Flammability of tropical grasses: Towards a functional ecology of fire in savannas

Fire frequency affects fire behavior in open savannas of the Cerrado

Understanding how future climate periods influence fire behaviour is important for organizing fire suppression strategy and management . The meteorological factors are the most critical parameters affecting fire behaviour in natural landscapes; hence, predicting climate change effects on fire behaviour could be an option for optimizing firefighting resource management. In this study, we assessed climate change impacts on fire behaviour parameters (rate of fire growth, rate of spread and fireline intensity) for a typical Mediterranean landscape of Greece. We applied the minimum travel time fire simulation algorithm by using the FlamMap software to characterize potential response of fire behaviour for three summer periods. The results consisted of simulated spatially explicit fire behaviour parameters of the present climate (2000) and three future summer periods of 2050, 2070 and 2100, under the A1B emissions scenario. Statistical significant differences in simulation outputs among the four examined periods were obtained by using the Tukey’s significance test. Statistical significant differences were mainly obtained for 2100 compared to the present climate due to the significant projected increase in the wind speed by the end of the century. The analysis and the conclusions of the study can be important inputs for fire suppression strategy and fire management (deployment of fire suppression resources, firefighter safety and exposure, transportation logistics) quantifying the effect that the expected future climate periods can have on fire suppression difficulty in Mediterranean landscapes.

Experimental manipulation of fuel structure to evaluate the potential ecological effects of fire

Managing fires in a changing world: Fuel and weather determine fire behavior and safety in the neotropical savannas

Accurate prediction of bushfire behaviour is essential for effective fire management. Such knowledge allows for the timely determination of the potential threat and impacts of a fire and provides the basis for sound fire-management decision-making. Fire behaviour prediction combines quantitative and qualitative information sources that are based on scientific principles and personal experience describing the combustion and behaviour of fire in a range of weather, fuel and topographic conditions. 'Amicus', the National Fire Behaviour Knowledge Base, is a new software-based tool under development that endeavours to provide a unique framework in which each of these information sources is accessible and utilisable in a consistent and comprehensive manner for the sole purpose of operational prediction of the behaviour of bushfires by trained fire behaviour analysts. The Amicus system comprises four primary components: fuel description, fuel moisture models, wind models and fire behaviour models and uses these to predict fire characteristics (e.g. rate of spread, flame height, fireline intensity, onset of crowning, spotting potential) for a broad range of burning conditions. This paper details the current development of the fire behaviour component of Amicus and its proposed integration with the Australian Bushfire Fuel Classification System being developed for use across all Australian jurisdictions. The fire behaviour component will integrate a suite of fire behaviour models covering the main Australian fuel types: eucalyptus forests, exotic pine plantations, grasslands and shrublands. Further development of Amicus will integrate the fire weather, fuel dynamics, and suppression capability knowledge and science to help fire managers better predict bushfire behaviour and better plan prescribed burns.

Developing custom fire behavior fuel models from ecologically complex fuel structures for upper Atlantic Coastal Plain forests

Some invasive grasses have been reported to change fire behavior in invaded plant communities. Urochloa brizantha is an aggressive invasive grass in the Brazilian Cerrado, an ecosystem where fire is a common disturbance. We investigated the effects of U. brizantha on fire behavior in an open Cerrado physiognomy in Central Brazil. Using experimental burnings we compared fire behavior at both the community and the individual plant level in invaded (UJ) and non-invaded (NJ) areas burned in July. We also assessed the effect of fire season in invaded areas by comparing July (UJ) and October (UO) burnings. We evaluated the following variables: fuel load, fuel moisture, combustion efficiency, maximum fire temperature, flame height, and fire intensity. Additionally, we evaluated the temperatures reached under invasive and native grass tussocks in both seasons. Fuel load, combustion efficiency, and fire intensity were higher in NJ than in UJ, whilst flame height showed the opposite trend. Fuel amount and fire intensity were higher in October than in July. At the individual plant level, U. brizantha moisture was higher than that of native species, however, temperatures reaching ≥600 °C at ground level were more frequent under U. brizantha tussocks than under native grasses. At the community level, the invasive grass modified fire behavior towards lower intensity, lower burning efficiency, and higher flame height. These results provide essential information for the planning of prescribed burnings in invaded Cerrado areas.

