首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 265 毫秒
1.
Innumerable forest fire spread models exist for taking a decision, but far less focus is on the real causative factors which initiate/ignite fire in an area. It has been observed that the majority of the forest fires in India are initiated due to anthropogenic factors. In this study, we develop a geo-information system approach for management of forest fire in Mudumalai Wildlife Sanctuary, Tamil Nadu, India, with the objective to develop a forest fire likelihood model, integrating GIS and knowledge-based approach for predicting fire-sensitive initiation areas considering major causative and anti-causative factors. Amongst the various causative factors investigated, it was found that wildlife-dependent factor (antler collection and poaching) contributed significantly to fire occurrence followed by management-dependent factors (uncontrolled tourism and grazing), with much less influence of demographic factors. Similarly, anti-causative factor (stationing of anti-poaching/ fire camps) was considered as quite significant.

The likelihood model so developed, envisaging various factors and flammability, accounted for different scenarios as a result of pair-wise comparison on an ordinal scale in a knowledge matrix. The inferential statistics computed indicated the robustness of the model and its insensitivity to moderate changes. It makes it possible for this forest fire likelihood model to predict and prevent a forest fire in an effective and scientific manner because it can assume forest fire likelihood in real time and present in proper time.  相似文献   


2.
Relatively little is known about vegetation fire regimes in China. In this study, we investigated fire regime characteristics and their potential drivers, utilizing information extracted from the MODerate resolution Imaging Spectrometer (MODIS) satellite. Twelve fire regime variables were selected and computed on a regular grid over all of China, using MODIS burned area and active fire data during the period 2001 to 2016, to identify fire incidence and its inter-annual variability, seasonality, intensity, fire size distribution and vegetation types affected by fire. The variables were normalized and clustered to define six fire regimes with distinctive fire attributes. Results show that 78.6% of the land in China was affected by fire during the study period. The barren or sparsely vegetated lands of western China are nearly fire-free. Active fires were observed in Central China, but area burned was not detectable from MODIS. Forest fires in northeastern China are relatively large, infrequent, with a short fire season that peaks in non-winter seasons and higher inter-annual variability, implying a high likelihood of accidental causes. In contrast, forest fires in southern China are relatively small, frequent, with a long fire season that peaks in non-summer seasons, and lower inter-annual variability, suggesting regular use as a land management tool. Low inter-annual variability and low fire intensity were associated with cropland fires, whereas grassland fires generally exhibit the opposite traits. We have also discussed the potential drivers of each fire regime characteristics.  相似文献   

3.
The main controlling variables for palaeo-landscape evolution are investigated to assess their relative importance using the Gippsland Basin geological history. Palaeo-landscape reconstruction is a complicated process controlled and affected by multiple variables, including tectonic, palaeo-environment, sea-level change, rainfall, sediment erosion, transportation, deposition, etc. The Basin and Landscape Dynamics software (Badlands) software was used with an efficient experimental design (ED) to guide the selected scenarios, process the results, and generate the multi-variate equations that define and identify the important controlling variables. The ED was used to test and identify the main uncertainties and their possible ranges, based on actual field data, while at the same time ensuring that the full multi-dimensional space for those variables was covered to enable the computation of multivariate equations from the minimum number of scenario runs. A full suite of 3D forward palaeo-landscape models of the Gippsland Basin was built to reconstruct the basin history from its formation to the present (Early Cretaceous to Holocene, 137-0 Ma). The models are compared to the corresponding full 3D realistic structural and stratigraphic model of the basin that has been built in Petrel (Schlumberger software). This constrains the sedimentary, stratigraphic, burial and thermal histories to the relative subsidence rates and basin-fill for each geological sequence by using the model isopachs input to the Badlands modelling. The ED required only 22 scenarios to fit 12 identified variables and test for possible interactions with each other. The most significant variables are those that control sediment supply including non-marine erodibility, rainfall, (Rainfall × Area) exponent m, Slope and critical slope while maximum % Marine Deposition and marine dispersal are also required to fill the marine accommodation space. Sea Level and subsidence only become significant when rapid enough to outpace sediment supply. The controlling factors change over time with basin development from rift to post-rift phases and interactions are highly significant.  相似文献   

