Anthropogenic Fires Research Articles

Exploring potential drivers of European biomass burning over the Holocene: a data‐model analysis

AbstractAimTo reconstruct spatial and temporal patterns of European fire activity during the Holocene and to explore their potential drivers, by relating biomass burning to simulated biotic and abiotic parameters.LocationEurope.MethodsHolocene fire activity was investigated based on 156 sedimentary charcoal records from lakes and peat bogs across Europe. Charcoal data covering the last 9000 years were statistically compared with palaeoclimate data derived from the Max Planck Institute for Meteorology/University of Wisconsin‐Madison Earth System Model, with vegetation and fire indices simulated with the dynamic vegetation model lpj‐guess and with two independent scenarios of past anthropogenic land‐cover change.ResultsThe combined sedimentary charcoal records suggest that there was little fire activity during the early and the middle Holocene compared with recent millennia. A progressive increase in fire frequency began around 3500 cal. yr bp and continues into the late Holocene. Biomass burning rose sharply from 250 cal. yr bp onwards, reaching a maximum during the early Industrial Era and then declining abruptly. When considering the whole Holocene, the long‐term control of fire is best explained by anthropogenic land‐cover change, litter availability and temperature‐related parameters.Main conclusionsWhile the general patterns found across Europe suggest the primary role of vegetation, precipitation and temperature‐related parameters in explaining fire dynamics during the early Holocene, the increase in fire activity observed in the mid–late Holocene is mainly related to anthropogenic land‐cover changes, followed by vegetation and temperature‐related parameters. The 20th‐century decline in biomass burning seems to be due to increased landscape fragmentation and active fire suppression policies. Our hypothesis that human activities played a primary role in Holocene biomass burning across Europe could be tested by improved palaeoclimate reconstructions and more refined representations of anthropogenic fires in climate and vegetation models.

Invasive ants as back-seat drivers of native ant diversity decline in New Caledonia

Biological invasions are typically associated with disturbance, which often makes their impact on biodiversity unclear—biodiversity decline might be driven by disturbance, with the invader just being a ‘passenger’. Alternatively, an invader may act as a ‘back-seat driver’, being facilitated by disturbance that has already caused some biodiversity decline, but then causing further decline. Here we examine the interactive effects of anthropogenic fire and invasive ant species (Anoplolepis gracilipes or Wasmannia auropunctata) on native ant diversity in New Caledonia, a globally recognized biodiversity hotspot. We first examined native ant diversity at nine paired burnt and unburnt sites, with four pairs invaded by Anoplolepis, 5 years after an extensive fire. In the absence of invasion, native epigaeic ants were resilient to fire, but native ant richness and the abundance of Forest Opportunists were markedly lower in invaded burnt sites. Second, we examined native ant diversity along successional gradients from human-derived savanna to natural rainforest in the long-term absence of fire, where there was a disconnection between disturbance-mediated variation in microhabitat and the abundance of the disturbance specialist Wasmannia. All native ant diversity responses (total abundance, richness, species composition, functional group richness and the abundance of Forest Opportunists) declined independently of microhabitat variables but in direct association with high Wasmannia abundance. Our results indicate that invasive ants are acting as back-seat drivers of biodiversity decline in New Caledonia, with invasion facilitated by disturbance but then causing further biodiversity decline.

Environmental drivers and spatial dependency in wildfire ignition patterns of northwestern Patagonia

