Modelling forest canopy gaps using LiDAR-derived variables

Remote sensing has revolutionized forest management and has been widely employed to model canopy gaps. In this study, a canopy height model (CHM) and an intensity raster (IR) derived from light detection and ranging (LiDAR) data were used to model canopy gaps within a four-year-old Eucalyptus grandis forest using an object-based image analysis (OBIA) approach. Model thematic accuracies using the CHM, intensity raster and combined data set (CHM and IR) were all above 90%, with KHAT values ranging from 0.88 to 0.96. Independent test thematic accuracies were also above 90%, with KHAT values ranging from 0.82 to 0.91. A comparative area-based assessment yielded accuracies ranging from 70 to 90%, with the highest accuracies achieved using the combined data set. The results of this study show that using a CHM and intensity raster, and an OBIA approach, provides a viable framework to accurately detect and delineate canopy gaps within a commercial forest environment.     

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Optimization of spatial statistical approaches to identify land use/land cover change hot spots of Pune region of Maharashtra using remote sensing and GIS techniques

This study investigated land use/land cover change (LULCC) dynamics using temporal satellite images and spatial statistical cluster analysis approaches in order to identify potential LULCC hot spots in the Pune region. LULCC hot spot classes defined as new, progressive and non-progressive were derived from Gi* scores. Results indicate that progressive hot spots have experienced high growth in terms of urban built-up areas (20.67% in 1972–1992 and 19.44% in 1992–2012), industrial areas (0.73% in 1972–1992 and 3.46% in 1992–2012) and fallow lands (4.35% in 1972–1992 and ?6.38% in 1992–2012). It was also noticed that about 28.26% of areas near the city were identified as new hot spots after 1992. Hence, non-significant change areas were identified as non-progressive after 1992. The study demonstrated that LULCC hot spot mapping through the integrated spatial statistical approach was an effective approach for analysing the direction, rate, spatial pattern and spatial relationship of LULCC.     

基于空间统计分析方法的生态服务价值评价研究

生态服务价值核算对建立可持续发展的土地利用模式至关重要。文中基于地理国情普查试点成果,进行了生态服务价值评估,并在此基础上利用格网分析、Spline插值、Moran’s I、Getis-Ord Gi*等空间统计分析方法,对浙江省德清县生态服务价值进行分析评价。研究结果表明:德清县生态服务价值整体上呈现出集聚现象;单位面积生态服务价值热点主要集中在对河口水库、下渚湖湿地和东部河网密集区等。这些区域直接影响德清县的整体生态环境水平,需要进行重点生态保护。     

夜光遥感支持下的城市人口核密度空间化及自相关分析

基于福建省福州市鼓楼区街道社区人口统计数据、夜光遥感影像、Landsat8影像,融合核密度与回归方程,绘制30 m栅格空间分辨率的人口密度图并进行空间自相关分析。方法:① 采用核密度方法对69个社区人口计算生成人口密度分布图。建立786个居民小区点的人口密度与夜光遥感的常规QQ分位图,检测出人口密度存在较大的误差区域:五凤街道和洪山镇。② 建立人口密度与夜光遥感、Landsat8线性分解的不可渗透表面影像之间的二元二次回归方程,修正两个区域的人口密度误差。③ 采用高/低聚类分析、热点分析、聚类和异常值分析,得到鼓楼区人口高聚类属性,显示了鼓楼区最大商业圈区域与人口密度最大居民点区域,展示了人口聚类的空间局部差异性格局。结果:① 研究中所采用的人口空间化技术融合了2种空间化方法:核密度与回归方程。生成30 m栅格空间分辨率的人口密度图。② 鼓楼区人口密度均值分为3种类型:11 000、25 000和50 000人/ km²,人口密度分布近似正态分布。③ 当鼓楼区人口密度均值大于33 000人/ km²,不可渗透表面灰度值与人口密度相关性更强。反之,夜光亮度值与人口密度相关性更强。     

陕南秦巴山区可持续生计安全评价及其鲁棒性分析

可持续生计安全强调以生态—经济—社会的综合视角来评价欠发达地区的可持续性问题。目前,可持续生计安全分析框架存在权重方法单一和计算结果具有不确定性的问题。选取陕南28个区县,以2005-2014年为时序,运用层次分析法、热点分析和鲁棒性分析分别确定指标权重,定量分析可持续生计安全动力机制和空间聚集性,检验可持续生计安全指数不确定性。结果表明：① 陕南可持续生计安全指数年际差异显著,并逐年增大,其中汉中市差异最为明显,极值均在该市;② 生态安全、经济效益和社会公平综合影响可持续生计安全,影响程度由高到低依次为生态安全>经济效益>社会公平;③ 可持续生计安全整体空间格局表现出“热—冷—热—冷”依次交替的特征,且其发展态势在空间分布上呈现出一定的稳定性,具有明显的地理集中现象;④ 可持续安全指数排名出现频率—变化范围矩阵对角线颜色较深,整体排名出现频率较高,具有较强的鲁棒性,说明可持续生计安全指数及排名稳健性与可信度较高。该研究引入可持续生计安全,可为可持续性评价提供理论方法参考和实践应用借鉴,为欠发达地区可持续发展政策提供科学依据。     

