المؤلفون: Andres F. Osorio, Mohamad L. Ramadhan, Jeronimo Carrascal, Juan P. Hidalgo

المصدر: International Journal of Wildland Fire. 30:680-690

مصطلحات موضوعية: 040101 forestry, Eucalyptus saligna, Curing (food preservation), Ecology, biology, Moisture, Forestry, 04 agricultural and veterinary sciences, biology.organism_classification, law.invention, Ignition system, Heat flux, law, Range (aeronautics), 0401 agriculture, forestry, and fisheries, Environmental science, Physics::Chemical Physics, Composite material, Water content, Physics::Atmospheric and Oceanic Physics, Flammability

الوصف: Fuel moisture content is one of the key parameters controlling the flaming ignition of wildland fuel. However, the role of fuel moisture content in assessing the flammability of different fuel curing (dead and live fuel) is still not well understood. This paper presents the results of ignition tests of fuel beds consisting of dead and live Eucalyptus saligna leaves under a wide range of moisture contents. External heat flux and fuel moisture content are shown to significantly influence time to ignition and mass loss rate at the ignition of Eucalyptus saligna leaves, thus illustrating distinctive heating processes in the fuel bed. The thermal behaviour of the leaf bed before ignition is analysed using the analytical solution to the heat conduction equation, as the classical ignition correlations yield inconclusive results. This approach allows identification of thermally thick and thin behaviours for distinct ranges of heating, with the transition (thermally intermediate) region observed at higher external heat fluxes for higher moisture content. Additionally, a flammability assessment based on time to ignition confirms the inadequacy of the common assumption that live fuel can be considered as moist dead fuel.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::a87da7d40a743eb3c9fdadd674688528Test
https://doi.org/10.1071/wf20069Test

المؤلفون: Yu Hongzhou, Lifu Shu, Deng Jifeng, Guang Yang

المصدر: International Journal of Wildland Fire. 30:462-466

مصطلحات موضوعية: 040101 forestry, 010504 meteorology & atmospheric sciences, Ecology, Moisture, biology, Extrapolation, Forestry, 04 agricultural and veterinary sciences, biology.organism_classification, Atmospheric sciences, 01 natural sciences, Equilibrium moisture content, Twig, Degree (temperature), Approximation error, 0401 agriculture, forestry, and fisheries, Environmental science, Larch, Water content, 0105 earth and related environmental sciences

الوصف: The Daxinganling Region, in Heilongjiang Province, China, has experienced considerable losses to forest resources owing to a recent increase in forest fire frequency. This necessitates the predictions of fire behaviour in this region, which requires assessment of fuel moisture content (FMC) at appropriate space and time intervals. Here, we compare and extrapolate results of vapour-exchange methods for predicting hourly moisture contents of downed wood. The FMC of larch and birch twig fuels was measured at 1-h intervals at different slope positions with respect to meteorological factors. The twigs were categorised based on diameter and degree of decay. The Nelson and Simard methods (which consider equilibrium moisture content and the associated time lag) and direct regression method (which allows direct attainment of the FMC) were used. Both Nelson and Simard methods predicted hourly twig moisture content more accurately than the direct regression method. The Simard method was the most accurate, with the lowest mean absolute error and mean relative error as well as relatively small variation coefficients based on results of the extrapolation analysis. Further, the resulting models applied to needle-leaved and lightly decomposed fuels performed better than for the broad-leaved and badly decomposed fuels on evaluation parameters.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::a41b1d0124b1085d6958fe5cabd10f1cTest
https://doi.org/10.1071/wf19184Test

المؤلفون: Yanhui Liu, Xinyan Huang, Shaorun Lin

المصدر: International Journal of Wildland Fire. 30:454-461

مصطلحات موضوعية: 040101 forestry, Hydrology, Smouldering, Peat, 010504 meteorology & atmospheric sciences, Ecology, Water flow, Water table, Forestry, 04 agricultural and veterinary sciences, 01 natural sciences, Disturbance (ecology), Greenhouse gas, 0401 agriculture, forestry, and fisheries, Environmental science, Firebreak, Water content, 0105 earth and related environmental sciences

