Using routine activity theory to inform a conceptual understanding of the geography of fire events     

《Geoforum》2016

The cost of fire events can be devastating in human, emotional and financial terms. There is a growing realisation that geographical techniques can be used in cross-disciplinary approaches to gain an understanding of potential causation factors associated with such events. Despite this, the theoretical frameworks within which such research efforts are often couched have received relatively scant attention. Contrast this with literature concerned with the geography of crime where the application of routine activity theory in particular has been to the fore in studies concerned with providing a sound conceptual basis to understanding spatial and temporal analysis of crime events. This paper demonstrates the application of routine activity theory to understand the geography of fire events and identify ignition situations incited through behavioural regularities. Further, the paper illustrates the practical utility of routine activity theory and its extensions for designing targeted fire prevention, mitigation and response strategies.  相似文献   

Holocene Vegetation Dynamics, Fire History, Lake Level and Climate Change in the Kootenay Valley, Southeastern British Columbia, Canada     

Douglas J. Hallett  Leonard V. Hills 《Journal of Paleolimnology》2006,35(2):351-371

The environmental history of the Kootenay Valley in the southern Canadian Rockies was reconstructed using lake sediment from Dog Lake, British Columbia, and compared to other paleoenvironmental studies in the region to understand how vegetation dynamics and fire regimes responded to climate change during the Holocene. A pollen-based vegetation reconstruction indicates five periods of vegetation change. At 10,300 cal yr B.P. Pinus-Juniperus parkland colonized the valley and by 7600 cal yr B.P. was replaced by mixed stands of Pinus, Picea and Pseudotsuga/Larix. Fire frequencies increased to their Holocene maximums during the 8200–4000 cal yr B.P. period. From 5500–4500 cal yr B.P. Pseudotsuga/Larix reached its maximum extent in the Kootenay Valley under a more frequent fire regime. At 5000 cal yr B.P. Picea and Abies began to expand in the area and by 4500 cal yr B.P. the forest shifted to a closed montane spruce forest type with dramatically reduced fire frequency. The shift to less frequent forest fires after 4500 cal yr B.P., along with a moisterPicea – dominated closed forest, corresponds to Neoglacial advances in the Canadian Rockies and Coast Mountains. Fire intervals after 4000 cal yr B.P. are significantly longer than the shorter fire intervals of the early to mid Holocene. A return to drier, more open forest condition occurs between 2400–1200 cal yr B.P. with a slight increase in fire activity and summer drought events. Lower lake levels inferred by charophyte accumulation rates during the 2400–1200 cal yr B.P. interval support this moisture regime shift. An abrupt shift toPicea dominated forest occurred from 1200–1000 cal yr B.P. and a final period of wet-closed forest cover reaches its maximum extent from 700–150 cal yr B.P. that appears to be a response to Little Ice Age cooling. Present forests are within their natural range of variability but are predicted to shift again to a drier more open structure with increased Pseudotsuga/Larix cover. More frequent stand replacing fires and increased area burned likely will accompany this change due to continued global warming.  相似文献   

卫星火情探测灵敏度试验与火情遥感新探测通道选择     

戎志国  刘诚  孙涵  马轮基  卢乃锰  刘京晶  张玉香  钟仕全  张艳  张鹏  张甲珅  李亚君  张行清  马瑞升  王君华 《地球科学进展》2007,22(8):866-871

2005年10月在广西武鸣机场进行了一系列的人工火情测量试验。进行的100 m2与200 m2火场同步观测试验表明，在EOS TERRA、EOS AQUA和FY 1D等气象卫星遥感图像的人工火场区，中波红外通道均有明显的增温效应，达到了现行业务火情监测的判识标准，表明气象卫星1 km分辨率的中波红外通道完全可以遥感监测到小至200 m2、甚至100 m2完全燃烧的火场。分析BOMEM MR 154 FT高光谱仪测定的火情光谱特征，发现在中波4.34~4.76 μm光谱段的辐亮度比火情监测常用通道3.5~4.0 μm有更强的响应关系。通过初步的大气辐射传输计算，结果表明此波段似为卫星遥感探测火情更为敏感和有效的通道。  相似文献   

A conceptual model of vegetation dynamics in the semiarid Highland savanna of Namibia, with particular reference to bush thickening by Acacia mellifera     