4.
The short-term (2 years) influence of fire burning with the wind (head fire) and against the wind (back fire) on the productivity (above-ground phytomass and litter) and fire behaviour were determined over seven growing seasons (1995/96–2001/02) in a semi-arid rangeland. The results showed that head fires had significantly greater flame height and rate of spread than back fires. Fire caused a decrease of 40.5% and 22.5% in basal cover for the first and second seasons after burning respectively. The seasonal above-ground phytomass production and litter were significantly decreased by fire over all growing seasons. Seasonal production losses due to fire varied between 225 and 430 kg ha−1. The relation between above-ground phytomass production loss due to fire, and two independent variables namely seasonal rainfall and fuel load (above-ground phytomass plus litter) before burning, were investigated. The multiple linear regression equations obtained for one (r=0.89) and 2 years (r=0.86) after a fire, can be used with great success in estimating seasonal production losses due to fire in semi-arid rangeland.  相似文献   

5.
Abstract

A geographical information system (GIS) approach was used successfully on a federal wilderness area in southwestern Missouri to examine vegetative succession relative to fire management in a glades ecosystem. Maps of vegetation were obtained by interpreting aerial photographs taken in 1938, 1958, 1966, 1975 and 1986. Maps of topography, streams, soils and the location of fires which burned during the period 1938 to 1986 were also procured from a variety of public agencies. All maps were digitized and incorporated into a raster-based GIS with 25 m pixels. It was concluded that (1) both glades and oak-hickory forest have an affinity for distinct physiographic areas and (2) fire can help decrease the rate of processes of natural succession which cause glades to convert to forest. The probable effects of controlled fire on three areas proposed by the Forest Service were evaluated and summarized.  相似文献   

6.
Oblique airborne photogrammetry-based three-dimensional (3D) city model (OAP3D) provides a spatially continuous representation of urban landscapes that encompasses buildings, road networks, trees, bushes, water bodies, and topographic features. OAP3D is usually present in the form of a group of unclassified triangular meshes under a multi-resolution data structure. Modifying such a non-separable landscape constitutes a daunting task because manual mesh editing is normally required. In this paper, we present a systematic approach for easily embedding user-generated content into OAP3D. We reduce the complexity of OAP3D modification from a 3D mesh operation to a two-dimensional (2D) raster operation through the following workflow: (1) A region of interest (ROI) is selected to cover the area that is intended to be modified for accommodating user-defined content. (2) Spatial interpolation using a set of manually controlled elevation samples is employed to generate a user-defined digital surface model (DSM), which is used to reform the ROI surface. (3) User-generated objects, for example, artistically painted road textures, procedurally generated water effects, and manually created 3D building models, are overlaid onto the reformed ROI.  相似文献   

7.
时空因素对中国城市火灾态势变化的影响   总被引：1，自引：0，他引：1  
徐波  王振波 《地理研究》2012,31(6):1143-1156
基于空间动态面板数据模型,对2000～2009年中国市域城市火灾数据进行分析,探讨经济发展与气候变化共同作用下时空因素对中国城市火灾态势变化的宏观影响。结果显示:气候变干促使火灾恶化,而经济发展扭转了这种趋势并促使火灾态势整体改善。时空因素对中国城市火灾态势变化具有显著影响,并可被引申为火灾同化效应、火灾惯性效应、火灾警示效应。火灾安全管理部门应该充分利用这些效应,采取积极措施改善火灾态势。本文补充了城市地理学在城市火灾领域的研究不足;将抽象的时空因素引申为具有实际物理含义的虚拟变量,对相关研究具有借鉴意义。  相似文献   

