Publications - Forest Fires

A comparison of Canadian and Russian boreal forest fire regimes.

Fri, 21 Sep 2012

Boreal forest dynamics are largely driven by disturbance, and fire is a prevalent force of change across the boreal circumpolar region. North American and Eurasian boreal fire regimes are known to be very different but there are few quantitative comparison studies. Russian and Canadian boreal fire regimes are compared using fire weather, fire statistics, fire behaviour, and C emissions data from two large study areas. Fuel consumption, head fire intensity, and C emissions were modelled using fire weather data, fuels data and burned area polygons for all large (200+ ha) fires that occurred in the study areas during 2001–2007. Fire behaviour and C emissions of each large fire were simulated with the Canadian Fire Effects Model (CanFIRE) using fuel type and fuel load data of the burned areas, and Canadian Forest Fire Weather Index System parameters, as interpolated to the fire from the weather station network on the average active fire date. In the Russian study area located in central Siberia, there was an annual average of 1441.9 large fires per 100 M ha of forest land that burned 1.89 M ha (average large fire size = 1312 ha, mean fire return interval = 52.9 years) with an average fire intensity of 4858 kW m1. In the western Canada study area, there was an annual average of 93.7 large fires per 100 M ha of forest land that burned 0.56 M ha of forest (average large fire size = 5930 ha, mean fire return interval = 179.9 years) with an average fire intensity of 6047 kW m-1. The 2001–2007 fire size distribution and annual area burned in the Canadian study area were very similar to 1970–2009 statistics, although large fire frequency was higher and average large fire size was smaller. Similar long-term fire statistics for Russia currently do not exist for comparison. The C emissions rate (t ha-1 of burned area) was 53% higher in the Canadian study area due to higher pre-burn forest floor fuel loads and higher fuel consumption by crown fires. However, the Russian study area had much higher total C emissions (per 100 M ha of forest area) because of greater annual area burned. The Russian C emissions estimate in this study is likely conservative due to low forest floor fuel load estimates in available datasets. Fire regime differences are discussed in terms of fuel, weather, and fire ecology.

Afforestation opportunities when stand productivity is driven by a high risk of natural disturbance: a review of the open lichen woodland in the eastern boreal forest of Canada.

Fri, 11 Jan 2013

Afforestation has the potential to offset the increased emission of atmospheric carbon dioxide and has therefore been proposed as a strategy to mitigate climate change. Here we review the opportunities for carbon (C) offsets through open lichen woodland afforestation in the boreal forest of eastern Canada as a case study, while considering the reversal risks (low productivity, fires, insect outbreaks, changes in land use and the effects of future climate on growth potential as well as on the disturbances regime). Our results suggest that : (1) relatively low growth rate may act as a limiting factor in afforestation projects in which the time available to increase C is driven by natural disturbances; (2) with ongoing climate change, a global increase in natural disturbance rates, mainly fire and spruce budworm outbreaks, may offset any increases in net primary production at the landscape level; (3) the reduction of the albedo versus increase in biomass may negatively affect the net climate forcing; (4) the impermanence of C stock linked to the reversal risks makes this scenario not necessarily cost attractive. More research, notably on the link between fire risk and site productivity, is needed before afforestation can be incorporated into forest management planning to assist climate change mitigation efforts. Therefore, we suggest that conceivable mitigation strategies in the boreal forest will likely have to be directed activities that can reduce emissions and can increase C sinks while minimizing the reversal impacts. Implementation of policies to reduce Greenhouse Gases (GHG) in the boreal forest should consider the biophysical interactions, the different spatial and temporal scales of their benefits, the costs (investment and benefits) and how all these factors are influenced by the site history.

Charred particle analyses.

Fri, 26 Apr 2013

Distribution patterns of three long-horned beetles (Coleoptera: Cerambycidae) shortly after fire in boreal forest: adults colonizing stands versus progeny emerging from trees.

