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1.
Estimation of canopy fuel characteristics of Aleppo pine (Pinus halepensis Mill.) forests in Greece based on common stand parameters 总被引：1，自引：0，他引：1
Canopy fuel characteristics that influence the initiation and spread of crown fires were measured in forty representative Aleppo pine (Pinus halepensis Mill.) stands in Greece. Aleppo pine canopy fuels are characterized by low canopy base height (CBH) (2.0–6.5 m), while available canopy fuel load (CFL) (0.63–1.82 kg/m2) and canopy bulk density (CBD) (0.07–0.22 kg/m3) values are similar to those of other conifers worldwide. Regression equations for the estimation of canopy fuels were developed based on common stand parameters. Stand basal area was the best-fitted predictor for the estimation of CFL and CBD at stand level, explaining 77 and 74 % of the observed variation, respectively. Regression analysis failed to provide any significant estimates for the CBH. Prediction of canopy fuel characteristics based on stand basal area can be useful in fuel management and fire prevention planning since it and can be easily incorporated into existing forest inventory systems and can be used for the Kyoto protocol requirements of carbon changes in Aleppo pine forests located in Greek sites. 相似文献
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Canopy fuel characteristics in relation to crown fire potential in pine stands: analysis, modelling and classification 总被引：1，自引：0，他引：1
José María Fernández-Alonso Iciar Alberdi Juan Gabriel Álvarez-González José Antonio Vega Isabel Cañellas Ana Daría Ruiz-González 《European Journal of Forest Research》2013,132(2):363-377
Crown fire occurrence and subsequent crown fire behaviour are strongly dependent on canopy fuel characteristics, especially canopy fuel load (CFL), canopy bulk density (CBD) and canopy base height (CBH). Therefore, quantification of such variables is required for the appropriate selection of silvicultural treatments aimed at reducing susceptibility to crown fire. Data from the IV Spanish National Forest Inventory and individual tree biomass dry weight equations were used to estimate the canopy fuel characteristics of four representative types of pine stands in north-western Spain. Probability of crown fire initiation and crown fire rate of spread were simulated by using the mean surface fuel load observed for each type of pine in this area and assuming different burning conditions. The results indicate that a 22.13 % of the sample plots analysed showed a rather high potential for active crown fire spread under moderate burning conditions, and this value increases to 69.27 % under extreme burning conditions. Equations relating the canopy fuel characteristics to common stand variables (stand density, basal area and dominant height) were fitted simultaneously for each pine, and weighting factors for heteroscedasticity were included. The models explained more than 93.90, 74.70 and 69.42 % of the observed variability in CFL, CBD and CBH, respectively. Basal area was the most important variable for estimating CFL and CBD while dominant height explained most of the observed variability in CBH. The use of the fitted equations together with existing dynamic growth models and fire management decision support systems will enable assessment of the crown fire potential associated with different silvicultural alternatives used in these types of pine stands. 相似文献
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A. P. Dimitrakopoulos I. D. Mitsopoulos D. I. Raptis 《European Journal of Forest Research》2007,126(4):555-561
Nomographs that calculate the threshold values of surface fire parameters which lead to crown fire initiation were created
by linking two separate fire behavior models: Van Wagner’s crown fire ignition criteria and Byram’s surface fire model. The
nomographs were also based on the existing surface (fuel load, fuel heat content) and canopy (foliar moisture content, live
crown base height) fuel models of Aleppo (Pinus halepensis Mill.) pine forests of Mediterranean Greece. The most important fire parameters for crown fire initiation that are calculated
by the nomographs are the critical flame length and the forward spread rate of the surface fire. These parameters are readily
observable in the field during fires. The nomographs provide a judicious way to assess whether a crown fire is likely to occur
in a conifer forest stand. Although the fire behavior models used had limited testing and are based on certain assumptions,
yet they are widely applied in forestry practice worldwide, as a basis for justified fire prevention and suppression planning. 相似文献
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Alicia L. Reiner Nicole M. Vaillant JoAnn Fites-Kaufman Scott N. Dailey 《Forest Ecology and Management》2009,258(11):2365-2372
