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•We report carbon release from a smouldering wildfire on an afforested peatland.•Fuel moisture indices suggested high peat fire hazard around the time of the burn.•The fire released ...96±15tonnes of carbon per hectare burnt (9.6±1.5kgm−2).•These emissions represent up to 0.3% of that sequestered annually by UK peatlands.•Patterns of peat consumption suggested afforestation may increase the risk of smouldering fires.
Temperate peatlands represent a substantial store of carbon and their degradation is a potentially significant positive feedback to climate change. The ignition of peat deposits can cause smouldering wildfires that have the potential to release substantial amounts of carbon and to cause environmental damage from which ecosystem recovery can be slow. Direct estimates of the loss of carbon due to smouldering wildfires are needed to inform global estimates of the effect of wildfire on carbon dynamics and to aid with national emissions accounting. We surveyed the effect of a severe wildfire that burnt within an afforested peatland in the Scottish Highlands during the summer of 2006. The fire ignited layers of peat which continued to burn as a sub-surface smouldering wildfire for more than a month after the initial surface fire and despite several episodes of heavy rain. The smouldering fire perimeter enclosed an area of 4.1ha. Analysis of weather records showed that the fire coincided with unusually warm, dry conditions and a period when the Canadian Fire Weather Index system predicted both generally high danger conditions (high Fire Weather Index) and low fuel moisture content in deep organic soil layers (high Drought Code values). Remaining peat layers in the burn area had comparatively low fuel moisture contents of ca. 250% dry weight. Within the smouldering fire’s perimeter, mean depth of burn was estimated at 17.5±2.0cm but ranged from 1 to 54cm. Based on field measurements, our estimates suggested that, in total, the smouldering wildfire burnt 773±120t of organic matter corresponding to 396±63t of carbon and a carbon loss per unit area burnt of 96±15tha−1 (9.6±1.5kgm−2). This corresponds to between 0.1% and 0.3% of the estimated total amount of carbon sequestered annually by UK peatlands. Our results also provide circumstantial evidence that afforestation of peatland soils, and associated site preparation, may contribute to an increased risk of peat fires. Smouldering fires are difficult to detect using remotely sensing techniques due to their low temperature and low heat release and the fact that the tree canopy remains intact for months afterwards. If similar smouldering fires are underreported in other temperate, boreal and tropical peatland regions then emissions from peatland burning may well be a substantially greater issue than currently assumed.
Ecological conservation monitoring programmes abound at various organisational and spatial levels from species to ecosystem. Many of them suffer, however, from the lack of details of goal and ...hypothesis formulation, survey design, data quality and statistical power at the start. As a result, most programmes are likely to fail to reach the necessary standard of being capable of rejecting a false null hypothesis with reasonable power. Results from inadequate monitoring are misleading for their information quality and are dangerous because they create the illusion that something useful has been done. We propose that conservation agencies and those funding monitoring work should require the demonstration of adequate power at the outset of any new monitoring scheme.
There is a general consensus that functional traits are reliable indicators of adaptation of organisms to particular environmental characteristics. In this study we relate the combined distributions ...of species traits of plants and animals to disturbance regimes in chestnut forests of southern Switzerland affected by regular winter fires. We used co-inertia analysis for combining the trait response of 471 invertebrate species (117 001 individuals) and 81 plant species at 23 sites with different fire and cutting histories. Trait response was assessed by calculating the variation in weighted mean traits averaged over the communities and by using mean traits in multivariate analyses. The analysis showed a strong association between plant and animal traits under fire constraints (Monte-Carlo test, p=0.0045). Plants and animal distributions show parallel trends in responses to fire which selects traits relating to persistence (ability to survive), resilience (ability to recover) and mobility. Warmth-demanding insects, herbivores, flying carnivores and pollinators were associated with recent fires, as were annual, ruderal and light-demanding plant species with long flowering duration. Small arthropods feeding on dead wood and those with narrow habitat requirements were associated with low fire frequency and unburnt sites, as were competitive plants with large seeds favoring moist sites. The spatial association between plant and animal traits reflected adaptations that promote survival in the disturbance regime, while the disturbance acts as an environmental filter on the distribution and assemblage of the trait values within communities. This combined analysis of plant and invertebrate traits distributions illustrates how community and ecosystem responses can be monitored and the results generalized across localities and disturbance types. Analyses of traits that cross trophic levels provide powerful and promising tools for validating management procedures and controlling ecosystem functions.
