Geomorphology and geochronology of sackung features (uphill-facing scarps) in the Central Spanish Pyrenees

The paper analyses uphill-facing scarps and associated troughs developed in the oversteepened slopes of two neighbouring glacial valleys in the central Spanish Pyrenees. Previous studies of sackung landforms in the Pyrenees have argued for deglacial unloading as the genetic mechanism, but this causal and temporal relationship has not been proved due to the lack of chronological data. The antislope scarps in the two studied locations, Vallibierna and Estós, are developed in Palaeozoic metasedimentary rocks (parallel to the contour lines and the structural grain), occur in the intermediate sector of the hillslope, and are up to 0.5 km long and several meters high. A trench was excavated in a sackung trough fill in each of the valleys in order to gain information about their chronology and genesis. Charcoal from the lowermost unit in Vallibierna provided an age of 5.9 cal. ka for the sackung and extrapolation of the three dates obtained in Estós indicates that the trough formed ca. 7.6–7.8 cal. ka. Deglaciation of the studied sectors of the valleys occurred between 16 and 13 ka. The time lag of >5 ka suggests that glacial erosion and the subsequent debutressing of the oversteepened valley walls created slopes predisposed to sackung development, but did not initiate the movement. Seismic shaking is proposed as a probable triggering factor. This hypothesis, although supported by the sudden deformation event recorded by a failure plane exposed in Vallibierna trench, and by the seismic and neotectonic activity of the area, cannot be proved due to the lack of chronological information about paleoearthquakes.     

Surface sediment characteristics and present dynamics in alluvial fans of the central Spanish Pyrenees

Three alluvial fans in the Ribera de Biescas, upper Gállego Valley, and central Spanish Pyrenees, have been studied in order to explain the most recent changes and to identify the spatial organization of the sediment. In the alluvial fans surveyed, the proximal area is dominated by debris flows, which pass downslope into transitional and fluvial deposits. The relative importance of each type of sediment is closely related to the size and gradient of the alluvial fan, as well as to the gradient in the final stretch of the stream. In general, the size of the sediment decreases from the proximal to the distal area, while the roundness increases. Nevertheless, there are noticeable irregularities in the trend both in longitudinal and transverse transects, due mainly to the sedimentary dynamics of the debris flows, as they advance towards the inner part of each alluvial fan during the most intense peak flows. A sudden shrinkage of the most active area and incision along the fan channels has been assessed and related to land-use changes in the catchments.     

Reconstructing changes in macrophyte cover in lakes across the northeastern United States based on sedimentary diatom assemblages

Macrophytes are a critical component of lake ecosystems affecting nutrient and contaminant cycling, food web structure, and lake biodiversity. The long-term (decades to centuries) dynamics of macrophyte cover are, however, poorly understood and no quantitative estimates exist for pre-industrial (pre-1850) macrophyte cover in northeastern North America. Using a 215 lake dataset, we tested if surface sediment diatom assemblages significantly differed among lakes that have sparse (<10% cover; group 1), moderate (10–40% cover; group 2) or extensive (>40% cover; group 3) macrophyte cover. Analysis of similarity indicated that the diatom assemblages of these a priori groups of macrophyte cover were significantly different from one another (i.e., difference between: groups 1 and 3, R statistic = 0.31, P < 0.001; groups 1 and 2, R statistic = 0.049, P < 0.01; groups 3 and 2, R statistic = 0.112, P < 0.001). We then developed an inference model for macrophyte cover from lakes classified as sparse or extensive cover (145 lakes) based on the surface sediment diatom assemblages, and applied this model using the top-bottom paleolimnological approach (i.e., comparison of recent sediments to pre-disturbance sediments). We used the second axis of our correspondence analysis, which significantly divided sparse and extensive macrophyte cover sites, as the independent variable in a logistic regression to predict macrophyte cover as either sparse or extensive. Cross validation, using 48 randomly chosen sites that were excluded from model development, indicated that our model accurately predicts macrophyte cover 79% of the time (r ² = 0.32, P < 0.001). When applied to the top and bottom sediment samples, our model predicted that 12.5% of natural lakes and 22.4% of reservoirs in the dataset have undergone a ≥30% change in macrophyte cover. For the sites with an inferred change in macrophyte cover, the majority of natural lakes (64.3%) increased in cover, while the majority of reservoirs (87.5%) decreased in macrophyte cover. This study demonstrates that surface sediment diatom assemblages from profundal zones differ in lakes based on their macrophyte cover and that diatoms are useful indicators for quantitatively reconstructing changes in macrophyte cover.     