Because of its high frequency and generally low intensity, fire in tropical savannas appears to be a different phenomenon from that in other biomes. A recent study of fire in savanna at Munmarlary in northern Australia, analysed by detrended correspondence analysis (DCA) concluded that different fire regimens resulted in negligible changes in the vegetation, a conclusion crucial for fire management in the region.Here, we describe the short‐term impact of an unusually intense fire in an area of tropical open forest. Tree and shrub mortality of 14.3% was recorded within 6 months of the fire, and the composition of the vegetation was changed because of differences between species in mortality rates, which ranged from 4 to 90%. Analyses of variance (ANOVA) of DCA co‐ordinates were unable to detect any change, however. DCA seems inappropriate for analysing vegetation changes after savanna fires, because the floristic changes, compared with those in temperate fire‐prone ecosystems, are subtle and multidirectional.Further, it is shown that rather large plot sizes (2–4 ha) are likely to be required to detect fire treatment differences even as great as about 20% of the mean, given the variability of savanna vegetation, and replicates that are likely to be limited in number. A possible solution is to measure the change over time in permanent plots, rather than attempting to detect treatment differences by sampling on a single occasion.

Fire management business in Australia's tropical savannas: Lighting the way for a new ecosystem services model for the north?

When developing a research roadmap for human behaviour in fires, it is necessary to identify areas that require additional research. A general overview – from a multidisciplinary perspective – of gaps in human behaviour in fires research across multiple contexts is missing. The goal of this paper was to perform a scoping review to identify research gaps and themes in all aspects of human behaviour in fires across contexts. This scoping review included 17 articles. In total, 37 research gaps and 11 research themes for the built environment and community context were identified. The main research gaps are related to cognitive factors, behavioural responses, environmental factors and physical/physiological factors. Also, for all research themes, additional research involving heterogenous populations is required. Furthermore, there is an imbalance in human behaviour in fires studies: most articles were focused on the built environment rather than the community context. Finally, the topic of intoxication has received limited research attention, and data collection methods lack diversity. Future research should not only be done from a multidisciplinary perspective but also interdisciplinary research efforts are required. The availability of more data and knowledge on human behaviour and responses in fires could be beneficial to simulation model developers/users, the general public and fire safety managers.

Aim This study aimed to quantify changes in fire severity resulting from the invasion of Australia’s tropical savannas by the African grass Andropogon gayanus Kunth. (gamba grass).Location Mesic savannas of the Northern Territory, Australia.Method Byram’s fire‐line intensity (If), fuel load and architecture, and two post‐fire indicators of fire intensity – scorch height (SH) and char height (CH) of woody vegetation – were determined for fires in native grass savanna and A. gayanus invaded savanna. Leaf scorch is the height at which the fire’s radiant heat browns leaf tissue, and leaf char is the height that radiant heat blackens or consumes leaf tissue and provides an indirect measure of flame height. These data, and 5 years of similar data collected from the Kapalga Fire Project in Kakadu National Park, were used to develop empirical relationships between If and the post‐fire indices of fire intensity.Results A relationship between A. gayanus If and SH could not be developed because complete canopy scorch occurred in most A. gayanus fires, even at low If. In contrast, A. gayanus If was strongly correlated with CH. This empirical relationship was substantially different from that for native grass fires. For a given If, there was a significantly greater CH in invaded sites. This increase in radiant heat is attributable to the increased biomass (mean 3.6 t ha−1 in native grasses compared to 11.6 t ha−1 in A. gayanus) and height (approximately 0.5 m in native grasses compared to 4 m in A. gayanus) of the standing fine fuel.Main conclusion Andropogon gayanus invasion resulted in substantial changes in fire behaviour. This has important regional implications owing to the current (10,000–15,000 km2) and predicted (380,000 km2) area of invasion and the negative consequences for the native savanna biota that has evolved with frequent but relatively low‐intensity fire.

