基于Kriging的地形高程插值

将地形高程作为区域化变量,根据普通Kriging法由散乱的高程点进行地形高程插值,并采用Matlab软件开发专门的程序,实现研究区高程插值计算与结果可视化分析。以广州市南沙区10 km2范围内的200个高程点数据为例,分别运用球面模型、指数模型和高斯理论变差函数模型进行10 m×10 m格网插值,借助Matlab可视化分析插值结果及其精度,表明采用指数模型效果最好。     

Uncertainty propagation in wildland fire behaviour modelling

Rothermel's model is the most widely used fire behaviour model in wildland fire research and management. It is a complex model that considers 17 input variables describing fuel type, fuel moisture, terrain and wind. Uncertainties in the input variables can have a substantial impact on the resulting errors and have to be considered, especially when the results are used in spatial decision making. In this paper it is shown that the analysis of uncertainty propagation can be carried out with the Taylor series method. This method is computationally cheaper than Monte Carlo and offers easy-to-use, preliminary sensitivity estimations.     

Mapping fire regimes in China using MODIS active fire and burned area data

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.     

Fusing remote sensing with sparse demographic data for synthetic population generation: an algorithm and application to rural Afghanistan

We develop a new algorithm for population synthesis that fuses remote-sensing data with partial and sparse demographic surveys. The algorithm addresses non-binding constraints and complex sampling designs by translating population synthesis into a computationally efficient procedure for constrained network growth. As a case, we synthesize the rural population of Afghanistan, validate the algorithm with in-sample and out-of-sample tests, examine the variability of algorithm outputs over k-nearest neighbor manifolds, and show the responsiveness of our algorithm to additional data as a constraint on marginal population counts.     

Application of geographically weighted regression model in the estimation of surface air temperature lapse rate

The surface air temperature lapse rate(SATLR)plays a key role in the hydrological,glacial and ecological modeling,the regional downscaling,and the reconstruction of high-resolution surface air temperature.However,how to accurately estimate the SATLR in the regions with complex terrain and climatic condition has been a great challenge for re-searchers.The geographically weighted regression(GWR)model was applied in this paper to estimate the SATLR in China's mainland,and then the assessment and validation for the GWR model were made.The spatial pattern of regression residuals which was identified by Moran's Index indicated that the GWR model was broadly reasonable for the estimation of SATLR.The small mean absolute error(MAE)in all months indicated that the GWR model had a strong predictive ability for the surface air temperature.The comparison with previous studies for the seasonal mean SATLR further evidenced the accuracy of the estimation.Therefore,the GWR method has potential application for estimating the SATLR in a large region with complex terrain and climatic condition.     

A hybrid representation for modeling,interactive editing,and real-time visualization of terrains with volumetric features

Terrain rendering is a crucial part of many real-time applications. The easiest way to process and visualize terrain data in real time is to constrain the terrain model in several ways. This decreases the amount of data to be processed and the amount of processing power needed, but at the cost of expressivity and the ability to create complex terrains. The most popular terrain representation is a regular 2D grid, where the vertices are displaced in a third dimension by a displacement map, called a heightmap. This is the simplest way to represent terrain, and although it allows fast processing, it cannot model terrains with volumetric features. Volumetric approaches sample the 3D space by subdividing it into a 3D grid and represent the terrain as occupied voxels. They can represent volumetric features but they require computationally intensive algorithms for rendering, and their memory requirements are high. We propose a novel representation that combines the voxel and heightmap approaches, and is expressive enough to allow creating terrains with caves, overhangs, cliffs, and arches, and efficient enough to allow terrain editing, deformations, and rendering in real time.     

基于地形因子的千米尺度景观生态廊道布局研究

土地利用类型并不是景观类型唯一的描述方式, 生态服务价值的估算和地形指标的纳入更有助于反映景观的空间差异性。应用地形因子与生态价值两类指标, 对关中-天水经济区1 km栅格尺度下生态廊道空间布局形式进行研究, 结果如下:① 相关性分析表明地形因子对生态价值分布有重要影响, 经过统一阈值的脊线谷线提取发现, 对生态价值提取出的高值或低值区域几乎同时也是地形上的山脊线或山谷线, 过渡带基本重合;② 提取山脊生态高值区域作为生境斑块, 通过最大生态阻力进行方向选择, 可得出研究区生态廊道空间布局, 由于廊道宽度可根据物种类型调整, 同时距离较短导致实现难度低, 增删节点与斑块不影响周边网络的拓扑关系, 因此结果应用性相对更强;③ 采用地形和生态服务价值作为衡量指标, 更能体现以像元为单位的景观功能一致性与差异性, 从而也避免了土地利用分类较粗、生境判断难度较大、相同阻力路径过多等一系列问题。本文结果是对千米尺度廊道布局的有效补充。     