8.
Effective wildfire management is an essential part of forest firefighting strategies to minimize damage to land resources and loss of human lives. Wildfire management tools often require a large number of computing resources at a specific time. Such computing resources are not affordable to local fire agencies because of the extreme upfront costs on hardware and software. The emerging cloud computing technology can be a cost- and result-effective alternative. The purpose of this paper is to present the development and the implementation of a state-of-the-art application running in cloud computing, composed of a wildfire risk and a wildfire spread simulation service. The two above applications are delivered within a web-based interactive platform to the fire management agencies as Software as a Service (SaaS). The wildfire risk service calculates and provides daily to the end-user maps of the hourly forecasted fire risk for the next 112 hours in high spatiotemporal resolution, based on forecasted meteorological data. In addition, actual fire risk is calculated hourly, based on meteorological conditions provided by remote automatic weather stations. Regarding the wildfire behavior simulation service, end users can simulate the fire spread by simply providing the ignition point and the projected duration of the fire, based on the HFire algorithm. The efficiency of the proposed solution is based on the flexibility to scale up or down the number of computing nodes needed for the requested processing. In this context, end users will be charged only for their consumed processing time and only during the actual wildfire confrontation period. The system utilizes both commercial and open source cloud resources. The current prototype is applied in the study area of Lesvos Island, Greece, but its flexibility enables expansion in different geographical areas.  相似文献   

9.
The Forest Landscape Model (FLM) is an efficiency tool of quantified expression of forest ecosystem''s structure and function. This paper, on the basis of identifying FLM, according to the stage of development, summarizes the development characteristics of the model, which includes the theoretical foundation of mathematical model, FLM of stand-scale, primary development of spatial landscape model, rapid development of ecosystem process model as the priority, and developing period of structure and process driven by multi-factor. According to the characteristics of different FLMs, this paper classifies the existing FLM in terms of mechanism, property and application, and elaborates the identifications, advantages and disadvantages of different types of models. It summarizes and evaluates the main application fields of existing models from two aspects which are the changes of spatial pattern and ecological process. Eventually, this paper presents FLM''s challenges and directions of development in the future, including: (1) more prominent service on the practical strategy of forest management''s objectives; (2) construction of multi-modules and multi-plugin to satisfy landscape research demand in various conditions; (3) adoption of high resolution''s spatial-temporal data; (4) structural construction of multi-version module; (5) improving the spatial suitability of model application.  相似文献   

10.
气候变化、火干扰与生态系统碳循环   总被引：6，自引：0，他引：6       下载免费PDF全文
 随着全球变暖的日益显著,气候变化及其影响越来越受到广泛关注。火干扰作为森林生态系统碳循环的一个重要组成部分,其干扰过程是对碳的再分配过程,因而对区域乃至全球的碳循环产生重要影响。气候变化、火干扰与生态系统碳循环三者之间存在因果循环关系,正确认识气候变化与火干扰的复杂关系及双向反馈作用,以及火干扰在生态系统碳循环中的作用,这对制定科学合理的火干扰管理策略,提高生态系统管理水平,减少碳排放,促进碳增汇,减缓全球变化速率均有重要意义。从两个方面阐述了气候变化、火干扰与生态系统碳循环之间的交互作用关系：气候变化与火干扰相互影响关系及双向反馈作用,分别从气候变化对火干扰的影响及火干扰对气候变化的影响两个方面阐述了两者之间的相互影响关系;火干扰与森林生态系统碳循环的交互作用,分别从火干扰对森林生态系统碳循环的影响及模型方法在模拟火干扰对森林生态系统碳循环影响中的应用两个方面论述火干扰对森林生态系统碳循环的影响及其定量评价模型方法。目前火干扰直接碳排放的模型方法比较完善,而间接影响碳循环的模型方法并不成熟,许多方法局限于定性描述,因此,应进一步探讨集成实地测量、遥感观测和模型模拟的跨尺度火干扰对碳循环的影响研究,注重尺度的转换问题。最后,提出了气候变暖背景下火干扰管理的路径选择,以及对今后的研究方向进行了展望。  相似文献   