الوصف: Smouldering wildfire is an important disturbance to peatlands worldwide; it contributes significantly to global carbon emissions and provides positive feedback to climate change. Herein, we explore the feasibility of firebreaks to control smouldering peat fires through laboratory-scale experiments. The dry-mass moisture content (MC) of peat soil was varied from 10% (air-dried) to 125%. We found that smouldering peat fire may be successfully extinguished above the mineral soil layer, even if the peat layer is not entirely removed. There are two criteria for an effective peat firebreak: (I) adding water to make the peat layer sufficiently wet (>115% MC in the present work); and (II) ensuring that the peat layer is thinner than the quenching thickness (< 5 cm). Criterion I may fail if the water table declines or the peat layer is dried by surface fires and hot weather; thus, satisfying Criterion II is more attainable. A sloping trench-shaped firebreak is recommended to guide water flow and help maintain high peat moisture content. This work provides a scientific foundation for fighting and mitigating smouldering wildfires and provides guidance about protective measures for field-scale peat fire experiments.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::dcdf4f880b4af3ee884c37b4fdc9436bTest
https://doi.org/10.1071/wf20155Test

المؤلفون: Helen Y. Smith, Pamela G. Sikkink, Lisa M. Holsinger, Robert E. Keane

المصدر: International Journal of Wildland Fire. 29:57

مصطلحات موضوعية: 040101 forestry, 0106 biological sciences, Hydrology, Ecology, Moisture, Wire mesh, Prescribed burn, Forestry, 04 agricultural and veterinary sciences, 010603 evolutionary biology, 01 natural sciences, 0401 agriculture, forestry, and fisheries, Environmental science, Fuel treatment, Mastication, Water content

الوصف: Mastication is becoming a popular wildland fuel treatment in the United States but little is known about how masticated fuels dry over time, especially as these atypical fuelbeds age. This report summarises measured drying rates of different-aged masticated fuelbeds built from material collected from sites that were treated using one of four mastication techniques. We recreated three replicates of masticated fuelbeds in wire mesh cages using material collected from 13 sites sampled throughout the US Rocky Mountains. These caged fuelbeds were saturated and then their moisture contents were measured daily as they dried over 10 days in both a controlled growth chamber and outdoors. Relative moisture content after 24 and 96h of drying and a drying rate were response variables that were analysed across fuel age, drying environment and mastication method. While our sites occurred across different forest types and climates and the mastication equipment used was different, we found that all fuelbeds dried within 3% of the equilibrium moisture contents (3–6%) after ~96h for both growth chamber and outdoors under moderately dry environments. We also found that mastication method influenced fuelbed drying rates whereas age had little effect. Fire managers may use these drying rates to implement effective prescribed burns to reduce adverse impacts when masticated fuelbeds burn during wildfire conditions.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::840ddb72aa9b72645962629201c679e8Test
https://doi.org/10.1071/wf19021Test

المؤلفون: David L. Blunck, Daniel A. Cowan, Bret W. Butler, Wesley G. Page

المصدر: International Journal of Wildland Fire. 29:820

مصطلحات موضوعية: 040101 forestry, Smouldering, Peat, Ecology, Moisture, Forestry, Soil science, 04 agricultural and veterinary sciences, Spread rate, 01 natural sciences, Bulk density, 010406 physical chemistry, 0104 chemical sciences, Pinus , chemistry.chemical_compound, chemistry, 0401 agriculture, forestry, and fisheries, Environmental science, Cellulose, Water content

الوصف: The slow-moving flameless burning of wildland fuels (i.e. smouldering) can be difficult to detect and challenging to extinguish. Although previous research involving the smouldering of organic fuels (e.g. cotton, cellulose, peat) has investigated the influence of various fuel characteristics (e.g. moisture content, inorganic content, bulk density) on spread rate and surface temperatures, the smouldering behaviour of other common fuels is not well understood. This study expands on previous research to better understand how fuel characteristics influence the smouldering behaviour of duff from coniferous forests. Specifically, horizontal spread rates (0.5–19.5cm h−1) and ground surface temperatures (258–392°C) were measured on 52 duff samples collected from underneath mature ponderosa pine trees (Pinus ponderosa) from sites in the Pacific Northwest, USA, and evaluated in terms of their moisture content (6–113%), inorganic content (3–42%), bulk density (34–130kgm−3) and fuel depth (3.8–16.3cm). The data suggested that horizontal spread rates decrease when inorganic content, inorganic loading and/or moisture loading of the duff increases. Surface temperatures decrease when inorganic bulk density and/or fuel loading increases. Conversely, surface temperatures decrease when moisture content increases for shallow duff. Higher fuel loading increases the likelihood of smouldering below the surface.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::9e024d29d597548fbe6f201bbc622f3cTest
https://doi.org/10.1071/wf19207Test

المؤلفون: Kelsy Gibos, Thomas J. Duff, William D. Bovill, Annette Menzel, Christian Schunk, Gary Sheridan, Petter Nyman, Jane G. Cawson, Gianni Boris Pezzatti, Marco Conedera

