共查询到20条相似文献，搜索用时 921 毫秒
1.
Natural disturbances such as fires have been widely studied, but less is known about their spatial ecology than about other aspects of them. We reconstructed and mapped pre–Euro‐American fire history in a subalpine forest landscape in southeastern Wyoming, and analyzed the fires using GIS. Mean fire interval varies little with topography (elevation, aspect, slope) and is spatially autocorrelated at distances of at least 2 km. Fires often spread downslope, and spread more than expected from the north and south and less than expected from the west, under the influence of particular synoptic climatic conditions. The landscape of 1868 a.d., at the time of Euro‐American settlement, was strongly influenced by fires. However, it contained large patches of connected forest and few high‐contrast edges, unlike the modern landscape, which is fragmented by industrial forestry and roads. The spatial ecology of the natural fire regime may be a useful guide for management. 相似文献
2.
KRISHNA PRASAD VADREVU 《Geografiska Annaler: Series A, Physical Geography》2008,90(4):315-328
Vegetation fires are one of the most serious environmental problems in several ecoregions of India. The purpose of this study is to characterize spatio‐temporal characteristics of fire events in Orissa state, eastern India. In this study, ATSR satellite remote sensing data have been used to quantify fire events from 1997 to 2006. The spatial scan statistic that quantifies ‘hotspot’ areas of fire risk has been used to identify statistically significant fire clusters during the ten‐year time period. To assess the causative factors of fires, topographic, vegetation, climatic, anthropogenic and accessibility factors were used in a robust multivariate statistical framework. Results suggested a clear variation in hotspots of fire occurrences among districts. Of the several districts, the most likely cluster of fire events has been identified in Jharsuguda district followed by secondary clusters in Gajapati, Phulbani, Anugul, Debagarh, Balangir and Raygada. The first three principal components (PCs) from multivariate statistical analysis could explain 70.48% of variance in biophysical and socio‐economic indicators of fire events. The loadings were fairly large and highly positive for deciduous forest percentage, elevation, slope mean, aspect mean, and rural population density in the first PC explaining 40.21% of variance. The second PC included drought index, average temperature and illiteracy explaining nearly 19.2% variance. The third PC had a strong positive association with cropped area and forest cover explaining 10.98% of the total variance. Overall, by quantifying the disparities in fire events in space and time, this study demonstrates the utility of the spatial scan statistic in identifying priority areas of fire risk. Our results on fire hotspots and causative factors of risk can guide forest managers toward the best management strategies for avoiding damage to forests, human life, and personal property in the study area. 相似文献
3.
Fire is an important disturbance agent for terrestrial ecosystems, particularly in tropical and subtropical regions where its occurrence is controlled by multiple biophysical and anthropogenic variables. We assessed the temporal and spatial patterns of active fire detections (MODIS product MCD14ML) in the Caribbean region of Colombia between 2003 and 2015, using time series, cross-correlation, hot spot and density techniques. We also assessed the environmental envelope of active fires by evaluating the effect of multiple biophysical and anthropogenic variables on fire presence/absence using generalized linear models (GLMs). Results show that fires follow a clear intra-annual cycle, with 86% of fire events taking place during the region's main dry season (December–March). There is also inter-annual variability related to the Tropical North Atlantic (TNA) quasi-decadal climatic oscillation. Active fires exhibit a distinctive spatial pattern, with regional hotspots. The set of variables that best explain fire presence/absence include biophysical (TNA, temperature annual range, dry quarter precipitation), anthropogenic (minimum distance to towns and roads) and composite (NDVI) variables. The extensive and ongoing land cover transformation of this region, from forest to pasture and agriculture, will likely increase the extent of burned areas and future carbon fire emissions to the atmosphere. 相似文献
4.