Fire management requires an understanding of the spatial characteristics of fire ignition patterns and how anthropogenic and natural factors influence ignition patterns across space. In this study we take advantage of a recent fire ignition database (855 points) to conduct a comprehensive analysis of the spatial pattern of fire ignitions in the western area of Neuquén province (57,649 km2), Argentina, for the 1992–2008 period. The objectives of our study were to better understand the spatial pattern and the environmental drivers of the fire ignitions, with the ultimate aim of supporting fire management. We conducted our analyses on three different levels: statistical “habitat” modelling of fire ignition (natural, anthropogenic, and all causes) based on an information theoretic approach to test several competing hypotheses on environmental drivers (i.e. topographic, climatic, anthropogenic, land cover, and their combinations); spatial point pattern analysis to quantify additional spatial autocorrelation in the ignition patterns; and quantification of potential spatial associations between fires of different causes relative to towns using a novel implementation of the independence null model. Anthropogenic fire ignitions were best predicted by the most complex habitat model including all groups of variables, whereas natural ignitions were best predicted by topographic, climatic and land-cover variables. The spatial pattern of all ignitions showed considerable clustering at intermediate distances (<40 km) not captured by the probability of fire ignitions predicted by the habitat model. There was a strong (linear) and highly significant increase in the density of fire ignitions with decreasing distance to towns (<5 km), but fire ignitions of natural and anthropogenic causes were statistically independent. A two-dimensional habitat model that quantifies differences between ignition probabilities of natural and anthropogenic causes allows fire managers to delineate target areas for consideration of major preventive treatments, strategic placement of fuel treatments, and forecasting of fire ignition. The techniques presented here can be widely applied to situations where a spatial point pattern is jointly influenced by extrinsic environmental factors and intrinsic point interactions.

Threats to and viability of the giant anteater, Myrmecophaga tridactyla (Pilosa: Myrmecophagidae), in a protected Cerrado remnant encroached by urban expansion in central Brazil

Urbanization poses a serious threat to wildlife populations inhabiting native vegetation remnants surrounded by the expanding urban and suburban sprawl. The close contact with human activities causes not only direct impacts, such as habitat loss, but also indirect negative effects, such as population isolation, roadkills and anthropogenic fires. The Parque Nacional de Brasilia is a large Cerrado remnant almost completely surrounded by the city of Brasilia, in central Brazil. Here, we use population viability analysis to model the impacts of urbanization on a population of Myrmecophaga tridactyla (Linnaeus, 1758) inhabiting that park. Our results show that roadkill mortality is by far the most serious threat to the long-term persistence of the giant anteater in the study site. The implementation of measures to better control vehicle speed in the vicinity of the park is urgently needed if we expect the giant anteater population to be effectively protected in the Parque Nacional de Brasilia.

Genetic diversity of Brachystegia boehmii Taub. and Burkea africana Hook. f. across a fire gradient in Niassa National Reserve, northern Mozambique

Miombo woodlands constitute the most important type of vegetation in southern Africa, covering about 70% of the Zambezian phytoregion. This ecosystem, dominated by the genera Brachystegia , Julbernardia and Isoberlinia , has an immeasurable socio-economic and environmental value, playing a key role in formal and informal economies and in energy, water and carbon balances. Anthropogenic fires represent one of the major threats, compromising the stability of miombo. In this study we report on the usefulness of ISSR markers to assess, for the first time, the genetic diversity in two typical miombo species, Brachystegia boehmii Taub. and Burkea africana Hook. f. across a fire gradient in the Niassa National Reserve (NNR). According to our data, ISSR seem to be a suitable molecular marker's system for biodiversity studies in both species, generating high levels of polymorphisms coupled with a convenient resolving power. The results point to a link between fire-tolerance and genetic diversity, as judged by the higher diversity levels observed in B. africana (fire-tolerant) and by the evolutive fire response of B. boehmii . Although fire differentially affects the biodiversity in each species, in general, the overall genetic diversity was high and their survival does not seem to be compromised by the frequency of fires, agreeing with the fact that NNR is one of the least disturbed areas of deciduous miombo. ► We report on the assessment of the genetic diversity in two miombo species. ► There is a correlation between fire-tolerance and genetic diversity. ► There is a good genetic potential for Burkea africana and Brachystegia boehmii. ► The current fire frequency is affecting differently miombo species.