11.
选用Landsat 8 资料构建了地表温度（Ts）与归一化植被指数（NDVI）的Ts-NDVI特征空间,计算了温度植被干旱指数（TVDI）。利用MODIS温度产品数据和实地野外采样数据进行精度验证确定煤田火区TVDI阈值。通过对遥感影像的地表热异常信息进行定性与定量分析继而对煤田温度异常区边界信息进行挖掘。结果表明：（1）利用野外实测土壤相对含水量进行验证,反演值与实测值的相关系数R2=0.66,表明干旱指数的反演精度较高,相关性较好。（2）TVDI模型对温度呈现出较高的敏感性,二维散点图集中在1∶1 线上,对NDVI的敏感性较低,有利于识别温度异常区。（3）利用MVC最大合成法,建立TVDI-MVC作为精度验证数据,火区面积为5.03 km2,其中TVDI-SC提取火区精度最大为98.50%,TVDI-SW2提取火区精度最小为88.98%。可见煤田温度异常区范围较广,潜在的灾情恶化较严重。  相似文献   

12.
Two general approaches have been applied to understanding the fractal structure of fluvial topography: (1) deterministic, process-based models, and (2) stochastic partial differential equations (PDE). Deterministic models reproduce the fractal behavior of fluvial topography but have two limitations: they often underestimate the amount of lateral valley and ridge migration that occurs in nature, and the complexity has made it difficult to identify the precise origin of fractal behavior in fluvial landscapes. The simplicity of stochastic PDE models has made them useful for investigating fractal behavior, but they incorrectly suggest that fractal behavior is only possible with stochastic forcing. In this paper I investigate whether simplified, deterministic PDE models of landform evolution also exhibit fractal behavior and other features of complexity (i.e. deterministic chaos). These models are based on the KPZ equation, well known in the physics literature. This equation combines diffusion (i.e. hillslope processes) and nonlinear advection (i.e. bedrock or alluvial channel incision). Two models are considered: (1) a deterministic model with uniform erodibility and random initial topography, and (2) a deterministic model with random erodibility and uniform initial topography. Results illustrate that both of these deterministic models exhibit fractal behavior and deterministic chaos. In this context, chaotic behavior means that valley and ridge migration and nonlinear amplification of small perturbations in these models prevent an ideal steady state landscape from ever developing in the large-system limit. These results suggest that fractal structure and deterministic chaos are intrinsic features of the evolution of fluvial landforms, and that these features result from an inverse cascade of energy from small to large wavelengths in drainage basins. This inverse cascade differs from the direct cascade of three-dimensional turbulence in which energy flows from large to small wavelengths.  相似文献   

13.
Three-dimensional (3D) building models are essential for 3D Geographic Information Systems and play an important role in various urban management applications. Although several light detection and ranging (LiDAR) data-based reconstruction approaches have made significant advances toward the fully automatic generation of 3D building models, the process is still tedious and time-consuming, especially for massive point clouds. This paper introduces a new framework that utilizes a spatial database to achieve high performance via parallel computation for fully automatic 3D building roof reconstruction from airborne LiDAR data. The framework integrates data-driven and model-driven methods to produce building roof models of the primary structure with detailed features. The framework is composed of five major components: (1) a density-based clustering algorithm to segment individual buildings, (2) an improved boundary-tracing algorithm, (3) a hybrid method for segmenting planar patches that selects seed points in parameter space and grows the regions in spatial space, (4) a boundary regularization approach that considers outliers and (5) a method for reconstructing the topological and geometrical information of building roofs using the intersections of planar patches. The entire process is based on a spatial database, which has the following advantages: (a) managing and querying data efficiently, especially for millions of LiDAR points, (b) utilizing the spatial analysis functions provided by the system, reducing tedious and time-consuming computation, and (c) using parallel computing while reconstructing 3D building roof models, improving performance.  相似文献   