中南半岛旱季VIIRS活跃火的空间特征与国别差异 总被引：1，自引：0，他引：1
热带是全球活跃火(active fire)的集中发生区,客观认识其空间特征、国别差异及其动态变化对评估区域生物质燃烧及其碳排放等具有重要意义。作为热带季风气候典型区,中南半岛旱季活跃火发生发展空间特征及其动态变化仍缺乏清晰认识。为此,论文利用可见光红外成像辐射仪(VIIRS) S-NPP 2012—2019年活跃火矢量数据,基于核密度与空间自相关评价了中南半岛及国别旱季尤其是其特征月份(2—4月)活跃火发生发展的密集程度、集聚特征及其动态变化。结果表明：① 中南半岛活跃火核密度低值区占比最大(79%),高值区最小(4%);柬埔寨、缅甸、老挝等经济落后国家的核密度均值明显高于泰国和越南;2012—2019年核密度高值区具有朝高海拔、向内陆与趋边境等分布特征,且柬埔寨东北部长居高值区。② 活跃火核密度中值区变化集中在1—4月,且多分布在低、高值区周围;高值区变化集中在2—4月,由柬埔寨东北部逐渐向缅甸东/西部、泰国西北部以及老挝北/南部转移。③ 半岛与5国活跃火核密度在旱季具有显著空间正相关性,空间集聚类型以“高—高”型和“低—低”型集聚为主,越南、柬埔寨等国局部自相关性强于泰国和老挝。 相似文献
5.
GIS支持下三峡库区秭归县滑坡灾害空间预测 总被引：3，自引：1，他引：2
基于GIS空间分析和统计模型相结合进行区域评价与空间预测是滑坡灾害研究的重要方向之一。以三峡库区秭归县为研究区,选择坡度、坡向、边坡结构、工程岩组、排水系统、土地利用和公路开挖作为评价因子。为提高模型的预测精度、可信度和推广能力,利用窗口采样规则降低训练样本之间的空间相关性。建立Logistic回归模型,对滑坡灾害与评价因子进行定量相关性分析。计算研究区滑坡灾害易发性指数,对其进行聚类分析,绘制滑坡易发性分区图,其中高、中易发区占整个研究区面积的38.9%,主要分布在人类工程活动频繁和靠近排水系统的区域。经过验证,该模型的预测精度达到77.57%。 相似文献
6.
AutoLogistic 方法在土地利用格局模拟中的应用 —— 以张家界市永定区为例 总被引：7，自引：1，他引：6
土地利用/ 土地覆被变化(LUCC) 是当前研究全球变化的重要内容, 而区域土地利用 格局模拟是LUCC 研究的核心内容之一。以张家界市永定区为研究单元, 根据由2005 年土地 利用现状图和数字高程模型数据源得到的土地利用、地形、河流以及道路等空间数据, 对区 域土地利用类型空间格局的空间自相关性特征进行了建模研究, 并通过在传统Logistic 模型 中引入描述空间自相关性的成份, 实现了能够考虑自相关性因素的回归分析模型 (AutoLogistic 模型), 同时应用该模型对区域土地利用格局进行了模拟和分析。结果显示, 通 过与没有考虑空间自相关性的回归模型(传统Logistic 模型) 相比较, 该模型显示了更好的拟 合优度和更高的拟合准确率(耕地、林地、建设用地及未利用地的ROC 值分别从0.851、 0.913、0.877 和0.852 提高到0.893、0.940、0.907 和0.863)。研究结果说明了基于 AutoLogistic 方法的土地利用格局的相关性建模在一定意义上是合理的。同时研究结果也可以 为永定区及其相似地区的土地利用规划决策提供更为科学的依据。 相似文献
7.
Influences of forest roads on the spatial patterns of human- and lightning-caused wildfire ignitions 总被引：1，自引：0，他引：1
Ganapathy Narayanaraj Michael C. Wimberly 《Applied geography (Sevenoaks, England)》2012,32(2):878-888
Understanding the spatial patterns of fire ignitions and fire sizes is essential for understanding fire regimes. Although previous studies have documented associations of human-caused fire ignitions with road corridors, less consideration has been given to understanding the multiple influences of roads on the fire regime at a broader landscape-scale. Therefore, we examined the difference between lightning- and human-caused fire ignitions in relation to forest road corridors and other anthropogenic and biophysical factors in the eastern Cascade Mountains of Washington State. We used geographical information systems and case-control logistic regression models to assess the relative importance of these explanatory variables that influence the locations of lightning versus human-caused ignitions.We found that human-caused ignitions were concentrated close to roads, in high road density areas, and near the wildland-urban interface (WUI). In contrast, lightning-caused ignitions were concentrated in low road density areas, away from WUI, and in low population density areas. Lightning-caused ignitions were also associated with fuels and climatic and topographic factors. A weak but significant relationship between lightning-caused fire and proximity to gravel roads may be related to fuels near roads or to bias in detection and reporting of lightning-caused fires near roads. Although most small fires occurred in roaded areas, they accounted for only a small proportion of the total burned area. In contrast, the large fires in roadless and wilderness areas accounted for most of the burned area. Thus, from the standpoint of the total area burned, the effect of forest roads on restricting fire size is likely greater than the impact of roads on increasing fire ignitions. The results of our study suggest that roads and their edge effect area should be more widely acknowledged as a unique type of landscape effect in fire research and management. 相似文献
8.