Restoration release of overtopped Oregon white oak increases 10-year growth and acorn production

In the Willamette Valley–Puget Trough–Georgia Basin ecoregion of the North American Pacific Northwest, there has been widespread encroachment of Douglas-fir (Pseudotsuga menziesii) upon Oregon white oak (Quercus garryana) savanna and woodland stands that were historically maintained by frequent anthropogenic fire. Restoration of these stands requires removal of the Douglas-fir overstory, although there is little information on how oak trees that have been suppressed for decades respond to release. Our objective was to evaluate the 10-year response of oak trees to three release treatments from overtopping Douglas-fir in a study replicated at four western Washington sites. Treatments were: full release (removal of all Douglas-fir within a radius equal to the oak’s height), half release (removal of Douglas-fir within a half-height radius), and thin only (stand-level commercial thinning of the Douglas-fir overstory; oaks not targeted for release). Periodic diameter growth of oak trees in the full-release treatment was significantly greater (by as much as 243%) than that in the other treatments and increased with time since treatment. Oak height and crown area growth rates were not influenced by treatment, but larger pre-treatment crown size was associated with greater post-treatment diameter growth and acorn production. Full release increased acorn production compared to thin only in years when region-wide production was moderate to high (5 of 9years); half release increased production relative to thin only in 2 of 9years, but to a lesser degree. Height growth of residual Douglas-fir trees was greater than that of oak trees in all treatments. The increasing post-treatment growth rate of the fully released oak trees and their increased acorn production indicate the capacity of long-suppressed Oregon white oak to rapidly recover following complete removal of a conifer overstory. The oak trees showed no negative effects following the dramatic change in environment associated with this treatment. Thus, a single-entry, complete release from overtopping conifers was effective in restoring overstory structure and composition, which is an initial step in restoration of invaded oak woodland or savanna.

Natural and cultural histories of fire differ between Tasmanian and mainland Australian alpine vegetation

We ask how and why mainland Australia and Tasmania differ in the natural and cultural history of alpine fire. Indigenous people seem unlikely to have extensively burned the alpine landscape in either of mainland Australia or Tasmania, whereas anthropogenic fire increased markedly after the European invasion. In Tasmania, where lightning ignition is uncommon, alpine fires have been rare post-1980, whereas mainland alpine vegetation has been extensively burned. The current distributions of the eight Australian alpine plant species that have no mechanisms for recovery from fire suggest that climate and natural fire barriers have been important in their survival. Mainland Australian pre-fire vegetation cover is typically attained in less than a decade, whereas in Tasmania, half a century or more after fire, bare ground persists at high levels, and continues to decrease only where mammalian herbivores are excluded. These differences appear to be ultimately related to the climatic contrast between the maritime mountains of Tasmania and the continental mainland mountains, through the effects of continentality on snow cover, which, in turn affect marsupial herbivore grazing, exposure of soil and vegetation to extreme microclimatic conditions and the degree of shrub dominance.

Alterations in Molecular Composition of Humic Substances from Eucalypt Plantation Soils Assessed by 13C‐NMR Spectroscopy

Land‐use changes with natural vegetation removal may impact the quantity and quality of humic substances (HS), including their molecular nature. Nuclear magnetic resonance (NMR) experiments were used in the present study to evaluate the alterations in the molecular composition of fulvic (FA) and humic (HA) acids from soils under eucalypt plantations in three major biomes in Brazil: Atlantic Forest, Cerrado, and Grassland. The major NMR‐identifiable components in these HS were aromatics including aromatic C‐O, COO/NC = O groups, peptides, carbohydrates, lignin‐derived moieties and nonpolar alkyls. In all biomes the dipolar dephasing technique indicated the presence of significant amounts of condensed aromatic C, possibly inherited from charred materials derived from natural and anthropogenic fires in the region. The nonpolar alkyl C to O‐alkyl C ratio averaged 1.4 for HA and 1.1 for FA. Humic substances from eucalypt soils showed greater contribution of nonpolar alkyl groups and a smaller abundance of O‐alkyl groups in comparison to the native vegetation soil. Sugarcane (Saccharum officinarum L.) cultivation increased HA aromatics in comparison to those from the native Atlantic Forest soil, but when sugarcane was substituted by eucalypt the aromatics decreased and O‐alkyl C recovered in HA and FA. There was evidence of greater contribution of lignin‐derived C for HA and FA in sites planted with Brachiaria spp. pastures. Except for the HA from one Cerrado soil (Itacambira), aromaticity of HA decreased following planting to eucalypt. These changes in HS molecular composition across biomes may have impact on soil organic matter processes and they should be taken into account in future studies.