Tue, 05 Feb 2013

We identified the factors that affect the early colonization of burned stands by adults and the progeny surviving in fire-killed black spruce trees for three cerambycid beetles: Acmaeops proteus proteus (Kirby), Acmaeops pratensis (Laicharting), and Monochamus scutellatus scutellatus (Say) (Coleoptera: Cerambycidae) in the northern Canadian boreal forest. Furthermore, we measured if progeny emerging from burned trees was related to patterns of adults captured in traps the same year as the fire. Fire severity at the stand and landscape scales were the most important predictors for colonizing adults. Except for A. pratensis, thick-barked and lightly burned trees positively influenced the occurrence of surviving progeny at the tree level. Last-instar larvae of A. pratensis emerged from burned trees more often in severely burned landscapes. This may result from biotic interactions with intraguild species or predators. With the exception of A. pratensis, variables affecting the postfire abundance and occurrence pattern of adults were strikingly different from progeny emerging after fire. Progeny emerging from burned trees was almost exclusively related to tree- or stand level characteristics, whereas colonizing adults were correlated with variables measured at various spatial scales, and most often at the landscape scale. Moreover, A. proteus proteus and M. scutellatus scutellatus adults were more common in severely burned landscapes, although their progeny emerged more often in lightly or moderately burned trees. Host selection behavior within stands (e.g., host acceptance) by colonizing adults or host suitability for the larvae might have caused this discrepancy.

Fire in managed forests in eastern Canada: Risks and options.

Tue, 21 May 2013

In this era of climate change, understanding past and predicting future fire activity are scientific challenges that are central to the development of sustainable forest management practices and policies. Such objectives, however, are difficult to achieve for several reasons. Uncertainties about future fire activity can be superimposed on the short time period covered by existing meteorological data and fire statistics, from which a historical range of variability can be determined. Regional fire activity is also tremendously variable over time, such that contemporary fire records cannot provide information on the full range of fire activity variability a given forest experienced and adapted to. This factor is increasingly important when it comes to determining the resilience of boreal forests to changes in climate and disturbance regimes. In this paper, we present a synthesis of past, present and future trends in seasonal fire danger and fire activity based on data gathered in eastern Canadian boreal forests over the last 20 years, and we provide a critical assessment of the ability to conduct sustainable forest management over the 21st century. The data synthesis provides compelling evidence of a synchronous pattern of decreasing fireconducive climatic conditions and activity of large fire seasons over the last 2000 years in the eastern coniferous boreal forest. Model simulations suggest that the climate will become drier in upcoming decades, driving future fire activity close to the upper bound of the pre-industrial range of variability. The effects of increasing fire incidence cumulated with forest harvesting may thus pose a risk to forest resilience in the future. This ecological knowledge should help us to define forest management strategies and practices considering future fire activity changes forecasted under climate change. Development of alternative silvicultural interventions that would emulate secondary disturbances (e.g. wind, insects) rather than fire would be necessary to maintain pre-industrial forest characteristics (e.g. composition and age class distribution), and associated forest resilience.

Global wildland fire season severity in the 21st century.

Thu, 04 Apr 2013

We used Cumulative Severity Rating (CSR), a weather-based fire danger metric, to examine the potential influence of climate change on global fire season severity. The potential influence of climate change on fire season length was also addressed. We used three General Circulation Models (GCMs) and three emission scenarios to calculate the CSR and fire season length for mid-century (2041–2050) and late century (2091–2100) relative to the 1971–2000 baseline. Our results suggest significant increases in the CSR for all models and scenarios. Increases were greatest (more than three times greater than the baseline CSR) for the Northern Hemisphere at the end of the century. Fire season length changes were also most pronounced at the end of the century and for northern high latitudes where fire season lengths will increase by more than 20 days per year. The implications from this study are that fire seasons will be more severe in future and that conventional fire management approaches may no longer be effective.

In Brief from the Canadian Forest Service, Laurentian Forestry Centre. No. 32.

Thu, 07 Feb 2013

Modelling wood density within the stem: a journey through space and time.

Native and exotic poplars: a fruitful marriage?

Fires and springtime temperatures: a matter of size.

What habitat do chanterelles seek out in the boreal forest?

Spruce budworm outbreaks: heading north.

Poplar leaf rust: resistance triggers unmasked.

In Brief from the Canadian Forest Service, Laurentian Forestry Centre. No. 33.

Mon, 18 Mar 2013

Partial cutting in the boreal forest: the right choice for biodiversity.

Fire regimes have an influence on forest succession.

Heat causes release of CO² from forest soil.

Forest biomass: A good choice, if you know how to count.

Is there competition or mutual support between species in mixed stands?

Impact of biomass harvesting in boreal and temperate forests.

Introducing two indicators for fire risk consideration in the management of boreal forests.