Due to increases in tree density and hazardous fuel loading in Sierra Nevadan forests, land management is focusing on fuel reduction treatments to moderate the risk of catastrophic fires. Fuel treatments involving mechanical and prescribed fire methods can reduce surface as well as canopy fuel loads. Mastication is a mechanical method which shreds smaller trees and brush onto the surface fuel layer. Little data exist quantifying masticated fuel beds. Despite the paucity of data on masticated fuels, land managers desire fuel loading, potential fire behavior and fire effects such as tree mortality information for masticated areas. In this study we measured fuel characteristics before and after mastication and mastication plus prescribed burn treatments in a 25-year old ponderosa pine (Pinus ponderosa C. Lawson) plantation. In addition to surface fuel characteristics and tree data collection, bulk density samples were gathered for masticated material. Regressions were created predicting masticated fuel loading from masticated fuel bed depth. Total masticated fuel load prior to fire treatment ranged from 25.9 to 42.9 Mg ha−1, and the bulk density of masticated fuel was 125 kg m−3. Mastication treatment alone showed increases in most surface fuel loadings and decreases in canopy fuel loads. Masticated treatment in conjunction with prescribed burning reduced both surface and canopy fuel loads. Detailed information on fuel structure in masticated areas will allow for better predictions of fire behavior and fire effects for fire in masticated fuel types. Understanding potential fire behavior and fire effects associated with masticated fuels will allow managers to make decisions on the possibility of mastication to create fuel breaks or enhance forest health. 相似文献
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Michael J. Jenkins Elizabeth Hebertson Wesley Page C. Arik Jorgensen 《Forest Ecology and Management》2008
Bark beetle-caused tree mortality in conifer forests affects the quantity and quality of forest fuels and has long been assumed to increase fire hazard and potential fire behavior. In reality, bark beetles, and their effects on fuel accumulation, and subsequent fire hazard, are poorly understood. We extensively sampled fuels in three bark beetle-affected Intermountain conifer forests and compared these data to existing research on bark beetle/fuels/fire interactions within the context of the disturbance regime. Data were collected in endemic, epidemic and post-epidemic stands of Douglas-fir, lodgepole pine and Engelmann spruce. From these data, we evaluated the influence of bark beetle-caused tree mortality on various fuels characteristics over the course of a bark beetle rotation. The data showed that changes in fuels over time create periods where the potential for high intensity and/or severe fires increases or decreases. The net result of bark beetle epidemics was a substantial change in species composition and a highly altered fuels complex. Early in epidemics there is a net increase in the amount of fine surface fuels when compared to endemic stands. In post-epidemic stands large, dead, woody fuels, and live surface fuels dominate. We then discuss potential fire behavior in bark beetle-affected conifer fuels based on actual and simulated fuels data. Results indicated that for surface fires both rates of fire spread and fireline intensities were higher in the current epidemic stands than in the endemic stands. Rates of spread and fireline intensities were higher in epidemic stands due, however, to decreased vegetative sheltering and its effect on mid-flame wind speed, rather than changes in fuels. Passive crown fires were more likely in post-epidemic stands, but active crown fires were less likely due to decreased aerial fuel continuity. We also discuss the ecological effects of extreme fire behavior. Information is presented on managing forests to reduce the impact of bark beetle outbreaks and the interplay between management, bark beetle populations, fuels and fire hazard and behavior. 相似文献
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A key challenge in modern wildfire mitigation and forest management is accurate mapping of forest fuels in order to determine spatial fire hazard, plan mitigation efforts, and manage active fires. This study quantified forest fuels of the montane zone of Boulder County, CO, USA in an effort to aid wildfire mitigation planning and provide a metric by which LANDFIRE national fuel maps may be compared. Using data from 196 randomly stratified field plots, pre-existing vegetation maps, and derived variables, predictive classification and regression tree models were created for four fuel parameters necessary for spatial fire simulation with FARSITE (surface fuel model, canopy bulk density, canopy base height, and stand height). These predictive models accounted for 56–62% of the variability in forest fuels and produced fuel maps that predicted 91.4% and 88.2% of the burned area of two historic fires simulated in the FARSITE model. Simulations of areas burned based on LANDFIRE national fuel maps were less accurate, burning 77.7% and 40.3% of the historic fire areas. Our results indicate that fuel mapping efforts that utilize local area information and biotic as well as abiotic predictors will more accurately simulate fire spread rates and reflect the inherent variability of forested environments than do current LANDFIRE data products. 相似文献
10.