Fuel Conditions Associated with Native and Exotic Grasses in a Subtropical Dry Forest in Puerto Rico

AbstractExotic grasses capable of increasing frequency and intensity of anthropogenic fire have invaded subtropical and tropical dry forests worldwide. Since many dry forest trees are susceptible to fire, this can result in decline of native species and loss of forest cover. While the contribution of exotic grasses to altered fire regimes has been well documented, the role of native grasses in contributing to fuel loads in dry forest has received little attention. We assessed differences in fuel conditions among native and exotic grasses within a subtropical dry forest preserve in Puerto Rico. We quantified fine fuel loads, fuel continuity, and seasonal changes in percent dead grass among the following grass patch types: (1) native grass with no known history of recent fire, (2) exotic grass that had burned once (single burn), and (3) exotic grass that burns frequently. Sampling was conducted during one wet season (August to October 2008) and again in the following dry season (February to March 2009). Overall, fine fuel loading was highest in native grass, but this was due to woody fuels rather than grass fuels. Percent of dead grass fuels increased with the transition from wet to dry season, and this increase was more pronounced for exotic grasses. Fuel continuity was highest in frequently burned exotic grass. Differences in grass phenology and fuel continuity may contribute to differences in fire frequency among native and exotic grass patches. Fuel management focused on prescribed fire should be used in conjunction with restoration of tree canopy to reduce fuels and limit development of a grass-fire cycle.

Customary Fire Regimes and Vegetation Structure in Gabon’s Bateke Plateaux

Most fires in Africa are anthropogenic yet remain understudied. Studies typically address managed fire, or the “fire triad” of early dry season-late dry season-suppression, and fire regimes which are annual or less, leaving unstudied the anthropogenic fire regimes that occur in the majority of African savannas. I take the case of the Bateke Plateaux area where burning today occurs both annually and semi-annually and measure the impacts of these regimes on savanna structure, measuring stem survival post fire and post fire regeneration of resprouts of the dominant savanna tree. While annual fires are hot and burn completely, semi-annual fires are cooler and patchy, favouring re-sprout survival and an escape route for small stems to mature into trees. This work extends the fire triad model to include an anthropogenic semi-annual regime which favours tree survival. The integration of local fire regimes into future studies will help increase our understanding of climate, vegetation dynamics as well as help orient policy and conservation.

Prehistoric land use at an archaeological hot-spot (the rock art park of Campo Lameiro, NW Spain) inferred from charcoal, synanthropic pollen and non-pollen palynomorph proxies

Pollen, non-pollen palynomorphs and charcoal from a colluvial soil surrounded by prehistoric petroglyphs (Campo Lameiro, NW Spain) were studied in order to assess the nature of human activities and their impact on Holocene vegetation patterns. Several phases of anthropogenic impact were observed. (i) Between 7.6 and 6.5 ka cal BP, synanthropic taxa (Urtica dioica type, Plantago lanceolata type) and coprophilous fungi (e.g. Sporormiella-type) are indicative of early (pre-agricultural) creation of small patches of pasture using fire, possibly for incipient animal husbandry or as part of a deliberate strategy to improve game availability. Such activities only had a minor effect on the deciduous Quercus-dominated forest established earlier during the Holocene Thermal Maximum. (ii) Between 5.9 and 4.8 ka cal BP a more intense signal indicative of pastoral activity was detected, corresponding to the Neolithic period. (iii) Between 4.8 and 3.4 ka cal BP, which fits within the hypothetical timeframe of petroglyph creation, the synanthropic and humidity (e.g. Cyperaceae, Mougeotia) indicators diminished while charcoal concentration increased, which can be explained by Mid-Holocene cooling/drying (Neoglaciation) in combination with reduced human impact, or by non-pastoral activities in the area possibly in association with the development of the rock art culture, converting pasture to protected open ground through anthropogenic fires. (iv) During the Late Bronze Age and Early Iron Age (3.4–2.5 ka cal BP), grazing pressure and fire regime intensity are high, coinciding with evidence of regional forest regression, despite an amelioration in climate. (v) Later phases, not corresponding to prehistoric rock art contexts, include a phase of heavy grazing and reduced fire frequency (from ca. 2.5 to 1.2 ka cal BP) as well as the near complete elimination of the deciduous woodland, the expansion of ericaceous shrubland and the evidence of local agriculture and afforestation. These results are consistent with earlier studies in the area and highlight the spatial heterogeneity in the vegetation especially during periods of prehistoric anthropogenic interference.