Fri, 11 Jan 2013

When forest fires are taken into account during timber supply analyses, planned harvest rates are necessarily reduced to prevent potential timber shortages due to future forest fires. Because fire events are highly unpredictable, forest managers are reluctant to proactively reduce harvest targets, as it results in an immediate revenue loss. We explored a simple but proactive way of including the risks and uncertainties of fire in forest management planning through the identification of low productivity forest areas most vulnerable to fire in two different boreal forest zones. Site index and relative density index were used to estimate the time required to reach different harvesting thresholds based on stem size and tree density. We varied the production objective by using three different thresholds of minimum stem size (dm³/tree) and stand yield (m³/ha) (50 dm³/tree – 50m³/ha, 70 dm³/tree – 70m³/ha, 90dm³/tree – 90m³/ha). We estimated the time required to reach these thresholds and the proportion of forest zone that could exceed them. Fire cycle length was then used to assess the survival likelihood (probability of reaching the threshold at the stand scale when considering fire risk). An alternative rate of return was also used as an indicator of profit exposure to fire risk. When survival likelihood and alternative rate of return are considered jointly with time-declining interest rates, minimum survival likelihoods need to be higher for longer fire cycles. The proportion of stands vulnerable to fire served to decide whether or not to include fire risk into strategic planning. The identification of major break points in the vulnerability assessment also helped to decide which minimum harvesting threshold is appropriate as a function of the productivity characteristics and fire cycle of the forest under management.

Les Brèves du Service canadien des forêts, Centre de foresterie des Laurentides. No 32.

Thu, 07 Feb 2013

Modelling wood density within the stem: a journey through space and time.

Native and exotic poplars: a fruitful marriage?

Fires and springtime temperatures: a matter of size.

What habitat do chanterelles seek out in the boreal forest?

Spruce budworm outbreaks: heading north.

Poplar leaf rust: resistance triggers unmasked.

Les Brèves du Service canadien des forêts, Centre de foresterie des Laurentides. No 33.

Mon, 18 Mar 2013

Partial cutting in the boreal forest: the right choice for biodiversity.

Fire regimes have an influence on forest succession.

Heat causes release of CO² from forest soil.

Forest biomass: A good choice, if you know how to count.

Is there competition or mutual support between species in mixed stands?

Impact of biomass harvesting in boreal and temperate forests.

A lightning fire prediciton system. Frontline Express 60.

Mon, 01 Oct 2012

In Canada an average of 8,000 forest fires occur each year and the area burned ranges from 0.7 to 7.6 million hectares/year. Average suppression costs are $500 million to $1 billion annually. While just under 50% of fires occur from lightning, they lead to 85% of the area burned. This is largely due to the number of lightning fires that occur in remote locations. Although some of these fires are left to burn to allow natural renewal of the forest, those that require suppression may be difficult to control due to delays in their detection and the arrival of fire fighting resources, allowing the fires to grow and reach higher intensities. Lightning fires also tend to occur in clusters, with as many as 50 to 100 or more igniting in a single day in some provinces, which can strain initial attack systems. With the warming of the atmosphere expected with climate change, an increase in lightning activity can be expected and that coupled with potentially increased receptivity of fuels to ignition means that lightning fires will increasingly influence the landscape and forest fire management activities. While fire suppression is a provincial or territorial responsibility, the Canadian Forest Service (CFS) has developed effective tools that allow provincial fire agencies to better plan for fire and enhance protection of areas of concern. One such tool is the Canadian Forest Fire Danger Rating System (CFFDRS), the result of a Canadian research program that began in the late 1920s, and which is currently used operationally throughout Canada and in a growing number of countries around the world. It helps fire management agencies by providing outputs that assist them in estimating when and where fires are expected to occur each day. The system takes into account factors such as weather, fuel and topography to estimate ease of ignition and difficulty of control and is used as a guide in a wide variety of fire management activities. CFS scientists continually work to improve the system and recently have enhanced it to more accurately predict lightning-caused fire probability.

A mathematical model for predicting the maximum potential spotting distance from a crown fire.