Katarina Pavlek Filip Bišćević Petra Furčić Ana Grđan Vesna Gugić Nino Malešić 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2017,117(1):22-35
Wildfires are an important factor of landscape dynamics in fire-prone environments of the world. In the Mediterranean, one of the most fire-susceptible environments globally, between 45,000 and 50,000 wildfires are recorded every year, causing disturbances in forest and grassland ecosystems. As a Mediterranean country, Croatia faces these problems, averaging over 1000 registered wildfires annually, with the coastal areas dominated by forest fires and continental Croatia by fires on agricultural lands. This research combines various landscape and socio-economic factors in the analysis of fire occurrence in Croatia’s southernmost region of Dalmatia. Around 275 of the largest fires (encompassing 98% of the total burnt area) registered in 2013 were investigated using OLS, and different spatial indices were employed to analyse regional variability in fire distribution. The results revealed that areas more prone to fires are the northern inland areas of Dalmatia and its entire coastal zone. Altitude and vegetation type demonstrated a correlation with fire occurrence, but an increase in population in the study area was also correlated with wildfire occurrence. Regarding vegetation, the grasslands and Mediterranean shrubland (maquis) were found to be the most fire-prone vegetation types in the study region, the distribution of which can be linked to different socio-economic and demographic processes occurring in the Eastern Adriatic. 相似文献
9.
The detection of vegetation fires using remote sensing has proven useful for highlighting areas undergoing rapid conversion in humid forests, but not in tropical dry forest (TDF). To further understand this relationship, we explored the correlation between MODIS Active Fires and forest cover change at local scales using 3 × 3 km sampling grids in three TDF landscapes in Bolivia; Mexico, and Brazil. Our analysis showed no single overall correlation among sites between the frequency of fires reported by the MODIS Active Fire Mapping product and forest cover change. Also, aggregated patterns of fire occurrence in Brazil and Bolivia did not correspond to areas with high percentage of forest loss, which indicates that the fire/deforestation relationship in TDF is not apparent in a simple fire frequency map. However, statistically significant correlations were found in sampling boxes with 50–60%, 50–70%, 50–95% forest cover at “initial state” of the time series in the Mexican site, Bolivian site and Brazilian site, respectively. Our findings suggest that complex interactions between anthropogenic fire-use, satellite-detected fires, and deforestation in highly fragmented TDF landscapes are difficult to describe at regional scales and might only be possible to analyze using finer resolution sampling grids. 相似文献
10.
闽东北沿海罗源县土地利用空间分布格局的 多尺度分析 总被引：4，自引：0，他引：4
在不同的空间尺度上,制约土地利用空间分布的影响因子及其影响程度并不相同,因此区域空间分布格局 分析应优先考虑制约空间分布的影响因子识别及其影响程度的尺度依赖性的研究。本文以闽东沿海的罗源县为研 究区域,采样统计方法与GIS 技术,选取20 个候选影响因子,研究了该县主要土地利用空间分布格局的影响因子 及其空间尺度相关性。研究表明模型的解释能力、影响因子及其影响系数均会随研究尺度发生不同程度的变化,回 归模型的解释能力以及主要影响因子的制约程度总体上均随研究尺度增大呈增强趋势。除受坡度、海拔高程等地 形条件的严格制约外,罗源县主要地类均在一定程度上受到人口因素以及若干可达性因素的影响。 相似文献
11.