D.F. Joubert  A. Rothauge  G.N. Smit   《Journal of Arid Environments》2008,72(12):2201-2210

Namibian rangelands are encroached with Acacia mellifera, partially resulting from a poor understanding of vegetation dynamics. A conceptual state-and-transition model of vegetation dynamics in the semiarid Highland savanna in central Namibia, emphasising bush thickening by A. mellifera, is described. Two main states, a grassy and a bushy state, are identified. These are further subdivided, and 11 transitions are identified. The key transition initiating a change from grassy to bushy state can be termed a “leap” (an occasional, infrequent mass recruitment event) following a long “sleep” (no or little change in A. mellifera density). It is rare because it requires three consecutive years of above-average rainfall for seedling establishment. Fire, coinciding with seedling establishment, can interrupt it, while a low biomass grass sward facilitates it. The phenology and physiology of the encroaching species, seed predation and sapling herbivory influence this transition. The model proposes opportunistic management interventions, particularly the use of fire, to minimise the risk of further landscape-scale transitions to a bushy state. It highlights areas where understanding of vegetation dynamics is lacking and recommends crucial research foci. Conceptual models of bush-thickening processes need to account for differences in climate and phenological details of encroaching species.  相似文献   

The effects of vegetative ash on infiltration capacity, sediment transport, and the generation of progressively bulked debris flows   总被引：2，自引：0，他引：2  

Emmanuel J. Gabet  Paul Sternberg 《Geomorphology》2008,101(4):666-673

Through the alteration of the physical characteristics of a landscape, such as the destruction of vegetation and the formation of a hydrophobic layer, a fire can dramatically amplify erosion rates. On the basis of field observations, it has been proposed that the deposition of a layer of ash on the ground surface can enhance the erosion of mountainous terrain by surface runoff and might even be a necessary condition for the generation of progressively bulked debris flows. In this study, a flume was constructed to investigate the role of ash in increasing both the volume and the transport capacity of runoff. The experiments demonstrated that the presence of ash on the soil surface reduces the ability of flowing water to infiltrate; this effect is even greater when the ash has been pre-wetted. In addition, the ability of ash slurries to infiltrate decreases with increasing ash concentration. The results also indicate that the transport capacity of runoff is enhanced by the incorporation of ash into the flow because of the increased fluid density. However, the addition of ash reduces the boundary Reynolds number such that, at high ash concentrations and with fine-grained sediment, sediment transport declines as the flow becomes hydraulically smooth. The experimental results were also used to evaluate the ability of steep flow fronts, a common characteristic of debris flows and flash floods, to increase sediment transport rates. Finally, it is proposed that ash slurries may evolve into progressively bulked debris flows through a positive feedback between fluid density, transport capacity, and erosivity.  相似文献   

Using hyperspectral imagery to predict post-wildfire soil water repellency     

Sarah A. Lewis  Peter R. Robichaud  Bruce E. Frazier  Joan Q. Wu  Denise Y.M. Laes   《Geomorphology》2008,95(3-4):192-205

A principal task of evaluating large wildfires is to assess fire's effect on the soil in order to predict the potential watershed response. Two types of soil water repellency tests, the water drop penetration time (WDPT) test and the mini-disk infiltrometer (MDI) test, were performed after the Hayman Fire in Colorado, in the summer of 2002 to assess the infiltration potential of the soil. Remotely sensed hyperspectral imagery was also collected to map post-wildfire ground cover and soil condition. Detailed ground cover measurements were collected to validate the remotely sensed imagery and to examine the relationship between ground cover and soil water repellency. Percent ash cover measured on the ground was significantly correlated to WDPT (r = 0.42; p-value < 0.0001), and the MDI test (r = − 0.37; p-value < 0.0001). A Mixture Tuned Matched Filter (MTMF) spectral unmixing algorithm was applied to the hyperspectral imagery, which produced fractional cover maps of ash, soil, and scorched and green vegetation. The remotely sensed ash image had significant correlations to the water repellency tests, WDPT (r = 0.24; p-value = 0.001), and the MDI test (r = − 0.21; p-value = 0.005). An iterative threshold analysis was also applied to the ash and water repellency data to evaluate the relationship at increasingly higher levels of ash cover. Regression analysis between the means of grouped data: MDI time vs. ash cover data (R² =0.75) and vs. Ash MTMF scores (R² = 0.63) yielded significantly stronger relationships. From these results we found on-the-ground ash cover greater than 49% and remotely sensed ash cover greater than 33% to be indicative of strongly water repellent soils. Combining these results with geostatistical analyses indicated a spatial autocorrelation range of 15 to 40 m. Image pixels with high ash cover (> 33%), including pixels within 15 m of these pixel patches, were used to create a likelihood map of soil water repellency. This map is a good indicator of areas where soil experienced severe fire effects—areas that likely have strong water repellent soil conditions and higher potential for post-fire erosion.  相似文献   