Mon, 18 Jun 2012

A mathematical model is presented for predicting the maximum potential spot fire distance from an active crown fire. This distance can be estimated from the height of the flame above the canopy top, wind speed at canopy-top height and final firebrand size (i.e. its residual size on alighting), represented by the diameter of a cylinder of woody char. The complete model system comprises several submodels or components: a model for the height and tilt angle of the windblown line-fire flame front, a simplified two-dimensional model of the wind-blown buoyant plume from the fire, an assumed logarithmic wind speed variation with height, and an empirically based model for the burning rate of a wooden cylinder in cross flow, which represents the firebrand. The trajectory of the burning particle is expressed analytically from where it leaves the lower boundary of the plume until it enters the canopy top. Adding the horizontal distance of this flight to that of the point where the particle can no longer be held aloft by the plume flow gives a spotting range that depends on the final diameter of the burning particle. Comparisons of model output with existing information on crown fire spotting distances has initially proved encouraging but further evaluation is warranted.

An alternative fire regime zonation for Canada.

Fri, 11 Jan 2013

The ability of national and multipurpose ecological classification systems to provide an optimal zonation for a fire regime is questionable. Using wildfire (.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.

Assessment of boreal forest historical C dynamics in the Yukon River Basin: relative roles of warming and fire regime change

Fri, 21 Dec 2012

Carbon (C) dynamics of boreal forest ecosystems have substantial implications for efforts to mitigate the rise of atmospheric CO₂ and may be substantially influenced by warming and changing wildfire regimes. In this study we applied a large-scale ecosystem model that included dynamics of organic soil horizons and soil organic matter characteristics of multiple pools to assess forest C stock changes of the Yukon River Basin (YRB) in Alaska, USA, and Canada from 1960 through 2006, a period characterized by substantial climate warming and increases in wildfire. The model was calibrated for major forests with data from long-term research sites and evaluated using a forest inventory database. The regional assessment indicates that forest vegetation C storage increased by 46 Tg C, but that total soil C storage did not change appreciably during this period. However, further analysis suggests that C has been continuously lost from the mineral soil horizon since warming began in the 1970s, but has increased in the amorphous organic soil horizon. Based on a factorial experiment, soil C stocks would have increased by 158 Tg C if the YRB had not undergone warming and changes in fire regime. The analysis also identified that warming and changes in fire regime were approximately equivalent in their effects on soil C storage, and interactions between these two suggests that the loss of organic horizon thickness associated with increases in wildfire made deeper soil C stocks more vulnerable to loss via decomposition. Subbasin analyses indicate that C stock changes were primarily sensitive to the fraction of burned forest area within each subbasin and that boreal forest ecosystems in the YRB are currently transitioning from being sinks to sources at 0.7% annual area burned. We conclude that it is important for international mitigation efforts focused on controlling atmospheric CO₂ to consider how climate warming and changes in fire regime may concurrently affect the CO₂ sink strength of boreal forests. It is also important for large-scale biogeochemical and earth system models to include organic soil dynamics in applications to assess regional C dynamics of boreal forests responding to warming and changes in fire regime.

Brûlage dirigé dans l'écosystème de la prairie à herbes hautes. Nouvelles Express 55.

Wed, 07 Mar 2012

L’écosystème de la prairie à herbes hautes est un des écosystèmes les plus menacés au Canada. Il est caractérisé par des herbes atteignant trois mètres de haut et par une variété de fleurs et d’animaux sauvages, y compris de nombreuses espèces en péril. De cetécosystème qui s’est déjà étendu sur 1 000 km2 au sud de l’Ontario, il ne reste maintenant que 3 % de ce territoire réparti en petites parcelles morcelées. Ces zones, entre la rivière Trent et Windsor, représentent l’étendue la plus à l’est de l’écosystème au Canada. Une cause majeure du déclin de cet écosystème était la pratique d’élimination des incendies au siècle dernier; de fréquents incendies sont nécessaires pour encourager la production de semences et pour empêcher l’empiétement desplantes ligneuses. Les efforts de restauration des 20 dernières années ont intégré un programme de plus en plus actif de brûlage dirigé exécuté par un éventail croissant d’intervenants. Des scientifiques spécialisés dans les incendies auprès du Service canadien des forêts (SCF) et reconnus mondialement pour leur expertise en création de système de prévision du comportement des incendies ont participé à la création de nouveaux modèles de prévision du comportement des feux d’herbe. Ces nouveaux modèles cherchent à prédire avec plus de précision que le modèle actuel la vitesse de propagation pour le type de combustible de l’écosystème de la prairie à herbes hautes. Le Field Guide to Predicting Fire Behaviour in Ontario’s Tallgrass Prairie (Manuel de terrain pour la prévision du comportement des incendies de forêt dans la prairie à herbes hautes de l’Ontario) fournira aux intervenants du brûlage les meilleures connaissances scientifiques et les meilleurs outils disponibles les aidant à préparer des plans de brûlage et à prendre des décisions touchant le comportement escompté des incendies pour toute journée de brûlage possible, minimisant ainsi les risques pour le public et pour les propriétés dans le secteur.