基于空间滤波方法的中国省际人口迁移驱动因素 总被引：4，自引：5，他引：4
人口迁移数据中往往存在较强的网络自相关性,以往基于最小二乘估计的重力模型与迁移数据的拟合度较低,而改进后的泊松重力模型仍存在过度离散的缺陷,以上问题均导致既有人口迁移模型中的估计偏差。本文构建了特征向量空间滤波（ESF）负二项重力模型,基于2015年全国1%人口抽样调查数据,研究2010-2015年中国省际人口迁移的驱动因素。结果表明：① 省际人口迁移流间存在显著的空间溢出效应,ESF能有效地提取数据中的网络自相关性以降低模型的估计偏差,排序在前1.4%的特征向量即可提取较强的网络自相关信息。② 省际人口迁移流之间存在明显的过度离散现象,考虑到数据离散的负二项重力模型更适用于人口迁移驱动因素的估计。③ 网络自相关性会导致模型对距离相关变量估计的上偏与大部分非距离变量估计的下偏,修正后的模型揭示出以下驱动因素：区域人口特征、社会网络、经济发展、教育水平等因素是引发省际人口迁移的重要原因,而居住环境与公路网络等因素也逐渐成为影响人口迁移重要的“拉力”因素。④ 与既有研究相比,社会网络因素(迁移存量、流动链指数)对人口迁移的影响日益增强,而空间距离对人口迁移的影响进一步呈现弱化趋势。 相似文献
12.
Elevation, timber type, size and density of stand, position on slope, and slope aspect were assessed as to their effects upon the location of 2088 lightning-caused forest fires in a 1.4 million-hectare tract of northern Idaho. χ2 analysis revealed that relative fire frequency was greatest between 1050 and 1650 m on the upper 1/3 of those slopes which lie perpendicular to dominant storm tracks and which are covered with Hemlock, Alpine Fir and Spruce. 相似文献
13.
GIS and ANN model for landslide susceptibility mapping 总被引：1，自引：0，他引：1
XU Zeng-wang 《地理学报》2001,11(3):374-381
Landslide hazard is as the probability of occurrence of a potentially damaging landslide phenomenon within specified period of time and within a given area. The susceptibility map provides the relative spatial probability of landslides occurrence. A study is presented of the application of GIS and artificial neural network model to landslide susceptibility mapping, with particular reference to landslides on natural terrain in this paper. The method has been applied to Lantau Island, the largest outlying island within the territory of Hong Kong. A three-level neural network model was constructed and trained by the back-propagate algorithm in the geographical database of the study area. The data in the database includes digital elevation modal and its derivatives, landslides distribution and their attributes, superficial geological maps, vegetation cover, the raingauges distribution and their 14 years 5-minute observation. Based on field inspection and analysis of correlation between terrain variables and landslides frequency, lithology, vegetation cover, slope gradient, slope aspect, slope curvature, elevation, the characteristic value, the rainstorms corresponding to the landslide, and distance to drainage line are considered to be related to landslide susceptibility in this study. The artificial neural network is then coupled with the ArcView3.2 GIS software to produce the landslide susceptibility map, which classifies the susceptibility into three levels: low, moderate, and high. The results from this study indicate that GIS coupled with artificial neural network model is a flexible and powerful approach to identify the spatial probability of hazards. 相似文献
14.
GIS and ANN model for landslide susceptibility mapping 总被引：4，自引：0，他引：4
XU Zeng-wang 《地理学报(英文版)》2001,11(3):374-381
1 IntroductionThe population growth and the expansion of settlements and life-lines over hazardous areas exert increasingly great impact of natural disasters both in the developed and developing countries. In many countries, the economic losses and casualties due to landslides are greater than commonly recognized and generate a yearly loss of property larger than that from any other natural disasters, including earthquakes, floods and windstorms. Landslides in mountainous terrain often occur a… 相似文献
15.
土地覆被类型空间格局与地形因子的定量关联及其应用 总被引：1，自引：0，他引：1
以全国1∶25万土地覆被数据、全国公里网格DEM数据和县级行政区划数据为基础,首先,在国家尺度上宏观分析地形因子对土地覆被类型空间分布格局的影响,土地覆被类型空间分布宏观格局受海拔高度、坡度、地表起伏度的影响明显,而与坡向的关系并不显著;其次,以县级行政单元为统计分析样本,利用多元线性回归分析方法,在国家和区域两个尺度建立土地覆被类型面积占比与主要地形因子之间的定量模型,在6类土地覆被类型中,除草地以外,其他5类土地覆被类型的面积占比均与地形因子之间呈显著相关关系,显著性由高到低的排列顺序依次为森林、农田、荒漠、聚落和湿地水体;最后,以相关性最好的森林的空间分布为例,说明了将所建立的模型应用于栅格单元上某种土地覆被类型面积占比估算的可能性,虽然估算结果与实际情况存在差异,但总体趋势基本保持一致,特别是土地覆被类型面积占比大的区域。 相似文献
16.