空间尺度对Getis-Ord Gi*获取的CPUE热点模式的影响：以西北太平洋柔鱼为例

空间尺度（渔业网格）不仅影响CPUE全局分布模式,而且影响其局部分布模式及其与海洋环境的关系。在空间多尺度下,本文研究了西北太平洋柔鱼（Ommastrephes bartramii）CPUE热点和冷点分布的尺度关系和尺度效应。将原始渔业数据重采样为从5''×5''到90''×90''的18个空间尺度,以5''的尺度间隔来识别局部聚类簇。论文系统分析了Getis-Ord Gi*热点和冷点的位置、边界、经典统计量随空间尺度的变化。具体地,分析了空间热点和冷点的最小值（Min）、均值（Mean）,最大值（Max）、标准差（SD）、变异系数（CV）、偏度、峰度、第一四分位数（Q1）、中位数、第三四分位数（Q3）、面积和质心等统计量的空间尺度影响。在空间尺度影响分析中,主要考虑线性、对数、指数、幂律和多项式等尺度研究中的常见关系。对于热点和冷点,最大值、标准偏差和峰度具有显著的空间尺度关系,其余统计量一部分在热冷点间存在尺度影响的差异,而另一部分没有明确的尺度关系。研究结果表明,由于不同尺度的热点和冷点的边界和位置与原始尺度的边界和位置明显不同,不建议采用大于30''的网格来分析柔鱼资源的局部空间模式。     

2008-2018年中国手足口病时空分异特征

手足口病是一种在婴幼儿中多发的常见传染病,对儿童的身体健康具有重要影响.为揭示我国手足口病的时空分异特征,为手足口病的防控提供科学依据,本文选取自2008年手足口病被列为丙类传染病以来至2018年中国手足口病发病率为研究数据,运用全局莫兰指数、Getis-Ord Gi*、新兴时空热点分析和标准差椭圆等空间统计方法对中国...     

海南交通可达性的测度与空间分异格局分析

设定交通可达性指数及交通区位优势度、内部交通连通度和对外通达性3个分指数,全面测度海南各县级行政区的交通可达性,在此基础上,采用Global Moran’s I和Getis-Ord G_i^*指数分析与全局趋势分析方法,从多个维度系统研究海南交通可达性空间分异现状格局。结果显示,目前海南各县级行政区交通可达性差异很明显;海南岛交通可达性总体呈沿海内陆分异与北南方向类似U型分异格局,交通可达性的3个分指标均存在鲜明的空间分异特征,即交通区位优势度与交通可达性总体分异格局基本一致,内部交通连通度呈北部较高、中部内陆到西南沿海较低而东南沿海居中的分异格局,对外通达性呈沿海内陆分异及北南和东西方向双重类似U型分异格局;三沙市是海南一个特殊的沿海地级市,其交通可达性很差。地形地貌、经济发展水平、人口和政治因素对海南交通可达性空间分异产生了明显的影响。推进海南经济发展需要充分利用交通条件进行经济空间布局引导,并逐步增强交通布局的空间均衡性。     

Mapping the hotspots and coldspots of ecosystem services in conservation priority setting

Spatial-explicitly mapping of the hotspots and coldspots is a vital link in the priority setting for ecosystem services (ES) conservation. However, little research has identified and tested the compactness and efficiency of their ES hotspots and coldspots, which may weaken the effectiveness of ecological conservation. In this study, based on the RUSLE model and Getis-Ord Gi* statistics, we quantified the variation of annual soil conservation services (SC) and identified the statistically significant hotspots and coldspots in Shaanxi Province of China from 2000 to 2013. The results indicate that, 1) areas with high SC presented a significantly increasing trend as well, while areas with low SC only changed slightly; 2) SC hotspots and coldspots showed an obvious spatial differentiation—the hotspots were mainly spatially aggregated in southern Shaanxi, while the coldspots were mainly distributed in the Guanzhong Basin and Sand-windy Plateau; and 3) the identified hotspots had the highest capacity of providing SC, with 29.6% of the total area providing 59.7% of the total service. In contrast, the coldspots occupied 46.3% of the total area, but only provided 17.2% of the total SC. In addition to conserving single ES, the Getis-Ord Gi* statistics method can also help identify multi-functional priority areas for conserving multiple ES and biodiversity.