The reproductive response of an endemic bunchgrass indicates historical timing of a keystone process

Restoration of the Pinus palustris (longleaf pine)‐wiregrass ecosystem of the southeastern United States requires information on reference conditions such as the historical fire regime. Aristida beyrichiana (wiregrass), a keystone perennial bunchgrass, was historically widespread throughout the southeast, but its dependence upon growing season fires for sexual reproduction hastened its decline in the face of decades of human fire suppression. The reproductive response of wiregrass is described by patterns of meristem allocation between competing life history strategies (i.e., vegetative growth vs. sexual reproduction). The temporal link between fire and flowering indicates this allocation was optimized to the historical fire regime through selection. In this study, we used the observed allocation of wiregrass reproductive effort to sexual reproduction as the response variable to examine reproductive response to fire season, using plant size as a covariate. Sexual reproduction was positively associated with plant size. Plants burned during early summer (May–June) produced a greater proportion of inflorescences than did those burned in early spring (March–April) or in late summer (August). Using state records of natural (lightning‐ignited) and anthropogenic (human‐ignited) fires from historical (1933–1946) and contemporary (1998–2010) periods we found that the distribution of maximum wiregrass reproductive output most closely reflected the distribution of historical fires with natural ignition sources. Moreover, while the monthly distributions of historical and contemporary fires were different for anthropogenic ignitions, they did not differ for fires with natural ignitions. Our predictions of peak allocation based upon the biology of wiregrass provide strong support for the use of wiregrass as an indicator of the historical fire season (early summer). Efforts to restore the longleaf pine ecosystem should therefore consider the biological response of wiregrass in planning prescribed fires.

Resilience of an ancient tropical forest landscape to 7500 years of environmental change

There is growing recognition that the fate of the world’s terrestrial biodiversity depends on the management of human-dominated tropical forest landscapes. While global environmental change is transforming the ecology of tropical forests, a number of studies have also demonstrated that tropical forests are able to recover following disturbance. But are tropical forests resilient to environmental and anthropogenic disturbances over timescales of centuries or millennia? Here we examine the relationship between vegetation cover and variation in monsoon rainfall, soil erosion, and fire over 7500years in an ancient tropical landscape in the Western Ghats of India. We collected two overlapping sediment sequences at one study site and analysed them with palaeoecological techniques to reconstruct vegetation cover. Results suggest that climate and land-use changes might have had synergistic effects on this forested landscape, although the relationship between these factors and vegetation cover has varied over time. Results also indicate that the weakening of monsoon around 5750 BP might have caused a threshold event altering this landscape to a low tree-cover state. Although anthropogenic fire has maintained this landscape in low tree cover state from 3500 BP, this degraded tree–grassland mosaic has remained relatively resilient to fluctuations in environmental and anthropogenic factors. Tree taxa present throughout the sequence have lighter seeds than those absent in parts of the sequence, suggesting that dispersal mode might be an important factor in their persistence. Despite maintaining a degraded and fragmented forest mosaic, however, this landscape has supported populations of heavy-seeded trees and a probable refuge to their dispersal agents. We suggest that retaining tree cover on this landscape, even if fragmented, is key to maintaining its ecological resilience to environmental and anthropogenic disturbance.