提孜那甫河流域地表太阳辐射估算及其影响因素分析

地表太阳辐射是地球表层主要能量来源,对地表能量平衡、能量交换以及生态水文过程等具有决定性意义。山区地形复杂,其地表太阳辐射时空差异较大且较难估算。采用适用于山区的地表太阳辐射模型对西北昆仑山提孜那甫河流域地表太阳辐射时空分布进行了估算,分析了该流域季节太阳辐射空间分布规律并探讨了地形和云2个重要因素对太阳辐射空间分布的影响。结果表明:（1） 地形因子中周围地形阻挡即地形开阔度（Sky view factor,SVF）与年总太阳辐射的关系最为显著,太阳辐射随SVF增加而增加。（2） 年总太阳辐射随着高程增加首先减少,再而随之增加。探究SVF随高程的变化,发现其与太阳辐射随高程的变化趋势较为一致,因此在山区复杂地形下地表太阳辐射估算中仅利用高程对其校正存在明显不足,需综合考虑地形效应。（3） 研究计算了季节云出现频率空间分布与太阳辐射空间分布的相关系数,结果表明夏季太阳辐射受云影响较其他季节显著。定量分析了地形因子以及云对地表太阳辐射空间分布影响的贡献率,周围地形阻挡SVF对地表太阳辐射空间分布的影响最大,高程和云次之。因此综合考虑地形和云对太阳辐射的影响在山区太阳辐射模拟中是非常必要的,研究可为山区地表太阳辐射模拟提供理论依据,并为山区生态水文过程研究提供方法支撑。     

Regional forage production assessment in arid and semi-arid rangelands – A step towards social–ecological analysis

Many of the complex issues worldwide regarding environmental management and sustainable develo-pment require integrating the social and natural sciences. Nevertheless, while theoretical discussions have been increasingly developed, operative issues are still major barriers to integrated social–ecological analysis. The aim of this paper was to assess regional forage production in semi-arid rangelands as a key feature in social-ecological analysis, by using human organizational units (i.e. counties). We used these state-administrative units to explore demographic and farming indicators in order to address socio-productive implications of different regional forage production dynamics. We studied the forage spatial and temporal dynamics in two different large ecological regions: Monte and Patagonia, under a single administrative unit (i.e. province). Since forage production estimations in arid rangelands are not trivial, we tested two different methods. We found that inter-annual variability in forage production explained the main differences between regions. At a regional level, zones with higher temporal variability in forage production registered less rural residents and farm numbers, but inverse situations were registered at sub-regional scales. We found a non-linear relationship between forage production variability and rural population density. We proposed differentiated policy recommendations regarding rangeland management and animal husbandry, considering both the social and ecological contexts.     

Modeling large-scale winter recreation terrain selection with implications for recreation management and wildlife

Winter recreation is a rapidly growing activity, and advances in technology make it possible for increasing numbers of people to access remote backcountry terrain. Increased winter recreation may lead to more frequent conflict between recreationists, as well as greater potential disturbance to wildlife. To better understand the environmental characteristics favored by winter recreationists, and thus predict areas of potential conflict or disturbance, we modeled terrain selection of motorized and non-motorized recreationists, including snowmobile, backcountry ski, and snowmobile-assisted hybrid ski. We used sports recorder Global Positioning System (GPS) devices carried by recreationists at two study areas in Colorado, USA, (Vail Pass and the San Juan Mountains), to record detailed tracks of each recreation type. For each recreation activity, we modeled selection of remotely-sensed environmental characteristics, including topography, vegetation, climate, and road access. We then created spatial maps depicting areas that recreation activities were predicted to select and combined these maps to show areas of potential ecological disturbance or interpersonal conflict between motorized and non-motorized activities. Model results indicate that motorized and non-motorized activities select different environmental characteristics, while still exhibiting some similarities, such as selection for ease of access, reflected in proximity to highways and densities of open forest roads. Areas predicted to have only motorized recreation were more likely to occur further from highways, with greater forest road densities, lower canopy cover, and smoother, less steep terrain, while areas with only non-motorized recreation were closer to highways, with lower forest road densities, more canopy cover and steeper terrain. Our work provides spatially detailed insights into terrain characteristics favored by recreationists, allowing managers to maintain winter recreation opportunities while reducing interpersonal conflict or ecological impacts to sensitive wildlife.     

Reconstructing a cultural fire regime in the Pennsylvania Anthracite Region

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.     