CANFIRE Model. Frontline Express 62.

Mon, 01 Oct 2012

Forest fires are a critical element of healthy forest ecosystems across Canada. An average of 8,000 forest fires occur each year, while the area burned ranges from 0.7 to 7.6 million ha/year. In boreal forests in particular, fire plays an essential role in renewal, however these fires are frequently large, with rapid rates of spread and high fuel consumption. Canadian Forest Service (CFS) fire scientists recently developed the CanFIRE model, which is a useful tool in improving our understanding of forest fire behaviour, the impact of fires on the landscape and their contribution to Canada’s carbon emissions. This information is essential for international reporting under the United Nations Framework Convention on Climate Change. In addition, the model is useful for predicting how fire patterns will change in the future, with a warming climate. Currently, average annual suppression costs range from $500 million to $1 billion, but this cost is expected to rise with predicted increasing fire activity and subsequent threats to values at risk.

Climate change and disruptions to global fire activity.

Thu, 14 Jun 2012

Future disruptions to fire activity will threaten ecosystems and human well-being throughout the world, yet there are few fire projections at global scales and almost none from a broad range of global climate models (GCMs). Here we integrate global fire datasets and environmental covariates to build spatial statistical models of fire probability at a 0.58 resolution and examine environmental controls on fire activity. Fire models are driven by climate norms from 16 GCMs (A2 emissions scenario) to assess the magnitude and direction of change over two time periods, 2010–2039 and 2070–2099. From the ensemble results, we identify areas of consensus for increases or decreases in fire activity, as well as areas where GCMs disagree. Although certain biomes are sensitive to constraints on biomass productivity and others to atmospheric conditions promoting combustion, substantial and rapid shifts are projected for future fire activity across vast portions of the globe. In the near term, the most consistent increases in fire activity occur in biomes with already somewhat warm climates; decreases are less pronounced and concentrated primarily in a few tropical and subtropical biomes. However, models do not agree on the direction of near-term changes across more than 50% of terrestrial lands, highlighting major uncertainties in the next few decades. By the end of the century, the magnitude and the agreement in direction of change are projected to increase substantially. Most far-term model agreement on increasing fire probabilities (;62%) occurs at mid- to high-latitudes, while agreement on decreasing probabilities (;20%) is mainly in the tropics. Although our global models demonstrate that long-term environmental norms are very successful at capturing chronic fire probability patterns, future work is necessary to assess how much more explanatory power would be added through interannual variation in climate variables. This study provides a first examination of global disruptions to fire activity using an empirically based statistical framework and a multi-model ensemble of GCM projections, an important step toward assessing fire-related vulnerabilities to humans and the ecosystems upon which they depend.

Considerations for modeling burn probability across landscapes with steep environmental gradients: an example from the Columbia Mountains, Canada.

Tue, 18 Dec 2012

Fire and land management in fire-prone areas can be greatly enhanced by estimating the likelihood of fire at every point on the landscape. In recent years, powerful fire simulation models, combined with an in-depth understanding of an area’s fire regime and fire environment, have allowed forest managers to estimate spatial burn probabilities. This study describes a methodology for selecting input data and model parameters when creating burn probability maps in difficult-to-model areas and reports the results of a case study for a large area of the Columbia Mountains, British Columbia, Canada. In addition to having particularly mountainous topography, the study area is covered by vegetation types that are poorly represented in fire behavior systems, even though these vegetation types have experienced considerable (if highly irregular) fire activity in premodern times (before 1920). Parameterization of the fire environment for simulation modeling was accomplished by combining various types of fire information (e.g., fire history studies, reconstructed fire climatologies), new technologies (high-resolution remotely sensed data, wind flow modeling), and—a must in data-limited areas—ample expert advice. In this study, we made extensive use of personal accounts from experienced fire behavior officers for the creation of model inputs. Despite difficulties in validating outputs of burn probability models, the multisource model-building approach described here provides a conservative, yet informative, means of estimating the likelihood of fire. Due to the data-intensive nature of the modeling and paucity of input data, an argument is made that modelers must focus on the inputs that are the most influential for their study area.