Fire promotes growth and reproduction of Saccharum spontaneum (L.) in Panama

Fire can be an important mechanism by which invasive grasses maintain their dominance in introduced habitats. In April 2009 a dense stand of Saccharum spontaneum in the Panama Canal Watershed burned as a result of an anthropogenic fire. Regrowth was monitored throughout the 2009 growing season and compared to a nearby unburned stand with a similar management history. Six months after the fire, live aboveground biomass and stem density were similar but flowering shoot densities were significantly higher in the burned stand. Aboveground dead biomass was significantly higher in the unburned stand, and bare soil remained below much of the burned stand. Viability of seeds produced in the burned stand was comparable to surrounding unburned populations. Germinants were also observed in the burned stand in October and November whereas no seedlings were found in the unburned stand. These results suggest that fire promotes the growth of Saccharum and may enhance its spread by stimulating new shoot growth, increasing flowering shoot density and thereby seed production, and creating available habitat for recruitment of new populations by removing litter. It also may delay flowering thus extending the reproductive period of the species in Panama. Appropriate measures, including increased funding for fire control and public education, to reduce the frequency of dry-season fires would likely help to manage the spread of this very aggressive invader in Panama.

Spatial complexity in fragmenting Amazonian rainforests: Do feedbacks from edge effects push forests towards an ecological threshold?

Deforestation and resulting landscape fragmentation are important concerns in many tropical areas. Deforestation is a complex process with many potential feedback loops, many of which are ignored in models that attempt to interpolate forest loss based on past deforestation rates. In addition, most ecological studies of the impacts of deforestation have focused on landscapes that are already fragmented. These studies ignore the fact that edge effects, such as anthropogenic fire, reach their maximum well before habitat connectivity is lost and may create positive feedbacks that result in further fragmentation. We developed a simple model to explore the potential influence of edge effects on fragmentation rates and used remotely sensed data from the MAP (Madre de Dios, Acre, and Pando) region of the Brazilian Amazon to parameterize the relationships of interest. Under reasonable real-world parameter combinations, edge effects can have a significant impact on deforestation rates, supporting the hypothesis that the true tipping point in a forest to pasture regime shift occurs earlier (i.e., ∼50% forest loss) than analysis of a loss in connectivity would suggest (i.e., ∼60% forest loss). Our results have important implications for understanding deforestation, edge-driven processes, regime shifts, and the management of complex pattern-process relationships.

The Aftermath of Megafaunal Extinction: Ecosystem Transformation in Pleistocene Australia

Giant vertebrates dominated many Pleistocene ecosystems. Many were herbivores, and their sudden extinction in prehistory could have had large ecological impacts. We used a high-resolution 130,000-year environmental record to help resolve the cause and reconstruct the ecological consequences of extinction of Australia's megafauna. Our results suggest that human arrival rather than climate caused megafaunal extinction, which then triggered replacement of mixed rainforest by sclerophyll vegetation through a combination of direct effects on vegetation of relaxed herbivore pressure and increased fire in the landscape. This ecosystem shift was as large as any effect of climate change over the last glacial cycle, and indicates the magnitude of changes that may have followed megafaunal extinction elsewhere in the world.

Rapid climate change and no-analog vegetation in lowland Central America during the last 86,000 years

Glacial–interglacial climate cycles are known to have triggered migrations and reassortments of tropical biota. Although long-term precessionally-driven changes in temperature and precipitation have been demonstrated using tropical sediment records, responses to abrupt climate changes, e.g. the cooling of Heinrich stadials or warmings of the deglaciation, are poorly documented. The best predictions of future forest responses to ongoing warming will rely on evaluating the influences of both abrupt and long-term climate changes on past ecosystems. A sedimentary sequence recovered from Lake Petén-Itzá, Guatemalan lowlands, provided a natural archive of environmental history. Pollen and charcoal analyses were used to reconstruct the vegetation and climate history of the area during the last 86,000 years. We found that vegetation composition and air temperature were strongly influenced by millennial-scale changes in the North Atlantic Ocean. Whereas Greenland warm interstadials were associated with warm and relatively wet conditions in the Central American lowlands, cold Greenland stadials, especially those associated with Heinrich events, caused extremely dry and cold conditions. Even though the vegetation seemed to have been highly resilient, plant associations without modern analogs emerged mostly following sharp climate pulses of either warmth or cold, and were paralleled by exceptionally high rates of ecological change. Although pulses of temperature change are evident in this 86,000-year record none matched the rates projected for the 21st Century. According to our findings, the ongoing rapid warming will cause no-modern-analog communities, which given the improbability of returning to lower-than-modern CO2 levels, anthropogenic barriers to migration, and increased anthropogenic fires, will pose immense threats to the biodiversity of the region.