Prediction of landslide susceptibility using rare events logistic regression: A case-study in the Flemish Ardennes (Belgium)

In this article a statistical multivariate method, i.e., rare events logistic regression, is evaluated for the creation of a landslide susceptibility map in a 200 km² study area of the Flemish Ardennes (Belgium). The methodology is based on the hypothesis that future landslides will have the same causal factors as the landslides initiated in the past. The information on the past landslides comes from a landslide inventory map obtained by detailed field surveys and by the analysis of LIDAR (Light Detection and Ranging)-derived hillshade maps. Information on the causal factors (e.g., slope gradient, aspect, lithology, and soil drainage) was extracted from digital elevation models derived from LIDAR and from topographical, lithological and soil maps. In landslide-affected areas, however, we did not use the present-day hillslope gradient. In order to reflect the hillslope condition prior to landsliding, the pre-landslide hillslope was reconstructed and its gradient was used in the analysis. Because of their limited spatial occurrence, the landslides in the study area can be regarded as “rare events”. Rare events logistic regression differs from ordinary logistic regression because it takes into account the low proportion of 1s (landslides) to 0s (no landslides) in the study area by incorporating three correction measures: the endogenous stratified sampling of the dataset, the prior correction of the intercept and the correction of the probabilities to include the estimation uncertainty. For the study area, significant model results were obtained, with pre-landslide hillslope gradient and three different clayey lithologies being important predictor variables. Receiver Operating Characteristic (ROC) curves and the Kappa index were used to validate the model. Both show a good agreement between the observed and predicted values of the validation dataset. Based on a qualified judgement, the created landslide susceptibility map was classified into four classes, i.e., very high, high, moderate and low susceptibility. If interpreted correctly, this classified susceptibility map is an important tool for the delineation of zones where prevention measures are needed and human interference should be limited in order to avoid property damage due to landslides.     

Assessment of ski condition reliability in the Spanish and Andorran Pyrenees for the second half of the 20th century

In this study temporal trends of 14 climate and snow parameters related to ski conditions were analyzed for 11 ski stations located in the central Pyrenees (Spain and Andorra). We also investigated whether there was a temporal association for the analyzed parameters, such that the occurrence in a particular year of good (or bad) climate or snow conditions as represented by one parameter was similarly reflected by the other parameters. The lack of reliable climate and snow measurements was overcome by the use of simulated climate data retrieved from a high resolution hindcast simulation available for the period 1960–2006. These data were also used as inputs for an energy and mass snow energy model to obtain snow series. The results showed trends in ski reliability parameters for the 1960–2006 period. The number of days having a snowpack deeper than 30 cm and 100 cm showed declines at low and mid altitudes. The start of the ski season appears progressively delayed for all stations, and the ski season shortened. The frequency of rainy days increased at 3 stations and decreased at 8, while the frequency of days having heavy snowfall increased at 8 stations and declined at 3. Days having potential for snowmaking declined at all stations. The number of days having a wind-chill < −20 °C also decreased markedly, as overall did the number of days having a wind speed greater than 80th percentile. The main findings from the assessment of temporal associations between climate and snow parameters were positive correlations between snow depth and windy conditions. Seasons having a higher frequency of very cold days had a lower frequency of heavy snowfall and rainy days. Thus, the adverse effects on the ski industry of lesser snow availability may have been partially negated by the occurrence of fewer days of closure because of high winds, or other adverse meteorological factors.     

Changes in land use/cover mapped over 80 years in the Highlands of Northern Ethiopia

Despite many studies on land degradation in the Highlands of Northern Ethiopia, quantitative information regarding long-term changes in land use/cover (LUC) is rare. Hence, this study aims to investigate the LUC changes in the Geba catchment (5142 km²), Northern Ethiopia, over 80 years (1935–2014). Aerial photographs (APs) of the 1930s and Google Earth (GE) images (2014) were used. The point-count technique was utilized by overlaying a grid on APs and GE images. The occurrence of cropland, forest, grassland, shrubland, bare land, built-up areas and water body was counted to compute their fractions. A multivariate adaptive regression spline was applied to identify the explanatory factors of LUC and to create fractional maps of LUC. The results indicate significant changes of most types, except for forest and cropland. In the 1930s, shrubland (48%) was dominant, followed by cropland (39%). The fraction of cropland in 2014 (42%) remained approximately the same as in the 1930s, while shrubland significantly dropped to 37%. Forests shrank further from a meagre 6.3% in the 1930s to 2.3% in 2014. High overall accuracies (93% and 83%) and strong Kappa coefficients (89% and 72%) for point counts and fractional maps respectively indicate the validity of the techniques used for LUC mapping.     