14.
Abstract

Fire history reconstructions provide fire managers with valuable information regarding historical fire regime dynamics. Yet, in the Central Hardwood Forest Region (CHF), there is an absence of dendroecological studies where frequent wildfires have persisted into the twenty-first century. This study presents the first documented tree-ring reconstruction of fire history in the Pennsylvania anthracite coal-producing region. An approximately 150-year fire chronology was developed from fire-scarred pitch pine (Pinus rigida) and sassafras (Sassafras albidum) collected on Spring Mountain in Schuylkill County. Principal component analysis and k-means cluster analysis were used to identify four fire regime clusters based on interacting fire and non-fire parameters. Results indicate that fires occurred under a variety of moisture conditions and that a mid-twentieth century increase in fire activity on Spring Mountain was associated with the collapse of the regional anthracite industry and possibly amplified by the 1960s drought. Fires continue to burn on Spring Mountain in the twenty-first century, contrary to the dominant pattern of fire exclusion across the CHF. Future research needs are highlighted regarding historical fire regime dynamics and cultural ties to landscape burning in the Pennsylvania Anthracite Region.  相似文献   

15.
The international standard CityGML defines five levels of detail (LODs) for 3D city models, but only the highest of these (LOD4) supports modelling the indoor geometry of a building, which must be acquired in correspondingly high detail and therefore at a high cost. Whereas simple 3D city models of the exterior of buildings (e.g. CityGML LOD2) can be generated largely automatically, and are thus now widely available and have a great variety of applications, similarly simple models containing their indoor geometries are rare.

In this paper we present two contributions: (i) the definition of a level of detail LOD2+, which extends the CityGML LOD2 specification with indoor building geometries of comparable complexity to their exterior geometries in LOD2; and more importantly (ii) a method for automatically generating such indoor geometries based on existing CityGML LOD2 exterior geometries. We validate our method by generating LOD2+ models for a subset of the Rotterdam 3D data set and visually comparing these models to their real counterparts in building blueprints and imagery from Google Street View and Bing Maps. Furthermore, we use the LOD2+ models to compute the net internal area of each dwelling and validate our results by comparing these values to the ones registered in official government data sets.  相似文献   

16.
Pinyon and juniper have been expanding into sagebrush (Artemisia tridentata) ecosystems since settlement of the Great Basin around 1860. Herbaceous understory vegetation is eliminated as stand densities increase and the potential for catastrophic fires increases. Prescribed fire is increasingly used to remove trees and promote recovery of sagebrush ecosystems. We quantified the effects of prescribed fire, vegetation type, and time following fire on soil KCl extractable nitrogen and NaHCO3 extractable phosphorus in a pinyon–juniper woodland and its associated sagebrush ecosystem immediately before and for 4 years after a spring prescribed burn. Potassium chloride extractable NH4+ and total inorganic-N increased immediately following prescribed fire, and extractable NO3− decreased immediately after the burn. In the surface layer (top 8 cm), extractable NH4+ remained elevated compared to the control through year 2 after the burn. By the first fall post-burn extractable NO3− and total extractable inorganic-N increased and remained elevated over the control through year 3 after the burn in the surface layer. For the entire soil profile (52 cm), the burn had no effect on NH4+, and the effects on total extractable inorganic-N were no longer significant after year 1. However, NO3− remained elevated over the control through year 2 post-fire for the soil profile. Near surface NaHCO3 extractable ortho-P increased immediately following fire, and remained elevated through year 2 post-fire. No fire effects were observed for extractable ortho-P in deeper horizons. Our data show that plant available nitrogen can remain elevated for extended periods following prescribed fire. This can influence regrowth and seedling establishment of native plant species, invasion of exotic plant species and, ultimately, site recovery potential.  相似文献   