The effect of forest fires in emissions of biogenic volatile organic compounds and windblown dust over urban areas

This study examines the impact of forest fires on natural biogenic volatile organic compounds (BVOCs) and windblown dust emissions over urban areas; specifically over the Athens larger urban zone for the reference year 2008. The area spans a continuum of urban–suburban–wild lands and suffers air quality problems with respect to particulate matter (PM) which are frequently exacerbated during the summer due also to forest fire events. Although the anthropogenic, natural and forest fire emissions in the area have been well documented in the past, the indirect effect of forest fires on natural emissions has not been estimated. A brief description of the area and the history of forest fires events during the period 2000–2008 are presented together with an emission inventory for particulate matter (PM2.5 and PM2.5–10) and non-methane VOC (NMVOC), precursor to PM, from anthropogenic and natural sources for the reference year 2008. The effect of large forest fires (over 40 ha) during the period 2000–2008 on natural emissions is examined with respect also to the spatial and temporal distribution and their relative contribution to total emissions over the area. Moreover, the effect of several parameters and assumptions used in natural emissions calculations pre and post-fire events is discussed. The results indicate that there is a trade-off between fire effects that can result in an increase in PM10 windblown dust emissions but decrease of BVOCs emissions due to vegetation reduction. The changes in natural BVOCs and PM10 emissions over the selected area are rather small, specifically 3.5% and 1.7%, respectively. Changes in the relative contribution of natural to total PM10 and NMVOC emissions in the area due to forest fires was also found small, approximately 0.5% and 0.7%, respectively. The contribution of anthropogenic emissions appears to dramatically outweigh the potential effects on air quality from natural emissions and their changes due to large forest fires. Therefore, more attention should be given to mitigating the anthropogenic emissions in the area for the purposes of promoting air quality.

A biological basis for planned burning

Fires in Victoria have shaped the vegetation for many millennia. Anthropogenic fires have been used to manage the landscape, initially as an agricultural tool, latterly for ecological reasons and as a means of minimizing the damage done by wildfires. Some characteristics of Victoria’s fire planning and management processes are discussed, such as the requirement for maintenance of biodiversity values and the Adaptive Experimental Management approach being followed. Similarly, some of the most critical regeneration characteristics of plants and vegetation types are highlighted and how these affect burning plans. Given the lack of fully-populated data sets various synthetic whole-of-ecosystem approaches are necessary and the derivation and application of one of these (establishment of Maximum and Minimum Tolerable Fire Intervals) is presented. Ecological constraints on existing (fire and fuel) management are discussed and directions for future research and on-going management considered, including the gaps in our current knowledge base.

An alternative fire regime zonation for Canada

The ability of national and multipurpose ecological classification systems to provide an optimal zonation for a fire regime is questionable. Using wildfire (&gt;1 ha) point data for the 1980–99 period, we defined zones with a homogeneous fire regime (HFR) across Canada and we assessed how these differ from the National Ecological Framework for Canada (NEFC) units of corresponding scale, i.e. ecoprovinces. Two HFR zonations were produced through spatially constrained clustering of (i) 1600-km2 cells and (ii) the smallest units of the NEFC system, i.e. ecodistricts, using attributes for natural and anthropogenic fires. Thirty-three HFR zones were identified. HFR zonations showed smaller differences among each other than with NEFC ecoprovinces. Comparisons with ecoprovinces suggested general agreement of generalised fire regime values with HFR zones but with poor zone boundary correspondence. Ecoprovince zonation led to an overgeneralisation of fire regime estimates with less variation captured than by the HFR zonations, especially that using gridded fixed-area cells. Estimates of fire-return interval strongly differed between a priori and HFR zonations. The use of large-scale NEFC units or a zonation using its smallest units may constrain our ability to accurately quantify and portray fire regime variability across the country. The alternative empirical HFR zonation using gridded cells refines the location and nature of fire risk.