BackgroundPrescribed 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.ResultsFireline 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.ConclusionsFire 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.

Fire drives evolutionary and ecological process in tropical savannas. Nevertheless, fire as a tool for managing biodiversity in wildlands is still controversial and encounters strong resistances. For decades, fire in savanna's protected areas was perceived as ‘an evil' requiring strong efforts for its suppression. Anti-fire policy had led to large and recurrent wildfire due to fuel load accumulation and vegetation continuity, also impacting traditional livelihood in savannas. Circumstantially, fire use and management has been accepted as a ‘necessary evil' in order to avoid wildfires. An emerging fire management policy has been recognizing fire as ‘a necessity' for savannas' biodiversity and people, dealing with intercultural governances. Such a participatory fire management approach is in the context of Integrated Fire Management (IFM). In Brazil, a paradigm shift in fire policies is underway, and the telling of such institutional change must consider the experience of Serra Geral do Tocantins Ecological Station. This is a strict protected area (PA) of 7000km², created in 2001 by a federal act. After a decade of anti-fire management policy, the PA was annually dealing with large and destructive wildfire, with strong impact also on traditional burning systems. The negotiation of a fire management agreement with local traditional people, who recognize themselves as quilombolas, involved discussions, meetings and training, led to a progressive paradigm change - first accepting the controlled use of fire and currently integrating multiple perspectives on burning, aiming to create a patch mosaic burning for biodiversity conservation. Besides reduction of large wildfires occurrences, there is a healthy environment of collective learning and reduced conflict. Such management changes are fully incorporated into management instruments, representing positive impacts at the institutional level through debates and conceptual developments, and the learning are being shared with other PAs and at national and international levels.

BackgroundFire is important for the maintenance of African savanna ecosystems, particularly humid savanna. Despite the importance of fire behavior to our understanding of fire’s ecological effects, few studies have documented fire behavior and its determinants in humid West African savannas and, in particular, whether fire behavior depends on season of the year. We analyzed fire behavior in the Guinean savanna of Lamto (Ivory Coast) during a 4-year field experiment. The fire regimes tested consisted of three different burning seasons: early-season fire, mid-season fire, and late-season fire. Nine 0.5 ha plots were burned annually to determine the rate of spread and fire intensity. Fuel characteristics and weather conditions were measured to assess their impact on fire behavior.ResultsUnderstory grass height, total fresh fuel load, and moisture content had greater values in early-season fire than in mid-season and late-season fire. The rate of spread and intensity of both mid-season fire (0.14 ± 0.03 m s−1 and 3920 ± 740 kW m−1, respectively) and of late-season fire (0.12 ± 0.02 m s−1 and 3134 ± 482 kW m−1, respectively) were significantly greater than those of early-season fire (0.04 ± 0.01 m s−1 and 1416 ± 252 kW m−1, respectively). The best predictors of fire behavior were fuel moisture content and air humidity; these two explanatory variables were the sole significant predictors for fire intensity, rate of fire spread, and flame height.ConclusionsGiven that there is no difference between intensity of mid-season and late-season fire, we suggest that the generally reported higher impact of late-season fire on trees in the West African humid savannas is due not to fire intensity per se, but rather to a more sensitive phenological stage of trees (e.g., leafless in mid-season), and to a longer time of exposure to lethal temperatures (> 60 °C) in the late dry season. These data provide important insights into fire behavior in the Guinean savanna−forest mosaic ecoregion, informing fire management.

Fire management implications of fuel loads and vegetation structure in jarrah forest restoration on bauxite mines in Western Australia