Objective landslide detection and surface morphology mapping using high-resolution airborne laser altimetry

A map of extant slope failures is the most basic element of any landslide assessment. Without an accurate inventory of slope instability, it is not possible to analyze the controls on the spatial and temporal patterns of mass movement or the environmental, human, or geomorphic consequences of slides. Landslide inventory maps are tedious to compile, difficult to make in vegetated terrain using conventional techniques, and tend to be subjective. In addition, most landslide inventories simply outline landslide boundaries and do not offer information about landslide mechanics as manifested by internal deformation features. In an alternative approach, we constructed accurate, high-resolution DEMs from airborne laser altimetry (LIDAR) data to characterize a large landslide complex and surrounding terrain near Christchurch, New Zealand. One-dimensional, circular (2-D) and spherical (3-D) statistics are used to map the local topographic roughness in the DEMs over a spatial scale of 1.5 to 10 m. The bedrock landslide is rougher than adjacent unfailed terrain and any of the statistics can be employed to automatically detect and map the overall slide complex. Furthermore, statistics that include a measure of the local variability of aspect successfully delineate four kinematic units within the gently sloping lower half of the slide. Features with a minimum size of surface folds that have a wavelength of about 11 to 12 m and amplitude of about 1 m are readily mapped. Two adjacent earthflows within the landslide complex are distinguished by a contrast in median roughness, and texture and continuity of roughness elements. The less active of the earthflows has a surface morphology that presumably has been smoothed by surface processes. The Laplacian operator also accurately maps the kinematic units and the folds and longitudinal levees within and at the margins of the units. Finally, two-dimensional power spectra analyses are used to quantify how roughness varies with length scale. These results indicate that no dominant length scale of roughness exists for smooth, unfailed terrain. In contrast, zones with different styles of landslide deformation exhibit distinctive spectral peaks that correspond to the scale of deformation features, such as the compression folds. The topographic-based analyses described here may be used to objectively delineate landslide features, generate mechanical inferences about landslide behavior, and evaluate relatively the recent activity of slides.     

NATIVENESS,INVASIVENESS, AND NATION IN AUSTRALIAN PLANTS*

ABSTRACT. The conceptualization of alien invasive species conflates two axes of variability that have become unhelpfully blurred. The nativeness/alienness axis refers to the presumed belonging of a species in ecological or social space. Invasiveness refers to the behavior of the species in question, particularly in relation to other species. The overlay of nation introduces further variability. Teasing these axes apart is important for more effective environmental management. We examine these concepts using two influential forms of ecological knowledge: the biogeographical and ecological literature and the vernacular experiences of suburban backyarders. Three case studies, the invasive native Pittosporum undulatum and two invasive exotics, Lantana camara and Cinnamomum camphora, illustrate the complex and contingent nature of human interactions with such species and the potential for human interactions to increase and/or reduce the propagation of plant species.     

四川省林草火险等级评价

把四川建设成为长江上游生态屏障是四川省的一项重大战略决策。森林和草地资源防火是生态屏障和生态安全保障体系建设的重要内容。林草火险等级的评价对森林和草地资源的防火具有重要的意义。本文利用遥感、GIS和层次分析法对四川省林草火险等级进行了评价。研究表明,就全省而言,火险等级为5级的占0.8%,为4级的占20.2%,为3级的占47.2%;极高火险区主要出现在甘孜州、凉山州、阿坝州、攀枝花市和雅安市,其所占面积百分比分别为49.2%、24.7%、15.7%、3.5%和3.4%;高火险区主要出现在甘孜州、凉山州和阿坝州,其所占面积百分比共达到了72.1%。建议将甘孜州、凉山州、阿坝州、攀枝花以及雅安市作为四川省林草防火的重点区域,在防火的人、财、物上给予优先考虑。     

Morphometric Comparisons Between Rogen Terrain and Hummocky Terrain

Visual interpretation of aerial photography suggests that certain geomorphological similarities exist between the hummocky terrain of central Alberta, Canada, and the Rogen terrain of Nunavut, Canada. This study statistically compares the two landform types based on measures of depression shapes and ridge orientations. Comparison of depression shapes indicates that two of three sample areas chosen from the hummocky terrain study area are statistically similar to those of the Rogen terrain study area. Analysis of ridge orientations indicates the ridge crests from two of three hummocky terrain sample areas, and ridge crests from within the Rogen terrain study site all exhibit a preferred trend. Variability in the process of formation may explain why only particular areas throughout the hummocky terrain exhibit patterns similar to the Rogen terrain and others do not. Statistical similarities in two-dimensional form between the hummocky terrain of central Alberta and the Rogen terrain of the Northwest Territories however, suggest that these landforms may have a common or similar origin.     

