Long-term influence of fire and harvesting on boreal forest age structure and forest composition in eastern Québec

In boreal forests, historical variations in the area disturbed by natural disturbances or harvesting have rarely been compared. We measured temporal and spatial variations in areas affected by severe fires and clearcutting throughout the 20th century in a 57, 332 km² section of the eastern Canadian boreal forest. We examined the effects of these disturbances on spatio-temporal variations in the abundance of forests >60 years. Natural variability for the abundance of forests >60 years was estimated from simulations of natural disturbance regimes. We also measured compositional and structural differences between three categories of stands originating from relatively recent disturbances (∼50 years; clearcutting, fires, and clearcutting followed by fires), and one category of stands that were undisturbed for at least 200 years. At the regional level, we observed that forests >60 years gradually became scarcer throughout the 20th century due to a gradual expansion of harvested areas, an effect most pronounced in the southern part of the region, where mature and old forest abundance was clearly outside the range of natural variability at the end of the studied period. At the stand level, forest composition and structure differed between stand-origin categories: clearcutting-origin stands contained more balsam fir (Abies balsamea), fire-origin stands more black spruce (Picea mariana), and fire/clearcutting-origin stands more hardwoods (Betula papyrifera and Populus tremuloides). Overall, we estimate that strict forest management targets based on natural disturbance regimes will be difficult to achieve in eastern North-American boreal forests, most notably because contemporary disturbance rates, including both clearcutting and fire, have gradually become higher than the fire rates observed during the preindustrial period.     

Forest natural regeneration and biomass production after slash and burn in a seasonally dry forest in the Southern Brazilian Amazon

This study estimates the aboveground biomass accumulation after forest clearing and slash burning and describes the structure and successional development of the secondary forest in the seasonally dry southern Amazon. The original burn study was conducted in four land clearings in 1997, 1998, and 1999. The size of the clearings varied from 1 to 9 ha. The native forest was felled, allowed to dry for approximately three months and then burned by the end of the dry season. A census was conducted in the central 1-ha forest on each site prior to the area's felling and burn. The aboveground biomass (AGB) and structure were similar to other primary tropical forests. However, the high density of Cecropia spp. before the forest felling and burn treatment indicates past low intensity disturbances. Seven and eight years after the fire, the fallow forests were still in an early successional stage dominated by Cecropia spp. The four areas had a high biomass accumulation during the studied period, varying from 7.5 to 15.0 Mg ha⁻¹ year⁻¹. The lower biomass accumulation in one plot was an effect of a higher fire severity, produced by the one-year difference in time between slash and burn of the forest, slowing the natural regeneration of Cecropia spp. The time needed for this forest to recover to the pre-fire AGB levels ranged from 20 to 30 years, assuming the current AGB accumulation rates are maintained. Considering these results, the maintenance of regenerating secondary forests in the Amazon would be a significant contribution to soil and watershed protection, minimizing biodiversity losses and perhaps mitigating climatic changes effects in the region.     

Forest Fires and Prevention Strategies in Northwestern Region of China

The paper described the natural conditions and forest types in Northwestern Region of China. Most forests in the region are distributed in subalpine areas. It is important to protect the existent forests in the region for maintaining ecological balance. According to the statistics results of 1991~2000, the paper analyzes the forest fires distribution and fire severity. Annually the numbers of forest fires range from 52 to 240. The incidence rate of forest fires in Northwestern Region is under 0.33 per ten thousand ha. There are 0.67-64.4 ha burned area per ten thousand ha forest. The main reasons for forest fires lie in the dry weather conditions, many firebrands, and high fuel loading. The strategies of fire management in the region are to stress the fire education in forest regions, strength the firebrands' management, emphasize the fuel management, and improve the fire monitoring and fire control ability.     

Effect of recurrent fires on soil nutrient dynamics in a tropical dry deciduous forest of Western Ghats,India

The role of forest fires in the soil dynamics and global carbon cycle has not been comprehensively studied in tropical forests as the effects of fire on tropical forest soils can be extremely variable. This study was aimed to understand how repeated fires affect physical and chemical properties of soil in a tropical dry deciduous forest and alter soil fertility and health. The study was carried out in the dry deciduous forest of Mudumalai Tiger Reserve. Soil samples were collected from unburned (B0) to six-time burned (B6) plots. Samples were collected from each plot from three different depths viz. 0–10 (Top), 10–20 (Middle), and 20–30 cm (Bottom) and analyzed for soil physical and chemical properties. Soil pH, EC, WHC decreased with increasing fire frequencies while bulk density increased. Organic Carbon, Total N, and available P decreased with increasing fire frequencies whereas extractable K initially increased but decreased with the very high frequency of fires. NO₃^?N slightly decreased with high fire frequencies but NH₄^?N decreased significantly with increasing fire frequency. These results provide a new insight regarding the influence of repeated fires on soil that will be valuable to understand the effect of fire on the recovery of soils and nutrient dynamics.     