المصدر: International Journal of Wildland Fire. 29:548

مصطلحات موضوعية: 040101 forestry, Hydrology, 010504 meteorology & atmospheric sciences, Ecology, Moisture, Microclimate, Fuel moisture content, Forestry, Context (language use), 04 agricultural and veterinary sciences, 01 natural sciences, Linear relationship, Range (aeronautics), Calibration, 0401 agriculture, forestry, and fisheries, Environmental science, Water content, 0105 earth and related environmental sciences

الوصف: Field measurements of surface dead fine fuel moisture content (FFMC) are integral to wildfire management, but conventional measurement techniques are limited. Automated fuel sticks offer a potential solution, providing a standardised, continuous and real-time measure of fuel moisture. As such, they are used as an analogue for surface dead fine fuel but their performance in this context has not been widely evaluated. We assessed the ability of automated fuel sticks to predict surface dead FFMC across a range of forest types. We combined concurrent moisture measurements of the fuel stick and surface dead fine fuel from 27 sites (570 samples), representing nine broad forest fuel categories. We found a moderate linear relationship between surface dead FFMC and fuel stick moisture for all data combined (R2=0.54), with fuel stick moisture averaging 3-fold lower than surface dead FFMC. Relationships were typically stronger for individual forest fuel categories (median R2=0.70; range=0.55–0.87), suggesting the sticks require fuel-specific calibration for use as an analogue of surface dead fine fuel. Future research could identify fuel properties that will enable more generalised calibration functions.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::971e079ca43b8b9e30a86058b67f2de3Test
https://doi.org/10.1071/wf19061Test

المؤلفون: Grant J. Williamson, David M. J. S. Bowman, Ben J. French, Kathryn Storey, Lynda D. Prior

المصدر: International Journal of Wildland Fire. 29:637

مصطلحات موضوعية: 040101 forestry, Smouldering, Hydrology, 010504 meteorology & atmospheric sciences, Ecology, Moisture, Soil organic matter, Forestry, 04 agricultural and veterinary sciences, Soil carbon, Vegetation, 01 natural sciences, Bulk density, Soil water, 0401 agriculture, forestry, and fisheries, Environmental science, Water content, 0105 earth and related environmental sciences

الوصف: The present study aimed to determine moisture thresholds for combustion of organic soils sampled from various vegetation types at 63 locations in Tasmania, Australia. To observe whether the soil sample sustained smouldering combustion, moisture content was experimentally manipulated and heat was applied. Combustion was primarily determined by moisture content, but was also influenced by soil bulk density and organic content: the gravimetric moisture content corresponding to a 50% probability of burning ranged from 25 to 94% as organic content varied from 34 to 96%. There was no evidence of differences among vegetation types in the relationship between soil combustibility and organic content. Combustion in Tasmanian organic soils occurred with moisture levels similar to those reported elsewhere, despite differences in vegetation and environment. It was also found that a hand-held meter that measured volumetric moisture content using time domain reflectometry could be used to satisfactorily predict organic soil combustion. Finally, combining the data with estimates of volumetric soil moisture based on high-resolution gridded weather data (Bureau of Meteorology Atmospheric high-resolution Regional Reanalysis for Australia, or BARRA), it was demonstrated that most Tasmanian organic soils are likely to be combustible at some time almost every summer (December to February).

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::fa5af9fa055ed9328bb64b574a499c34Test
https://doi.org/10.1071/wf19196Test

المؤلفون: Evan Ellicott, Nathaniel May, Michael J. Gollner

المصدر: International Journal of Wildland Fire. 28:187

مصطلحات موضوعية: 040101 forestry, Ecology, Moisture, Air pollution, Biomass, Forestry, 04 agricultural and veterinary sciences, Particulates, Combustion, Atmospheric sciences, medicine.disease_cause, chemistry.chemical_compound, chemistry, Carbon dioxide, medicine, Fuel efficiency, 0401 agriculture, forestry, and fisheries, Environmental science, Water content