Incorporating spectral data into logistic regression model to classify land cover: a case study in Mt. Qomolangma (Everest) National Nature Preserve

Only few models for land-cover classification incorporated spectral data into ordinary logistic regression (OL model) in the Mt. Qomolangma (Everest) National Nature Preserve (QNNP) in China. In this study, spectral variables were incorporated into OL model and autologistic regression (AL) model to classify six main land covers. Twelve environmental variables and seven spectral variables of 10,000 stratified random sites in the QNNP were quantified and analyzed; OL model, AL model, OL model with spectral data (OLM model), and AL model with spectral data (ALM model) were estimated. The OLM and ALM models produced better estimates of regression coefficients and significantly improved model performance and overall accuracy for the grassland, sparsely vegetated land, and bare land compared with OL and AL models.     

GIS techniques for regional-scale landslide susceptibility assessment: the Sicily (Italy) case study

This study describes the assessment of landslide susceptibility in Sicily (Italy) at a 1:100,000 scale using a multivariate logistic regression model. The model was implemented in a GIS environment by using the ArcSDM (Arc Spatial Data Modeller) module, modified to develop spatial prediction through regional data sets. A newly developed algorithm was used to automatically extract the detachment area from mapped landslide polygons. The following factors were selected as independent variables of the logistic regression model: slope gradient, lithology, land cover, a curve number derived index and a pluviometric anomaly index. The above-described configuration has been verified to be the best one among others employing from three to eight factors. All the regression coefficients and parameters were calculated using selected landslide training data sets. The results of the analysis were validated using an independent landslide data set. On an average, 82% of the area affected by instability and 79% of the not affected area were correctly classified by the model, which proved to be a useful tool for planners and decision-makers.     

大城市内部连锁超市空间分布格局及其区位选择——以南京市苏果超市为例

连锁超市已成为中国大城市内部零售商业的主要业态。针对目前研究中对城市内部尺度连锁超市空间布局问题关注不足,本文以南京市苏果超市为例,从空间格局演化、集聚分布状况、不同类型超市的区位选择等方面进行分析。研究方法包括点模式分析、空间密度分析和空间自相关分析等。结果发现:南京市苏果超市的空间总体分布呈中心到外围递减的倒"U"型集聚特征;不同类型苏果超市的分布特征不同,华润卖场的空间分布相对分散,社区店、便利店的分布相对集聚;空间分布热点呈蔓延扩散与等级扩散混合模式。运用Binary Logistic二分逻辑回归对影响超市区位选择的因素进行计量分析,结果表明经济发展情况、消费者规模、交通通达性、居民购买力、城乡差别、公司战略等多种因素,通过综合作用机制,共同推动了南京市苏果超市的空间分布格局。     

民间信仰载体的地域格局及其影响因素——以兰州市榆中县祠庙文化为例

以祠庙祭祀为主体且祠庙保存良好的民间信仰是甘肃陇中地区民间文化的重要组成。甘肃陇中地区的民间信仰具有很强的趋同性,本文以陇中地区的榆中县为例,以各村的祠庙为民间文化载体,通过核密度分析、Logistic回归等方法探讨榆中县民间文化载体的空间分布及其影响因素对于探讨陇中地区人地关系,保护和弘扬民俗文化有着重要意义。研究结果表明：（1）根据已有研究将榆中县民间信仰归纳为山神信仰、水神信仰、天地信仰、女性信仰、英雄崇拜和祖先崇拜,祖先崇拜的祠庙数量占有重要地位;（2）榆中县祠庙主要分布在西北黄河南岸、中部陇海铁路沿线及南部风景名胜集聚区,村级层面空间差异不显著、乡镇空间差异相对较大。通过核密度分析,不同类别民间信仰空间分布热点各有不同;（3）榆中县民间信仰空间分布受到区位条件限制,民间信仰的祠庙多位于海拔高度较低、人口密度较大、交通可达性较好的地区,坡度和到水源的距离成为山神信仰和水神信仰祠庙空间分布显著的影响因子,榆中县祠庙呈现出山神信仰类祠庙“依山”,水神信仰类祠庙“傍水”的空间特点。     

