications for pastoral and conservation management in Australian semi-arid rangelands.

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.

Recovery of treeless subalpine vegetation in Kosciuszko National Park after the landscape-scale fire of 2003

2015 ◽  
Vol 63 (7) ◽  
pp. 597 ◽  
Author(s):  
K. L. McDougall ◽  
N. G. Walsh ◽  
G. T. Wright
Keyword(s):  
Plant Communities ◽  
National Park ◽  
Fire Frequency ◽  
Landscape Scale ◽  
Vegetation Types ◽  
Sensitive Species ◽  
Compositional Changes ◽  
Regeneration Strategies ◽  
Fire Intervals ◽  
In Fire

The vegetation of fire-prone landscapes is influenced by the frequency, severity, seasonality, return interval and stochastic patterning of fire as well as the responses of its component species. An expected increase in fire frequency and severity in association with global warming may result in compositional changes within, and spatial reorganisation of, plant communities; indeed, some plant communities may even face extinction. Vegetation dominated by fire-sensitive species may be most vulnerable to change in fire frequency. A landscape-scale fire in Kosciuszko National Park in 2003 provided an opportunity to compare recovery in vegetation dominated by resprouters and fire-sensitive, obligate seeders. We hypothesised that if plant assemblages had failed to recover after 10 years in terms of species richness and cover they would have been dominated by seeder species pre-fire. After 10 years, two of the six vegetation types investigated had recovered and these were indeed dominated by resprouter species. Two groundwater-dependent vegetation types (one resprouter-dominated and one dominated by fire-sensitive species) were close to recovery. However, the other two types, non-groundwater-dependent shrublands dominated by both seeder and resprouter species, were still far from recovery at that time, with shrub cover reduced and grass cover increased. The likelihood of recovery after 10 years therefore does not appear to be solely a consequence of the regeneration strategies of the dominant species. Post-fire environmental factors (e.g. grazing, disease, climate) may be just as important as regeneration strategies in determining recovery time. Because not all vegetation had recovered after 10 years, prediction of minimum tolerable fire intervals at a landscape scale is impossible at this time. Future fire management needs to be adaptive, taking into account post-fire influences, rather than prescriptive.

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.

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