17.
About one decade has passed since US vice president Al Gore articulated his vision of Digital Earth (DE). Within this decade, a global multi-resolution and three-dimensional (3D) representation of the Earth, which sums up the DE vision, increasingly gained interest in both public and science. Due to the desired high resolution of the available data, highly detailed 3D city models comprise a huge part of DE and they are becoming an essential and useful tool for a range of different applications. In the past as well as at present, 3D models normally come from a range of different sources generated by professionals, such as laser scans or photogrammetry combined with 2D cadaster data. Some models are generated with semi-automated or fully automated approaches, but in most cases manual fine tuning or even manual construction from architectural plans is required. Further beyond outdoor city models, DE additionally envisages the provision of indoor information. That is, the interior structure of public or publically accessible buildings, such as airports or shopping malls, is represented and made available in 3D; however, at the moment, such models are mostly created by hand and essentially based on professional data sources. In contrast to such professional data, which is mainly captured by surveyors or companies, the last few years revealed the phenomenon of crowdsourced geodata, which receives an increasing attractiveness as an alternative data source for many Geographic Information Systems (GIS). Former research already demonstrated the power and richness of such geodata – especially OpenStreetMap (OSM) – and it has also been proved that this non-standardized, crowdsourced geodata can be combined with international standards of the Open Geospatial Consortium (OGC). For example, CityGML Level-of-Detail 1 (LoD1) and LoD2 models have already been created automatically from OSM. The research presented in this article will further continue on the automated generation of CityGML models from OpenStreetMap. Essentially, a method for the creation of highly detailed CityGML LoD4 models with interior structures will be explained. By applying the invented approach on existing OSM data, limitations and restrictions of the IndoorOSM mapping proposal, the available data and the developed approach are revealed and discussed.  相似文献   

18.
Data from the NASA'S MODIS (Aqua and Terra) and EUMETSAT'S MSG-SEVIRI satellite sensors is analysed to characterise the geographic and temporal (including diurnal) evolution of the July 2007 fire disaster in the Kingdom of Swaziland using a geographic information system (GIS). Significant fire activity was observed during a three-day period beginning on the 27th July 2007. A total of 1358 and 4365 active fire hotpots were detected by MODIS and MSG-SEVIRI, respectively, mainly concentrated in the Highveld (70.91% for MODIS, 89.89% for MSG) and Middleveld (11.27% for MODIS, 5.23% for MSG) with MSG/MODIS active fire count ratio ranging from a high of 3.69 in the Highveld to a low of 0.06 in the Lubombo Plateau. The results indicate complex differences in spatial fire distribution, behaviour and risk within the country and the effect of sensor differences. A pronounced fire diurnal cycle with a broad afternoon peak centred on 14:00 local time is observed, in general agreement with observations from the region. Despite their limitations, the study demonstrates the importance and usefulness of remotely sensed data and GIS technology for fire disaster and risk assessment for a developing country, where fire monitoring resources are scarce.  相似文献   

19.
This research is motivated by the need for 3D GIS data models that allow for 3D spatial query, analysis and visualization of the subunits and internal network structure of ‘micro‐spatial environments’ (the 3D spatial structure within buildings). It explores a new way of representing the topological relationships among 3D geographical features such as buildings and their internal partitions or subunits. The 3D topological data model is called the combinatorial data model (CDM). It is a logical data model that simplifies and abstracts the complex topological relationships among 3D features through a hierarchical network structure called the node‐relation structure (NRS). This logical network structure is abstracted by using the property of Poincaré duality. It is modelled and presented in the paper using graph‐theoretic formalisms. The model was implemented with real data for evaluating its effectiveness for performing 3D spatial queries and visualization.  相似文献   

20.
谭亚平  程承旗  耿晓晖 《地理研究》2012,31(6):1132-1142
随着空间技术和对地观测技术的飞速发展,海量遥感影像索引成为目前国内外学术界和应用部门面临的一大难题,地球剖分系统的产生为这一难题的解决开辟了新的途径。本文首先研究了遥感分景数据的特征和EMD全球剖分的特征,然后针对现有遥感影像数据索引方法的不足,提出了基于EMD剖分系统的三种索引模型:基于影像—面片映射关系的索引模型、基于EMD数据模型的索引和剖分数据标识索引模型,从三个不同的方面探讨了解决索引问题的方法和思路。并给出了利用遥感分景数据的剖分索引模型对线状对象和面状对象进行索引应用的实例。遥感分景数据的剖分索引模型的建立为遥感影像数据的高效存储和索引提供了一种有益的新思路。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号