Performance of geosynthetic reinforced soil bridge abutments with modular block facing under fire scenarios     

《Computers and Geotechnics》2017

This paper investigates the effect of fire on the performance of geosynthetic reinforced soil bridge abutments using experimental tests and finite element analyses. Experimental programs were comprised of a series of tensile strength tests at elevated temperatures and fire resistance tests, which were performed on a physical model. Findings revealed the adverse effect of fire on geosynthetic reinforced soil bridge abutments when fire duration exceeded 60 min. Results show that the depth within the backfill affected by the fire is approximately 50 cm.  相似文献   

A Late Holocene Vegetation and Environment Record from Byenup Lagoon,South-western Australia     

J. R. Dodson  J. J. Lu 《The Australian geographer》2000,31(1):41-54

South-western Australia has a Mediterranean-type climate and its infertile soils support a highly diverse angiosperm flora. Little is known of the vegetation history of this region, and this means that little can be said of the roles of environmental stability, climate change, or human impact on the maintenance or development of the high biodiversity of the region. This study presents a pollen and fossil charcoal record from two peat profiles from a freshwater lagoon region near Lake Muir, east of Manjimup, in south-western Australia. The record shows a glimpse of an early Holocene where a mix of Casuarina and eucalypts with an understorey of heath and some open herbaceous vegetation, including chenopods, occurred. Fire was not an important factor at this time. The main record begins from about 4800 BP, and shows a vegetation mix of Corymbia calophylla and Eucalyptus marginata, with the latter becoming dominant by about 3500 BP. Corymbia calophylla again becomes prominent in the last few centuries. A heathy understorey is present throughout the last 4800 years, but was apparently less dense during phases when C. calophylla was more prominent. Melaleuca woodland has been the main vegetation type around the wetland areas and areas of inundation since the mid-Holocene. Major fire periods at Byenup, around 4200 BP and between about 3000 and 2000 BP, did not result in major vegetation changes. An analysis of cation content in the sediments suggests that weathering and erosion rates have been relatively stable throughout the record, but an increase in phosphorus and possibly organic matter in the surface layers suggests that agricultural practices have led to changes in the chemistry of sediments. It is hypothesised that an increase in effective precipitation about 4800 BP led to the initiation of the continuous part of the sediment record at Byenup. This increase most likely resulted from a more effective westerly wind stream. Changes since this time are more likely a result of changing fire regime and the interaction of species, rather than climate shifts.  相似文献   

基于计算机仿真的火灾时人员安全疏散可靠度分析     

马骏驰  ;李杰  ;周锡元 《地震学刊》2009,(4):376-381

火灾中的人员疏散是个复杂的过程,受到诸多因素的共同影响,传统的人员疏散可靠度分析常常忽略这些因素之间的相互作用。为更准确地计算出火灾中人员疏散的可靠度,本文以某地铁车站为例,借助人员疏散仿真软件buildingEXODUS与火灾模拟程序FDS,分别得到人员所需安全疏散时间（RSET）和可利用安全疏散时间（ASET）。在此基础上,构造人员安全疏散极限状态方程,利用一次二阶矩理论求得安全疏散可靠概率。由于能够较好地反映疏散过程中各影响因素之间的相互作用,因此,采用本文提出的可靠度分析方法能够得到更舍理的结果。  相似文献   

甘肃省森林、草原火灾的成因分析     

李民轩  杨兰芳  韩涛 《干旱气象》1999,(4)

简要介绍了利用NOAA极轨气象卫星资料监测森林 ,草原火灾的原理 ,结合实际工作经验 ,阐明了引起甘肃省森林、草原火灾的成因、林牧区的地理分布及特点  相似文献