Fire is widely used as a traditional habitat management tool in Scotland, but wildfires pose a significant and growing threat. The financial costs of fighting wildfires are significant and severe ...wildfires can have substantial environmental impacts. Due to the intermittent occurrence of severe fire seasons, Scotland, and the UK as a whole, remain somewhat unprepared. Scotland currently lacks any form of Fire Danger Rating system that could inform managers and the Fire and Rescue Services (FRS) of periods when there is a risk of increased of fire activity. We aimed evaluate the potential to use outputs from the Canadian Fire Weather Index system (FWI system) to forecast periods of increased fire risk and the potential for ignitions to turn into large wildfires. We collated four and a half years of wildfire data from the Scottish FRS and examined patterns in wildfire occurrence within different regions, seasons, between urban and rural locations and according to FWI system outputs. We used a variety of techniques, including Mahalanobis distances, percentile analysis and Thiel-Sen regression, to scope the best performing FWI system codes and indices. Logistic regression showed significant differences in fire activity between regions, seasons and between urban and rural locations. The Fine Fuel Moisture Code and the Initial Spread Index did a tolerable job of modelling the probability of fire occurrence but further research on fuel moisture dynamics may provide substantial improvements. Overall our results suggest it would be prudent to ready resources and avoid managed burning when FFMC > 75 and/or ISI > 2.
Background
Prescribed burning plays an important role in the management of many ecosystems and can also be used to mitigate landscape-scale fire risk. Safe and effective application of prescribed ...fire requires that managers have a robust understanding of potential fire behavior in order to decide on the appropriate tools and tactics for any burning operation. Shrubland ecosystems, including heaths and moors, are known to exhibit intense fire behavior under marginal burning conditions under which fire would not be expected to spread in other vegetation types. This makes developing fire behavior predictions for such systems important. Traditional managed burning is widely used as a tool in
Calluna vulgaris
(L.) Hull-dominated heath and moorland landscapes in northwest Europe, but in some regions, especially the United Kingdom, there is significant debate over fire use. Despite the controversy, there is general agreement on the need to (1) understand relationships between fuel structure and potential fire behavior, and (2) improve burning practice to optimize potential trade-offs between different ecosystem services. Our aim was to provide knowledge to improve management practice by developing models of potential fireline intensity and flame length. We conducted 27 burns in three developmental stages of
Calluna
with different stand structures and estimated fireline intensity, flame length, flame height, and flame angle. Flame properties were assessed using photographs and visual observation. We evaluated our models using a participatory research approach for which conservation and land managers submitted basic observations on fire behavior and fire weather for their burns.
Results
Fireline intensity and flame height increased significantly across age-related
Calluna
phases. Regression modeling revealed that fireline intensity could be adequately estimated by a combination of fuel height and wind speed, with taller fuels and higher wind speeds related to more intense fires. Predictions were, however, improved by accounting for live fuel moisture content. Flame length and height were modeled as a function of fireline intensity using standard approaches, but adequately performing models for flame angle could not be established. Evaluation data provided by land managers was noisy, but their qualitative assessments of fire behavior and estimates of flame length were significantly correlated with predictions from our models.
Conclusions
Fire intensities and flame properties seen in northern
Calluna
heathlands are similar to those encountered in shrublands associated with climates and fuels more commonly perceived as representing high fire danger. The results demonstrated that our models perform tolerably well although there is substantial uncertainty in their predictions. The models were used to develop a fire behavior nomogram that can provide an indication of potential fireline intensity and flame length prior to commencing a burn.
1. Calluna-dominated heaths occur throughout Europe but are in decline across their range. There is growing interest in using prescribed burning for their management, but environmental and social ...change will impact future fire regimes. Understanding fire behaviour is vital for the sustainable use of fire, but no robust models exist to inform management. 2. Shrub fuels display complex fire behaviour. This is particularly true in UK moorlands which are unusual in their fuel structure and moisture regime, being dominated by live fuel and an oceanic climate. 3. We burnt 27 experimental fires in the Scottish uplands during the legal burning season using a replicated experimental design. Plots were assigned to one of three commonly identified growth phases. We estimated a range of prefire fuel characteristics, including heterogeneity in fuel structure. We recorded wind speed and direction and estimated rate of spread (RoS). 4. Redundancy analysis was used to investigate the relationship between fire behaviour parameters as a whole and control variables. Fuel structure and heterogeneity, wind speed and canopy fuel moisture content were strongly related to variation in fire behaviour. 5. Best subsets regression was used to generate models of fire spread based on wind speed, vegetation height, canopy fuel moisture and an index of fuel heterogeneity. RoS was determined largely by wind speed, but this interacted strongly with vegetation structure. Changes in fuel horizontal continuity and vertical structure reduced rates of spread in low wind speeds. 6. Synthesis and applications. Live fuel moisture and fuel heterogeneity play an important role in dampening fire behaviour, aspects of shrub fuels that have previously not been examined in detail. Careful use of fire for moorland management increases habitat diversity and creates fire-safe landscapes. Escaped prescribed fires burn large areas, homogenize landscapes and have severe impacts on ecosystem services. The complex relationship between fuel structure and wind speed implies that changes in behaviour can be rapid and unexpected. Models can be used to assess fire hazard prior to prescribed burning and to choose fuels that can be burnt safely under prevailing or forecast conditions.