Effects of vegetation type and fire regime on flammability of undisturbed litter in Southeastern France 总被引：1，自引：0，他引：1
Anne Ganteaume Jappiot MarielleLampin-Maillet Corinne Curt ThomasBorgniet Laurent 《Forest Ecology and Management》2011,261(12):2223-2231
To assess the effect of vegetation types and of fire regime on the flammability of dead fuels, samples of litter were collected undisturbed (i.e. keeping the structure of litter layers) in 29 study sites spread over the limestone-derived soils of Provence. The sampling plan comprised the most representative ecosystems of the study area: pure Pinus halepensis stands, mixed pine-oak stands and shrublands. Three classes of litter depth were studied (low, medium and high) to account for the variability existing in the field. Sampling also included the number of fires in each site since 1960 (no fire, 1 or 2 fires and ≥3 fires) and the time interval since the last fire (≤15 years, 15-45 years and >45 years). Flammability experiments were carried out in laboratory using a glowing firebrand and a 10 km h−1 wind. The main variables recorded were: ignition frequency, time-to-ignition, flaming duration, flame rate of spread, flame propagation, mean flame temperature, maximum flame height and rate of consumption.Results showed that the ignition frequency was higher in mixed stands than in pure pine stands whereas the time-to ignition, flaming duration and rate of consumption were the highest in pure pine stands. The maximum flame height and the flame propagation decreased with the increase of the number of fires and the time-to-ignition was the highest when the interval since the last fire was the shortest. Increases in litter depth resulted in increased mean flame temperature, maximum flame height and flame propagation. These results can be explained, in part, by the proportions of the different litter components. 相似文献
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Fire plays an important role in shaping many Sierran coniferous forests, but longer fire return intervals and reductions in area burned have altered forest conditions. Productive, mesic riparian forests can accumulate high stem densities and fuel loads, making them susceptible to high-severity fire. Fuels treatments applied to upland forests, however, are often excluded from riparian areas due to concerns about degrading streamside and aquatic habitat and water quality. Objectives of this study were to compare stand structure, fuel loads, and potential fire behavior between adjacent riparian and upland forests under current and reconstructed active-fire regime conditions. Current fuel loads, tree diameters, heights, and height to live crown were measured in 36 paired riparian and upland plots. Historic estimates of these metrics were reconstructed using equations derived from fuel accumulation rates, current tree data, and increment cores. Fire behavior variables were modeled using Forest Vegetation Simulator Fire/Fuels Extension.Riparian forests were significantly more fire prone under current than reconstructed conditions, with greater basal area (BA) (means are 87 vs. 29 m2/ha), stand density (635 vs. 208 stems/ha), snag volume (37 vs. 2 m3/ha), duff loads (69 vs. 3 Mg/ha), total fuel loads (93 vs. 28 Mg/ha), canopy bulk density (CBD) (0.12 vs. 0.04 kg/m3), surface flame length (0.6 vs. 0.4 m), crown flame length (0.9 vs. 0.4 m), probability of torching (0.45 vs. 0.03), predicted mortality (31% vs. 17% BA), and lower torching (20 vs. 176 km/h) and crowning indices (28 vs. 62 km/h). Upland forests were also significantly more fire prone under current than reconstructed conditions, yet changes in fuels and potential fire behavior were not as large. Under current conditions, riparian forests were significantly more fire prone than upland forests, with greater stand density (635 vs. 401 stems/ha), probability of torching (0.45 vs. 0.22), predicted mortality (31% vs. 16% BA), and lower quadratic mean diameter (46 vs. 55 cm), canopy base height (6.7 vs. 9.4 m), and frequency of fire tolerant species (13% vs. 36% BA). Reconstructed riparian and upland forests were not significantly different. Our reconstruction results suggest that historic fuels and forest structure may not have differed significantly between many riparian and upland forests, consistent with earlier research suggesting similar historic fire return intervals. Under current conditions, however, modeled severity is much greater in riparian forests, suggesting forest habitat and ecosystem function may be more severely impacted by wildfire than in upland forests. 相似文献
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TIAN Xiaorui ZHANG Youhui YANG Sidao ZHONG Youhong .Institute of Forest Protection Chinese Academy of Forestry Beijing P.R.China Tel: --- Fax: --- .Nursery of Guan County Shandong Guan County P.R.China . Forest Public Security Bureau of Guangdong Province Guangzhou P.R.China 《中国林业科技(英文版)》2005,4(2):15-23
Schima superba is a pioneer species for forestation inwildland in tropical and subtropical zones. It can growwell in arid and barren sites and has a strong power ofsprouting from stools. The species has been widelyused for fuelbreak in southern China. In China thefuelbreak is often created by planting broadleaf treesalong the ridge, which is different from the conceptdiscussed in some papers (Agee, et al, 2000; Green,1977; Omi, 1996). In these studies, the shaded fuelbreakwas created by alte… 相似文献