森林火行为与特殊火行为研究进展

森林火灾主要包括地表火、地下火、树冠火3种蔓延形式。目前火蔓延模型主要关注于森林地表火的蔓延研究, 对一些特殊的火行为, 如树冠火、火旋风、飞火等研究极为薄弱, 而这些火行为在特大森林火灾的蔓延传播中起着重要作用, 往往加速火蔓延, 并对扑火人员造成生命危险。我国森林大多集中在山区, 火灾一旦发生, 由于复杂的地形、不均匀的可燃物分布、多变的局地风和林火的相互作用, 极易形成复杂的火行为。文中对森林火灾中的火行为和特殊火行为进行了论述, 讨论了当前的研究进展和未来发展趋势。     

蒙古森林草原火灾状况及林火管理

森林和草原火灾是导致蒙古森林资源下降的主要原因之一,并对其森林造成了严重的影响。蒙古东、南、西三面与中国接壤,大规模火灾导致的越境火对中国的森林和草原构成了严重威胁。文中从森林草原资源概况、火灾特征（包括空间特征、季节特征和火源特征）、火管理模式等方面综述了蒙古森林草原火灾的现状,阐述了其林火管理对中国林火管理的启示。     

福建林火的发生特点与防治对策探讨

对福建省近年发生的１９７起森林火灾归纳、分析表明，森林火灾发生频率最高的是生产用火，林火发生以２、３月份最多；上午１０时至下午１８时为林火发生的高峰；预防林火发生，应确定森林防火戒严期，开展火险预测预报，完善防火设施，以利于迅速扑火。     

The influence of mountain pine beetle outbreaks and drought on severe wildfires in northwestern Colorado and southern Wyoming: A look at the past century

Outbreaks of bark beetles and drought both lead to concerns about increased fire risk, but the relative importance of these two factors is the subject of much debate. We examined how mountain pine beetle (MPB) outbreaks and drought have contributed to the fire regime of lodgepole pine forests in northwestern Colorado and adjacent areas of southern Wyoming over the past century. We used dendroecological methods to reconstruct the pre-fire history of MPB outbreaks in twenty lodgepole pine stands that had burned between 1939 and 2006 and in 20 nearby lodgepole pine stands that were otherwise similar but that had not burned. Our data represent c. 80% of all large fires that had occurred in lodgepole pine forests in this study area over the past century. We also compared Palmer Drought Severity Index (PDSI) and actual evapotranspiration (AET) values between fire years and non-fire years. Burned stands were no more likely to have been affected by outbreak prior to fires than were nearby unburned stands. However, PDSI and AET values were both lower during fire years than during non-fire years. This work indicates that climate has been more important than outbreaks to the fire regime of lodgepole pine forests in this region over the past century. Indeed, we found no detectable increase in the occurrence of high-severity fires following MPB outbreaks. Dry conditions, rather than changes in fuels associated with outbreaks, appear to be most limiting to the occurrence of severe fires in these forests.     

Wildland fires and moist deciduous forests of Chhattisgarh,India: divergent component assessment

We studied moist deciduous forests of Chhattisgarh, India （1） to assess the effect of four levels of historic wildland fire frequency （high, medium, low, and no-fire） on regeneration of seedlings in fire affected areas during pre and post-fire seasons, （2） to evaluate vegetation struc- ture and diversity by layer in the four fire frequency zones, （3） to evalu- ate the impact of fire frequency on the structure of economically impor- tant tree species of the region, and （4） to quantify fuel loads by fire fre- quency level. We classified fire-affected areas into high, medium, low, and no-fire frequency classes based on government records. Tree species were unevenly distributed across fire frequency categories. Shrub density was maximum in zones of high fire frequency and minimum in low- frequency and no-fire zones. Lower tree density after fires indicated that regeneration of seedlings was reduced by fire. The population structure in the high-frequency zone was comprised of seedlings of size class （A） and saplings of size class （B）, represented by Diospyros melanoxylon, Dalbergia sissoo, Shorea robusta and Tectona grandis. Younger and older trees were more abundant for Tectona grandis and Dalbargia sis- soo after fire, whereas intermediate-aged trees were more abundant pre- fire, indicating that the latter age-class was thinned by the catastrophic effect of fire. The major contributing components of fuel load included duff litter and small woody branches and twigs on the forest floor. Total fuel load on the forest floor ranged from 2.2 to 3.38 Mg/ha. The netchange in fuel load was positive in high- and medium-frequency fire zones and negative under low- and no-fire zones. Repeated fires, how- ever, slowly reduced stand stability. An ecological approach is needed for fire management to restore the no-fire spatial and temporal structure of moist deciduous forests, their species composition and fuel loads. The management approach should incorporate participatory forest manage- ment. Use of c     