Detecting post-fire salvage logging from Landsat change maps and national fire survey data

Wed, 15 Feb 2012

In Canadian boreal forests, wildfire is the predominant agent of natural disturbance often with millions of hectares burning annually. In addition to fire, nearly one quarter of Canada's boreal forest is also managed for industrial wood production. Post-fire logging (or salvage harvesting) is increasingly used to minimize economic losses from fire, notwithstanding that the ecological impacts of successive disturbance events remain poorly understood. Improved monitoring and management of post-fire environments will require new information regarding the location and timing of past operations. In this paper we present and evaluate a data integration approach for detecting spatial and temporal trends in post-fire logging. Here we utilize a series of maps relating timing and extent of burned area (from the Canadian Large Fire Database) and year of harvest (from Landsat change detection) to identify occurrences of post-fire logging between 1987 and 2008 for a portion of boreal forest located in central Saskatchewan, Canada. Using a design-based, stratified random sampling framework we found that 68% (95% confidence interval (CI) [53 to 84%]) of the detected post-fire logging was correctly classified, such that both fire and clearcutting disturbances were positively verified by the reference data. The majority of map error resulted from spectral confusion between harvested areas and rock outcroppings exposed by fire and from mislabeling harvested unburned islands as post-fire logging. To add further confidence to our classification accuracy, we also found that mapped post-fire logging displayed similar temporal trends over a ten year period as salvage volume reported for a forest management area partially contained within the study area. Based upon the significant relationship between these estimates (r = 0.97, p < 0.001) and the good degree of observed map accuracy, we believe that the presented approach offers a viable and flexible option for characterizing the spatial and temporal dynamics of post-fire logging in boreal forests. Maps which reliably identify areas of post-fire logging stand to improve our capacity to manage and model the ecological impacts associated with multiple disturbance events.

Differential effects of post-fire habitat legacies on beta diversity patterns of saproxylic beetles in the boreal forest.

Fri, 08 Mar 2013

Fire-generated mosaics of habitat legacies such as dead and dying trees are key structural components in boreal forest ecosystems that support diverse saproxylic beetles. Our study sought to elucidate the spatial pattern of community composition (beta diversity) of saproxylic beetles along gradients of post-fire habitat legacies (tree species composition, tree size [dbh], and burn severities) and geographical distance. For 2 y, we reared saproxylic beetles from 360 logs retrieved from 72 sites in burned forests. Tests were performed to explain the overall beta diversity (β_sor) by partitioning it into its 2 components: the “species spatial turnover” due to species replacement (β_sim) and the “richness-driven” beta diversity due to species richness differences (β_rich). Variations in tree species, tree size, and burn severity had significant effects on overall beta diversity (β_sor) of saproxylic beetles; these effects varied according to the differential influence of these factors on the 2 distinct components of beta diversity. Tree composition had notable effects on species spatial turnover (β_sim), for which saproxylic species composition differed between jack pine and black spruce, and it was more variable between jack pine sites than between black spruce sites. On the other hand, variation in tree size was primarily responsible for the richness-driven beta diversity component (β_rich), which was highest between the smallest and largest dbh groups and lowest between largest and mid-sized trees. Similarly, richness-driven composition differed significantly across severity gradients and was highest across low to high severity and lowest between low-severity stands. Broader geographical distance per se did not affect compositional patterns of saproxylic beetles, yet the landscape context could have some effect. These results could have crucial implications for post-fire management, which also aims to efficiently conserve saproxylic beetles. The significant spatial turnover in saproxylic composition between black spruce and jack pine and the underlying host-tree specificity suggest that a mosaic of both tree species should be maintained in the landscape. The richness-driven beta diversity pattern along the tree size and severity gradients implies that it may be necessary to prioritize the most species-rich classes, such as larger trees with lower severity burns, but with qualifications to cater also for species displaying idiosyncratic distributions.

Effects of habitat characteristics and interspecific interactions on co-occurrence patterns of saproxylic beetles breeding in tree boles after forest fire: null model analyses.