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Prescribed fire is an important tool in the management of ponderosa pine (Pinus ponderosa Dougl. ex Laws.) forests, yet effects on bark beetle (Coleoptera: Curculionidae, Scolytinae) activity and tree mortality are poorly understood in the southwestern U.S. We compared bark beetle attacks and tree mortality between paired prescribed-burned and unburned stands at each of four sites in Arizona and New Mexico for three growing seasons after burning (2004–2006). Prescribed burns increased bark beetle attacks on ponderosa pine over the first three post-fire years from 1.5 to 13% of all trees, increased successful, lethal attacks on ponderosa pine from 0.4 to 7.6%, increased mortality of ponderosa pine from all causes from 0.6 to 8.4%, and increased mortality of all tree species with diameter at breast height >13 cm from 0.6 to 9.6%. On a per year basis, prescribed burns increased ponderosa pine mortality from 0.2% per year in unburned stands to 2.8% per year in burned stands. Mortality of ponderosa pine 3 years after burning was best described by a logistic regression model with total crown damage (crown scorch + crown consumption) and bark beetle attack rating (no, partial, or mass attack by bark beetles) as independent variables. Attacks by Dendroctonus spp. did not differ significantly over bole heights, whereas attacks by Ips spp. were greater on the upper bole compared with the lower bole. Three previously published logistic regression models of tree mortality, developed from fires in 1995–1996 in northern Arizona, were moderately successful in predicting broad patterns of tree mortality in our data. The influence of bark beetle attack rating on tree mortality was stronger for our data than for data from the 1995–1996 fires. Our results highlight canopy damage from fire as a strong and consistent predictor of post-fire mortality of ponderosa pine, and bark beetle attacks and bole char rating as less consistent predictors because of temporal variability in their relationship to mortality. The small increase in tree mortality and bark beetle attacks caused by prescribed burning should be acceptable to many forest managers and the public given the resulting reduction in surface fuel and risk of severe wildfire. 相似文献
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Richy J. Harrod David W. Peterson Nicholas A. Povak Erich K. Dodson 《Forest Ecology and Management》2009
Forest thinning and prescribed fires are practices used by managers to address concerns over ecosystem degradation and severe wildland fire potential in dry forests. There is some debate, however, about treatment effectiveness in meeting management objectives as well as their ecological consequences. The purpose of this study was to assess changes to forest stand structure following thinning and prescribed fire treatments, alone and combined, in the eastern Cascade Mountains of Washington State. Treatments were applied to 12 management units, with each treatment combination replicated three times (including untreated controls). Thinning modified forest structure by reducing overall tree density by >60% and canopy bulk density by 50%, and increased canopy base height by ∼4 m, thereby reducing susceptibility to crown fire. The prescribed fire treatment, conversely, did not appreciably reduce tree density or canopy fuel loading, but was effective at increasing the density of standing dead trees, particularly when combined with thinning (37 snags/ha increase). Prescribed fire effects were more pronounced when used in combination with thinning. Thinning was more reliable for altering stand structure, but spring burning was lower in intensity and coverage than desired and may have led to results that downplay the efficacy of fire to meet forest restoration goals. 相似文献
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Benjamin O. KnappG. Geoff Wang Huifeng HuJoan L. Walker Carsyn Tennant 《Forest Ecology and Management》2011,262(7):1157-1167
Historical land use and management practices in the southeastern United States have resulted in the dominance of loblolly pine (Pinus taeda L.) on many upland sites that historically were occupied by longleaf pine (Pinus palustris Mill.). There is currently much interest in restoring high quality longleaf pine habitats to such areas, but managers may also desire the retention of some existing canopy trees to meet current conservation objectives. However, fast-growing natural loblolly pine regeneration may threaten the success of artificially regenerated longleaf pine seedlings. We evaluated the establishment and growth of natural loblolly pine regeneration following different levels of timber harvest using single-tree selection (Control (uncut, residual basal area ∼16 m2/ha), MedBA (residual basal area of ∼9 m2/ha), LowBA (residual basal area of ∼6 m2/ha), and Clearcut (complete canopy removal)) and to different positions within canopy gaps (approximately 2800 m2) created by patch cutting at two ecologically distinct sites within the longleaf pine range: Fort Benning, GA in the Middle Coastal Plain and Camp Lejeune, NC in the Lower Coastal Plain. The density of loblolly