Change in historic fire disturbance in a Garry oak (Quercus garryana) meadow and Douglas-fir (Pseudotsuga menziesii) mosaic,University of Victoria,British Columbia,Canada: A possible link with First Nations and Europeans

We investigated late Holocene vegetation and fire changes on southeast Vancouver Island, British Columbia, through high-resolution analysis of pollen, spores and charcoal contained within a forest soil. Located in the Mystic Vale Endowment lands, University of Victoria campus, the site occurs adjacent to Garry oak (Quercus garryana) meadows within a Douglas-fir (Pseudotsuga menziesii) forest regionally influenced by First Nations burning. The age of the sequence is estimated from the occurrence of non-native plantain (Plantago spp.) pollen, between the early 19th century and the present. Prior to the 1850s, the Mystic Vale supported a Douglas-fir forest with a sword fern (Polystichum munitum) understory. Low-intensity fires may have burned either at or near the site, but did not destroy the stand. From the time of European settlement (ca. 1850s to 1872) to the early 20th century, Douglas-fir forests with a sword fern understory persisted but with more openings than in the past. Adjacent forests were cleared leading to successional stands of red alder (Alnus rubra). The site may have supported more grasses near or after 1872 because of adjacent cultivation and the introduction of livestock. Local establishment of Garry oaks at the margin of a field adjacent to the deposition site may have occurred at this time. The strong charcoal signal may be attributable to clearing and local fires of European settlers. Exotic weedy species such as plantain arrived during this time. From about the mid 20th century to the present a closed canopy Douglas-fir forest returned. Pre-European charcoal concentrations were significantly greater than modern-day charcoal concentrations. Peak charcoal concentrations coincided with the onset of European settlement in the area, a period in which land-clearing is thought to have been aided by the use of fire. This study suggests that the observed changes in charcoal concentrations in pre- and post-European contact time may be linked with a switch from aboriginal to European ignition sources. The study provides a historical impetus to consider partially restoring parts of southeast Vancouver Island by re-introducing fire via the application of controlled burns.     

Changes in forest structure of a mixed conifer forest, southwestern Colorado, USA

We selected a warm/dry mixed conifer forest (ponderosa pine, white fir, Douglas-fir, and aspen) in southwestern Colorado to reconstruct historical conditions of fire regime and forest structure in preparation for an experiment in ecological restoration. Although mixed conifer forests are of high ecological and social value in the Southwest, they have been less studied than ponderosa pine forests. Fire-scar analysis on a 150-ha area showed recurring fires at mean intervals of 24 years (all fires with minimum of 2 sample trees scarred) to 32 years (fire scarring 25% or more of sample trees) from the 16th century until the abrupt cessation of fire after 1868, concurrent with European settlement. There was no evidence in age or species-specific data of severe burning at the scale of the study blocks (approximately 200 ha). The forest remained unharvested throughout most of the 20th century, until a cut in the early 1990s removed approximately equal basal areas of ponderosa pine and white fir. Forest structure had already changed substantially, however. Total basal area increased from an average of 11 m² ha⁻¹ in 1870 to 27 m² ha⁻¹ in 2003, despite harvesting of at least 8.4 m² ha⁻¹. Ponderosa pine declined from representing nearly two-thirds of basal area in 1870 to one-third in 2003. The other species increased dramatically, especially white fir, which went from 12% to 35% of basal area and dominated stand density with an average of 392 trees ha⁻¹. Total tree density increased from 142 trees ha⁻¹ in 1870 to 677 trees ha⁻¹ in 2003. The ecological changes that occurred here since the 19th century have been in exactly the opposite direction considering the warm, fire-favoring climate expected in the 21st century. If warm/dry mixed conifer forests of southern Colorado are to have a reasonable chance for persistence under the future climate regime, restoring conditions more similar to the frequently burned, open forests of the past is likely to be a useful starting point.     