Wed, 14 Mar 2012

It is often suggested that habitat attributes and interspecific interactions can cause non-random species cooccurrence patterns, but quantifying their contributions can be difficult. Null models that systematically exclude and include habitat effects can give information on the contribution of these factors to community assembly. In the boreal forest, saproxylic beetles are known to be attracted to recently burned forests where they breed in dead and dying trees. We examined whether species co-occurrences of saproxylic beetles that develop in, and emerge from, boles of recently burned trees show non-random patterns. We also estimated the extent to which both the post-fire habitat attributes and interspecific interactions among beetles contribute to such patterns. We sampled tree boles encompassing key attributes (tree species, tree size/dbh and burn severity) that are thought to characterize species–habitat associations of saproxylic beetles, a proposition that we tested using indicator species analysis. Two null models with no habitat constraints (“unconstrained”) indicated that a total of 29.4% of the species pairs tested had significant co-occurrence patterns. Habitat-constrained null models indicated that most of the detected species aggregations (72%) and segregations (59%) can be explained by shared and distinct species–habitat relationships, respectively. The assembly pattern was also driven by interspecific interactions, of which some were modulated by habitat; for example, predator and prey species tended to co-occur in large-sized trees (a proxy of available bark/wood food resource primarily for the prey). In addition, some species segregation suggesting antagonistic, competitive, or prey–predator interactions were evident after accounting for the species’ affinities for the same tree species. Overall, our results suggest that an intimate link between habitat and interspecific interactions can have important roles for community assembly of saproxylic assemblages even following disturbance by fire. We also show that a systematic application of null models can offer insight into the mechanisms behind the assembly of ecological communities.

Examining the utility of the Canadian Forest Fire Weather Index System in boreal peatlands.

Thu, 12 Jan 2012

The Duff Moisture Code (DMC) and Drought Code (DC) components of the Canadian Forest Fire Weather Index (FWI) System are used by fire managers to assess the vulnerability of organic soils to ignition and depth of burn despite being developed for upland soils. Given the need to assess wildfire risk in peatlands, we compared the DMC and DC in eight peatlands located in five regions in boreal Canada with water table position (WT) and surface volumetric moisture content (VMC). The slope of the change in WT and DC relationship ranged greatly (–0.01 to –0.11 cm) between sites and years likely due to differences in site-specific peat properties, catchment water supply, and presence of seasonal ice. A DC of 400, which has been associated with wildfire vulnerability in uplands, corresponded to a seasonal drop in WT in the range of 4–36 cm. The slopes of the relationships between DMC and DC with 5 and 15 cm VMC also varied greatly between sites. Our findings suggest that these FWI components are suitable for predicting the general moisture status and fire danger in boreal peatlands. However, there is a need for a modified DC for specific peat types to indicate when the WT has reached a critical depth upon which fire danger increases. We also present a suggested framework for the development of a new peat moisture code within the FWI.

Expected effects of climate change on forest disturbance regimes in British Columbia

Mon, 02 Apr 2012

In this article we summarize the changes to forest disturbance regimes and forest damage that are projected to emerge under a changing climate in British Columbia (BC). We focus on regionally-specific expectations so that land managers can take pro-active steps to avoid or adapt to future conditions. While some projections are based on extrapolations of recent multi-decadal trends, most are based on global climate models (GCMs) that utilize a range of scenarios for possible atmospheric greenhouse gas emission trajectories over the next century. Regardless of the models or emission scenarios used, it is universally expected that BC will experience warmer air temperatures. Projections for precipitation are more variable, ranging from slight decreases in some regions to substantial increases in others, which have different effects on disturbance projections. Forest fires are expected to be more frequent and more intense in the southern half of the province and in the Taiga Plains, but less important in other portions of the province. Forest insects and fungal pathogens are expected to more fully occupy the current range of their host tree species and expand ranges northward and to higher elevations along with their hosts. More frequent and more detrimental pest outbreaks are expected in some regions when several years of favourable weather align, which is more likely under current and projected climate trends. Wind damage, floods, and landslides can be expected to increase on terrain where they are already a risk factor. For many agents of tree mortality, an expansion or shifting of the seasonal window of activity is expected, but these changes vary among regions within BC. The prediction of future forest disturbance regimes is in its infancy, requiring a much more concerted effort in compiling both empirical and simulated data, but managers may wish to adjust plans accordingly where there is consensus among projections.

Feux en milieu périurbain. Nouvelles Express 65.

Thu, 08 Nov 2012