pine seedlings was much higher at Camp Lejeune than at Fort Benning at the end of the first growing season after harvesting. Following two growing seasons, there were no significant effects of canopy density or gap position on the density of loblolly pine seedlings at either site, but loblolly pine seedlings were taller on treatments with greater canopy removal. Prescribed fires applied following the second growing season killed 70.6% of loblolly pine seedlings at Fort Benning and 64.3% of seedlings at Camp Lejeune. Loblolly pine seedlings were generally less than 2 m tall, and completeness of the prescribed burns appeared more important for determining seedling survival than seedling size. Silvicultural treatments that include canopy removal, such as patch cutting or clearcuts, will increase loblolly pine seedling growth and shorten the window of opportunity for control with prescribed fire. Therefore, application of prescribed fire every 2-3 years will be critical for control of loblolly pine regeneration during restoration of longleaf pine in existing loblolly pine stands. 相似文献
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Euro-American logging practices, intensive grazing, and fire suppression have increased the amount of carbon that is stored in ponderosa pine (Pinus ponderosa Dougl. Ex Laws) forests in the southwestern United States. Current stand conditions leave these forests prone to high-intensity wildfire, which releases a pulse of carbon emissions and shifts carbon storage from live trees to standing dead trees and woody debris. Thinning and prescribed burning are commonly used to reduce the risk of intense wildfire, but also reduce on-site carbon stocks and release carbon to the atmosphere. This study quantified the impact of thinning on the carbon budgets of five ponderosa pine stands in northern Arizona, including the fossil fuels consumed during logging operations. We used the pre- and post-treatment data on carbon stocks and the Fire and Fuels Extension to the Forest Vegetation Simulator (FEE-FVS) to simulate the long-term effects of intense wildfire, thinning, and repeated prescribed burning on stand carbon storage.The mean total pre-treatment carbon stock, including above-ground live and dead trees, below-ground live and dead trees, and surface fuels across five sites was 74.58 Mg C ha−1 and the post-treatment mean was 50.65 Mg C ha−1 in the first post-treatment year. The mean total carbon release from slash burning, fossil fuels, and logs removed was 21.92 Mg C ha−1. FEE-FVS simulations showed that thinning increased the mean canopy base height, decreased the mean crown bulk density, and increased the mean crowning index, and thus reduced the risk of high-intensity wildfire at all sites. Untreated stands that incurred wildfire once within the next 100 years or once within the next 50 years had greater mean net carbon storage after 100 years compared to treated stands that experienced prescribed fire every 10 years or every 20 years. Treated stands released greater amounts of carbon overall due to repeated prescribed fires, slash burning, and 100% of harvested logs being counted as carbon emissions because they were used for short-lived products. However, after 100 years treated stands stored more carbon in live trees and less carbon in dead trees and surface fuels than untreated stands burned by intense wildfire. The long-term net carbon storage of treated stands was similar or greater than untreated wildfire-burned stands only when a distinction was made between carbon stored in live and dead trees, carbon in logs was stored in long-lived products, and energy in logging slash substituted for fossil fuels. 相似文献
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There is a lack of knowledge to identify and classify forest structures according to the risk of crown fires, especially in
Mediterranean regions. In this study, for the first time, we use real information, obtained after a wildfire that burnt under
extreme meteorological conditions, to classify forest structures of Pinus halepensis into fuel types as a function of crown fire potential. We identified fourteen forest structures which characterize many forest
types in Western Mediterranean areas depending on canopy closure, number of tree layers, percent of each tree layer and overall
tree density. By using the pattern of fire types that burnt the most numerous forest structures, we have identified four fire
hazard groups of forest structures which are considered different fuel types. The first two had the lowest risk of active
crown fires and they differed in the proportion of surface fires and passive crown fires. The third fuel type was the threshold
between structures with low and high extreme fire behavior; while the fourth had a high risk of active crown fires. Firefighters
and forest managers who are demanding this kind of schema, will test and upgrade this classification of fuel types in function
of crown fire potential during future wildfires. 相似文献
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Using density management diagrams to assess crown fire potential in Pinus pinaster Ait. stands 总被引：1，自引：0，他引：1
Ibán Gómez-Vázquez Paulo M. Fernandes Manuel Arias-Rodil Marcos Barrio-Anta Fernando Castedo-Dorado 《Annals of Forest Science》2014,71(4):473-484