Forest fire risk assessment in parts of Northeast India using geospatial tools

Forest fire is a major cause of changes in forest structure and function. Among various floristic regions, the northeast region of India suffers maximum from the fires due to age-old practice of shifting culti- vation and spread of fires from jhum fields. For proper mitigation and management, an early warning of forest fires through risk modeling is required. The study results demonstrate the potential use of remote sens- ing and Geographic Information System (GIS) in identifying forest fire prone areas in Manipur, southeastern part of Northeast India. Land use land cover (LULC), vegetation type, Digital elevation model (DEM), slope, aspect and proximity to roads and settlements, factors that influ- ence the behavior of fire, were used to model the forest fire risk zones. Each class of the layers was given weight according to their fire inducing capability and their sensitivity to fire. Weighted sum modeling and ISODATA clustering was used to classify the fire zones. To validate the results, Along Track Scanning Radiometer (ATSR), the historical fire hotspots data was used to check the occurrence points and modeled forest fire locations. The forest risk zone map has 55 63% of agreement with ATSR dataset.     

黑龙江省1980—2005年森林火灾时空特征

森林火灾是林火失去人为控制,在森林内自然蔓延和扩展,对生态系统和人类带来一定危害和损失的森林起火。森林火灾属世界性、跨国性的重大自然灾害,进入20世纪80—90年代以来,全球气候变暖导致森林火灾有上升的趋势,虽然各国的森林防火费用不断增加,但森林火灾发生的面积并未相     

基于INFORM模型与GEE的根河火烧迹地冠层含水量反演研究

[目的]提出一种结合辐射传输模型与遥感云平台反演火烧迹地冠层含水量(Canopy water content,CWC)的新方法,弥补目前对火烧迹地恢复阶段植被含水量的监测,为定量监测植被水分与火灾预警提供理论参考.[方法]以内蒙古自治区根河市火烧迹地为研究对象,基于INFORM辐射传输模型,使用查找表的方法反演森林冠层...     

我国人工林森林可燃物特点及管理技术研究进展

在全球变暖背景下森林火灾发生的危险性持续增加,可燃物是唯一可人为调控的火环境因子.与天然林相比,人工林结构简单,且以富含油脂的纯林为主,同时多为中幼龄林,易发生森林火灾.文中从人工林可燃物特点及其与林火引燃和火行为的角度出发,综述了人工林可燃物管理技术,对管理中存在的问题进行了分析,建议今后人工林可燃物管理在降低森林易...     

火烧迹地形成数量的模型研究

采用抽样调查方法,调查县域火烧迹地数量,研究林业用地中火烧迹地面积比例与针叶林面积比例、针阔混交林面积比例之间的相关规律,建立火烧迹地回归模型.根据研究结果,提出减少森林火灾、减少火烧迹地的对策.     

Evaluating the efficiency of the Dong model in determining fire vulnerability in Iran's Zagros forests

Recent fires in Iran's Zagros forests have inflicted heavy,extensive losses to the environment,forests,villages,and forest inhabitants,resulting in a huge financial loss to the country.With the increasing risk of fire and the resulting losses,it has become ever more necessary to design and develop efficient fire control and prediction procedures.The present study utilizes the Dong model to develop a map of areas vulnerable to fire in the Zarivar lake forests as a representative sample of Zagros forests.The model uses as its inputs some of the most significant factors(such as vegetation,physiographic features,and the human component) that affect the fire occurrence and spread.Having assigned weights to each factor based on the model,all maps were overlapped in the ArcMap and then the region was divided into five zones.The results showed that 74% of the region was located in three classes:highly vulnerable,vulnerable,and medially vulnerable.To validate the proposed zoning map it was compared with a map based on real data obtained from previous fires.The results showed that 81% of fire incidents were located in highly vulnerable,vulnerable and medially vulnerable zones.Furthermore,the findings indicated a medium to a high degree of fire vulnerability in Zarivar Lake forests.     

Quantifying economic losses from wildfires in black pine afforestations of northern Spain

We implemented a fire risk assessment framework that combines spatially-explicit burn probabilities, post-fire mortality models and public auction timber prices, to estimate expected economic losses from wildfires in 155 black pine stands covering about 450 ha in the Juslapeña Valley of central Navarra, northern Spain. A logit fire occurrence model was generated from observed historic fires to provide required fire ignition input data. Wildfire likelihood and intensity were estimated by modeling 50,000 fires with the minimum travel time algorithm (MTT) at 30 m resolution under 97^th percentile fire weather conditions. Post-fire tree mortality due to burning fire intensity at different successional stages ranged from 0.67% in the latest stages to 9.22% in the earliest. Stands showed a wide range of potential economic losses, and intermediate successional stage stands presented the highest values, with about 124 € ha^− 1 on average. A fire risk map of the target areas was provided for forest management and risk mitigation purposes at the individual stand level. The approach proposed in this work has a wide potential for decision support, policy making and risk mitigation in southern European commercial conifer forests where large wildfires are the main natural hazard.