Managed and wild fires play a significant role in the ecology of heathlands in the UK but we currently have little ability to forecast fire behaviour or the likelihood of accidental wildfires. Like ...many shrubland fuel types, heathlands display significant structural complexity and the role of different fuel components in governing flammability has not been clear. Using a series of small, field-based ignition tests, we demonstrate the critical importance of the moisture content of dead fine fuels in the lower canopy for determining when sustaining fires in the vegetation canopy can develop. At moisture contents above c. 70% both spot and line ignitions failed but where moisture contents were less than c. 60% fires developed rapidly. The initial rate of spread of successful ignitions was primarily controlled by the moisture content of the lower canopy and the moss/litter layer. Models that predict the moisture content of elevated dead fuels and the moss litter layer are urgently needed in order to protect heathlands from wildfire and to allow forecasts of the suitability of conditions for prescribed burning to be developed.
1. Pitfall trapping is one of the most widely used arthropod sampling techniques. However, relative species abundance in pitfall trap catches differs from that found using quadrat samples. This ...difference, here termed bias, reflects the fact that pitfall trap catch is influenced not only by abundance but also by other factors, including activity, which may be linked to body size. Here, we investigate whether the bias affecting pitfall trap catches of a particular species is related to the typical body mass of individuals of that species. 2. Data were extracted from five studies where pitfall trapping bias was quantified and covered 32 species of spiders and carabid beetles. Bias was expressed as the ratio of biomass captured by pitfall traps to that measured by quadrat counts (four field studies), or as the product of mean speed of movement and probability of capture per trap encounter, at standard density (one laboratory study). 3. Pitfall trapping bias and body mass were strongly related on a log–log scale, with log(body mass) explaining 78% of the variation in log(bias) (P < 0.0001). There was no significant effect of arthropod group (spiders, carabids) or study location (field, laboratory). 4. A method is proposed to correct pitfall catches of each of a group of species, based on the typical body mass of an individual of each species. This approach may remove much of the bias in pitfall trap data and so improve the value of this type of data in studies of arthropod communities.
1. Upland heaths in the UK are of significant conservation importance. Large areas are managed through prescribed burning to improve habitat and grazing for red grouse Lagopus lagopus scoticus, deer ...Cervus elaphus and sheep Ovis aries. Previous research has identified trends in vegetation development following burning, but has not linked this to variation in fire behaviour and severity. 2. We burned 15 experimental fires on an area of Calluna vulgaris-dominated moorland, and recorded pre- and post-fire vegetation structure and composition, fire behaviour characteristics, and several 'proxy measures' of fire severity. 3. We distinguished measures of fire severity, describing the immediate physical effects of burning, from the long-term ecosystem responses of substrate development and Calluna regeneration. Proxy measures of fire severity did not relate strongly to fire behaviour or ecosystem response. 4. Post-fire regeneration was strongly linked to stand age and post-fire substrate type. Fire behaviour and severity had little effect, though fire-induced ground-surface heating may promote Calluna seedling establishment. Vegetative regeneration of Calluna was extremely poor in older stands, as was seedling establishment in areas where the post-fire substrate was dominated by live or dead pleurocarpous moss mats. 5.Synthesis and applications. Significant nonlinearities exist in fire severity on heathlands, with step changes related to the depth and moisture content of moss/litter layers and peat. Younger stands, less than c. 30 cm tall, should be the focus of management if the objective is to maximize Calluna regeneration. Burning older and uneven-aged stands is discouraged except for the purposes of fire hazard management. Managers should develop landscape-level burn plans to target burning effectively and create diverse fire regimes.
▶ Vegetation pattern strongly influenced patterns of shrub defoliation by sheep. ▶ Increased heterogeneity seemed to increase resistance of the less preferred species. ▶ Increasing vegetation ...heterogeneity reduces the usefulness of area-based stocking rates to achieve desired vegetation.
In a three-year grazing experiment, three sheep stocking rate treatments were applied to six plots, each containing a natural dwarf-shrub:grass mosaic. Defoliation of the dwarf-shrub, heather (
Calluna vulgaris), was recorded using a spatially-explicit sampling design providing information across multiple spatial scales. Heather defoliation by sheep across the dwarf-shrub:grass mosaics was not homogeneous, but was strongly influenced by the pattern of the preferred vegetation type (grass). While previous studies found that heather defoliation declines with increasing distance from the preferred forage, grass, this experiment showed that the spatial gradient of heather defoliation away from the edge is also affected by the local grazing pressure which is strongly influenced by the local vegetation heterogeneity. Results indicate that the greater the habitat heterogeneity, the more inappropriate a simple vegetation-based stocking rate will be in achieving a desired vegetation condition. The findings support the hypothesis that increased heterogeneity of grass:dwarf-shrub mosaics leads to increased resistance to herbivory, as herbivore impacts are dispersed across the greater total area of ‘impact zone’. The results also highlight the importance of understanding the contrasting spatial patterns of trampling and defoliation impacts, differences which can be further enhanced with increasing heterogeneity of the vegetation.
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