基于遥感技术和GIS的小流域土地利用/覆被变化分析 总被引：36，自引：3，他引：33
根据贵州省平坝县克酬流域1973年MSS影像数据,1989、1995、2000年Landsat TM影像数据,利用RS和GIS信息获取技术、空间分析技术和数理统计方法,分析了该流域土地利用的数量变化和空间变化特征,明确了土地利用变化的主要类型和方向,并探讨了土地利用变化和地形因子的关系。结果显示,该流域土地利用以农田和灌草用地为主,1973~2000年林地和灌草地减少,农田、水域、村镇、交通用地增加,林地转化为灌草、灌草转化为农田及农田转化为村镇居民点和公路用地是研究区主要土地利用变化类型。研究区土地利用空间分布与海拔高程、坡度等地形因子有密切关系。1973~2000年农田、林地和灌草分布的海拔高程和坡度均呈增加趋势,这和上述土地利用类型间的转化规律相一致。 相似文献
17.
18.
19.
于2016年7~12月和2017年4月的旱、雨季期间，以金沙江干热河谷苴那小流域内的银合欢（Leucaena Benth）林地、车桑子（Dodonaea angustifolia）灌丛地和扭黄茅（Heteropogon cantortus）草地为研究对象，通过网格法和土钻法采集并测定了（0~100 cm）土层的土壤含水量，应用经典统计法和地统计学方法分析该区域不同林草植被下坡面土壤水分的动态变化特征。结果表明：（1）研究区土壤含水量总体较低，雨季显著大于旱季，旱、雨季均表现为灌丛地>草地>林地，呈中度至强度变异（0.07~0.28之间）。（2）不同林草植被下旱、雨季土壤水分具有相似的空间自相关性，自相关系数均由正向负转变，但由正向负转变的滞后距离有所不同，且雨季大于旱季，呈中等或强等空间自相关性。（3）不同林草植被下的土壤水分空间结构不同，林地、灌丛地和草地旱雨季最佳拟合模型均为球状模型；相同林草植被下各土层旱、雨季土壤水分的空间分布特征相似，但旱季的分布格局差异更显著，不同林草植被下深层土壤水分分布比表层土壤水分的分布更为复杂，土壤水分呈明显的斑块或条带状分布，含水量高值区和低值区位置不固定。总之不同林草植被类型会改变局部地段土壤水分空间分布，降雨会加强这种差异的趋势，但土壤水分仍具一定空间连续性。 相似文献
20.
Successful implementation of a forest based climate change mitigation mechanism such as REDD + depends on robust and available methods for measurement and estimation of forest degradation. Currently available methods are for application in single-hit degradation incidents in high density humid forests. However, it has been suggested that gradual degradation, especially in dry forests, is more widespread and that methods are needed for measuring and estimating associated emissions. We assess the applicability of an indirect remote sensing approach for monitoring forest degradation: infrastructure and other indicators of human activities are mapped and used for spatial prediction of degradation activities. For proxy variables we tested distance to forest edge, distance to roads, and population pressure calculated as the sum of inhabitants per pixel in the Landscan 2010 population raster dataset multiplied by an inverse power distance decay function. Wood extraction incidents were counted in 160 plots in two dry forests in Tanzania with infrastructural entry from one side only. We analyzed the spatial pattern of forest degradation as a function of the chosen proxy variables using zero inflated count models which allows for an excess of zero counts. A jack-knife bootstrap using 10,000 runs was applied to optimize the population distance decay function. We found that the impact of forest degradation is highest near high population concentration, above 1000 individuals. Furthermore, distance to nearest forest edge or road was a significant proxy for estimation of the number of wood extraction incidents (p < 0.001), where degradation incidents decreased with increasing distance to forest edge or road. At 3000 m from the forest edge towards the forest core the probability of wood extraction is 20% and dropping. The population distance decay function was found to have a steep decline indicating a relative small impact on forest degradation. Further, and perhaps larger, studies are needed to be able to recommend a distance decay function for general application in Tanzania. However, the results are useful for understanding spatial patterns of wood harvesting as a function of distance to nearest forest edge or road in dry Miombo woodland areas with average population pressure at 1685 ± 101 persons within a radius of 4000 m from the wood extraction sites. 相似文献