الوصف: A series of small-scale laboratory fires were conducted to study the relationship between fuel type, moisture content, energy released and emissions during the combustion process of live wildland fuels. The experimental design sought to understand the effects that varying moisture content of different fire-promoting plant species had on the release of total energy, gaseous emissions (CO, CO2), particulate matter less than 2.5µm in diameter (PM2.5) and fire radiative energy (FRE). Instantaneous FRE, or fire radiative power (FRP), is an important parameter used in remote sensing to relate the emitted energy to the biomass fuel consumption. Currently, remote sensing techniques rely on empirically based linear relationships between emitted FRE and biomass consumed. However, this relationship is based on the assumption that all fuels emit the same amount of energy per unit mass, regardless of fuel conditions (type, moisture, packing, orientation, etc.). In this study, we revisited these assumptions under the influence of moisture content for species that are adapted to fire, containing volatile oils. Results show that, in terms of the total energy released, this assumption holds fairly well regardless of fuel type and moisture content. However, FRE was found to be slightly dependent on the fuel type and very dependent on the moisture content of the fuel. Most of this variation was attributed to changes in the behaviour of the combustion process for different fuels, similarly observed in emissions measurements. These results highlight a need to further examine the role of fuel moisture and combustion state when determining emissions from remotely sensed measurements.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::b92db9f7c76091f7de6a7b533c530393Test
https://doi.org/10.1071/wf18084Test

المؤلفون: Jili Zhang, Rui Wei, Wang Xiaohong, Guang Yang, Xin Zhou

المصدر: International Journal of Wildland Fire. 28:969

مصطلحات موضوعية: 040101 forestry, Ecology, biology, business.industry, Forestry, Soil science, 04 agricultural and veterinary sciences, biology.organism_classification, Temperature measurement, Mongolian oak, Thermal insulation, visual_art, Heat transfer, visual_art.visual_art_medium, 0401 agriculture, forestry, and fisheries, Surface structure, Environmental science, Bark, Cambium, business, Water content

الوصف: The survival probability of a tree exposed to surface fire varies widely depending on its bark. To advance the understanding of insulation properties of bark, mean thickness (BT), moisture content (MCb), surface structure (BS) and density (ρb) of bark samples of Mongolian oak (Quercus mongolica) (n=395) for four diameter classes were investigated. In addition, data from 158 heating experiments simulating low-intensity surface fires in the laboratory were used to assess the relative importance of these properties affecting thermal insulation and evaluate the applicability of two stem heating models, an analytical, one-dimensional model and the FireStem2D model. Overall, BT is the best predictor of bark insulation capacity and MCb only contributes significantly to explain the residence time of cambial temperature >60°C (τ>60), whereas ρb and BS have minor effects. Although the two stem heating models overestimate the time required for cambium temperatures to reach 60°C (τ60), FireStem2D performed better than analytical model. Furthermore, FireStem2D provides good predictions of τ>60 and maximal cambial temperature (Tmax). In addition, errors in FireStem2D may be driven mainly by the errors in temperature measurement and the limitation of a two-dimensional model. The study provides a better knowledge of interactions between bark properties and heat transfer, which may improve the predictability of fire-caused stem injury for Mongolian oak and other species with similar bark properties.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::c42e2695d0a4b0f43b0f58e68f9eb32eTest
https://doi.org/10.1071/wf18232Test

المؤلفون: Yves Bergeron, Jeanne Portier, Sylvie Gauthier

المصدر: International Journal of Wildland Fire. 28:927

مصطلحات موضوعية: 040101 forestry, Ecology, Fire regime, Taiga, Climate change, Poison control, Forestry, 04 agricultural and veterinary sciences, Spatial distribution, Lightning strike, 0401 agriculture, forestry, and fisheries, Environmental science, Spatial variability, Physical geography, Water content

الوصف: In Canada, recent catastrophic wildfire events raised concern from governments and communities. As climate change is expected to increase fire activity in boreal forests, the need for a better understanding of fire regimes is becoming urgent. This study addresses the 1972–2015 spatial distributions of fire cycles, mean fire size (FireSz) and mean fire occurrence (mean annual number of fires per 100000ha, FireOcc) in eastern Canada. The objectives were to determine (1) the spatial variability of fire-regime attributes, (2) the capacity of FireSz and FireOcc to distinguish homogeneous fire zones and (3) the environmental factors driving FireSz and FireOcc, with some emphasis on lightning strikes. Fire cycles, FireSz and FireOcc greatly varied throughout the study area. Even within homogeneous fire zones, FireSz and FireOcc were highly variable. FireSz was controlled by moisture content in deep layers of the soil and by surficial deposits, whereas FireOcc was controlled by moisture content in top layers of the soil and by relief. The lack of a relationship between FireOcc and lightning-strike density suggested that the limiting effect of lightning-strike density on FireOcc could be operating only under certain circumstances, when interacting with other environmental factors.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::35778bd64d73e279d0ae7d9a69e6995aTest
https://doi.org/10.1071/wf18220Test