Dynamic hybrid terrain representation based on convexity limits identification

Hybrid digital terrain models combine terrain data with different topologies and resolutions. Cartographic digital terrain models are typically composed of regular grid data that can be locally refined by adding a Triangulated Irregular Network (TIN) that represents morphologically complex terrain parts. Direct rendering of both datasets to visualize the digital terrain model generates discontinuities, as the meshes are disconnected. The utilization of complete/partial precomputed tessellation solutions solves the problem of quality, but limits the applicability of the representation to models with a fixed relative position between datasets. In this paper, we present a new scheme for hybrid terrain representation that permits the dynamic generation of the adaptive tessellation required to join the grid and TIN models. Our proposal permits the dynamic modification of the relative position between datasets. This increases the representation capabilities for those applications where this property is interesting as, for example, urban and landscape planning applications. The algorithm we propose is based on the identification of convex areas on the TIN and the efficient generation of triangles to join the models based on this convex structure. As a result, high quality models without discontinuities are obtained, increasing the flexibility of previous solutions based on fixed precomputations.     

黄土丘陵沟壑区村域生态系统服务簇的时空分异及其地形梯度分析

探究村域生态系统服务簇对于厘清黄土丘陵沟壑区农业生态系统复杂特征、从多重服务供给角度提高服务的福祉贡献具有重要意义。论文以黄土丘陵沟壑区米脂县为例,基于高斯混合模型识别2009年和2019年村域生态系统服务簇并分析其时空分布,同时,结合地形分布指数探究服务簇在地形梯度上的分布模式。结果如下： ① 各类服务空间分异明显,且服务之间空间分布差异较大;近10 a间各类服务水平均有不同程度提高,其中调节服务有较大改善,而食物供给与文化服务增幅较小;各类服务空间变化格局存在较大差异,这与土地利用的空间演变关系密切。② 利用高斯混合模型识别4类服务簇,包括农业生产簇、农业美学簇、生态保育簇与城镇休闲簇;各类服务簇空间分异明显,且研究期间存在明显数量和空间转移变化;农业美学簇与生态保育簇是当地主导服务簇,且主导性增强,而农业生产簇与城镇休闲簇比重下降。③ 地形起伏度与服务簇的空间关联密切。随起伏度上升,农业生产簇与农业美学簇呈倒U型,生态保育簇优势分布增加,城镇休闲簇优势分布减弱;研究期间农业生产簇与城镇休闲簇向低起伏度的转移趋势明显,而农业美学簇与生态保育簇趋向于向高起伏度转移。     

草原火灾风险评价与分区——以吉林省西部草原为例

草原火灾作为自然灾害的一种,是草原地区重要的灾害之一,对我国草原地区的可持续发展有着严重的负面效应。因此进行草原火灾风险评价研究对草原火灾管理显得极为重要。本文依据自然灾害风险分析原理,采用加权综合评分法、层次分析法 (AHP)在综合分析吉林省西部草原火灾的危险性、暴露性、脆弱性和防灾减灾能力的基础上,建立草原火灾风险指数模型 (GFDRI),对研究区草原火灾风险程度进行了定量评价,并借助GIS技术将吉林省西部草原火灾分为轻度 、中度、重度和极重度4个风险区。检验结果证明草原火灾风险评价和分区具有较高的可靠性,可为当地草原防火部门火灾管理和减灾决策的制定提供依据和指导。     

遥感、地图、地理信息系统—体化应用

遥感、地图和地理信息系统（ＯＩＳ）三者呈“你中有我，我中有你”的相辅相成关系．三者一体化应用使地球科学得以进展，又能在资源开发、环境保护、自然灾害监测评价等方面发挥重要作用．一体化应用的基础是掌握三者的学科一技术特性与相通关系．     

Application of FLUENT on fine-scale simulation of wind field over complex terrain

The state-of-art Computational Fluid Dynamics （CFD） codes FLUENT is applied in a fine-scale simulation of the wind field over a complex terrain. Several numerical tests are performed to validate the capability of FLUENT on describing the wind field details over a complex terrain. The results of the numerical tests show that FLUENT can simulate the wind field over extremely complex terrain, which cannot be simulated by mesoscale models. The reason why FLUENT can cope with extremely complex terrain, which can not be coped with by mesoscale models, relies on some particular techniques adopted by FLUENT, such as computer-aided design （CAD） technique, unstructured grid technique and finite volume method. Compared with mesoscale models, FLUENT can describe terrain in much more accurate details and can provide wind simulation results with higher resolution and more accuracy.