Concrete evidence & geographically weighted regression: A regional analysis of wealth and the land cover in Massachusetts

Several studies indicate that there is a positive relationship between green vegetation land cover and wealthy socio-economic conditions in urban areas. The purpose of this research is to test for and explore spatial variation in the relationship between socio-economic and green vegetation land cover across urban, suburban, and rural areas, using geographically weighted regression (GWR). The analysis was conducted at the census block group level for Massachusetts, using Census 2000 data and impervious surface data at 1-m resolution. To explore regional variations in the relationship, four scenarios were generated by regressing each of the following socio-economic variables – median household income, percentage of poverty, percentage of minority population, and median home value – against two environmental variables – percent of impervious surface and population density. GWR results show that there is a considerable spatial variation in the character and the strength of the relationship for each model. There are two main conclusions in this study. First, the impervious surface is generally a strong predictor of the level of wealth as measured by four variables included in the analysis, at the scale of census block group; however, the strength of the relationship varies geographically. Second, GWR, not ordinary least squares technique, should be used for regional scale spatial analysis because it is able to account for local effects and shows geographical variation in the strength of the relationship.     

Assessing the implications of the recent community opening policy on the street centrality in China: A GIS-based method and case study

Recently, the Chinese government raised an urban planning policy which suggests communities open their private roads for public transport and establish street networks with high spatial density in cities. In this context, the purpose of this study is to analyze the potential changes to street network accessibility using GIS techniques and to provide spatial information that may influence the decision making of urban managers. In addition to the existing street network data in the case study city, Shenzhen, intra-community roads are extracted from building footprints in GIS topographic database and used to construct a potential street network with respect to the community opening policy. An automatic GIS-based method is proposed here to analyze the location advantage information in the simulated urban environment, by combining Delaunay triangulation model and graph theory concepts. Specifically, we establish a two-step framework based on the spatial relationships between roads and buildings. Firstly, intra-community roads between neighboring building footprints are generated using a Delaunay triangulation skeleton model, and with the existing inter-community roads they form the simulated network. Secondly, street centrality indices of the current and simulated networks are compared in terms of closeness, betweenness and straightness. Results indicate that after applying the policy the global accessibility in the city would be increased at some places and decreased at others, and places' directness among others would be generally improved. In addition, the skeleton of central routes for through traffic would not change much. The presented method can also be applied to other cities.     

A case study of land cover change (1950-2003) and runoff in a Mediterranean catchment

Mediterranean environments have been subject to major land cover change since the end of the second world war. Housing, agricultural activities, forests, green spaces and other land uses have shifted due to urbanisation and tourism. These changes influence runoff, and municipal authorities often cannot estimate the net impact of complex land cover transitions. During this period, elected representatives have become increasingly sensitive to the risks of flooding and have implemented a number of channel management strategies. The main objective of this case study was to analyse the impact of land cover change on total storm runoff between 1950 and 2003 in a Mediterranean catchment near St Tropez, France. A secondary objective was to compare these changes to the impacts of channel management on bankfull discharge. Aerial photographs were used to classify land cover in 3 urban categories, vineyards and bare soil, forests, and green spaces. Stream discharge was estimated using a distributed event based total runoff approach. After validating the model for a large winter event (114 mm) for 1982, runoff was calculated for the same event for 1950 and 2003. Land cover changes occurred mainly in the alluvial plain area. Total gauge catchment urban area increased from 30.1 ha to 393.8 between 1950 and 2003 at the expense mainly of agricultural land, but this was compensated in part by an increase in grassed area. Some of the loss in vineyards was replaced by clearing forested land on the first hills close to the plain. Bank stabilisation and channel maintenance since the 1980’s reduced surface roughness and increased channel area, thereby greatly increasing bankfull discharge. While the impact of urbanisation on runoff was small, channel management effects increased bankfull discharge substantially. Flood damage from extreme events was not studied here.     

人工绿洲生态系统中土壤和植被对土地利用变化的响应——以北屯绿洲为例

在遥感(RS)和地理信息系统(GIS)技术的支持下,对干旱区典型人工绿洲-北屯绿洲1989和2005年两期遥感影像进行了处理,分析了绿洲16年来的土地利用/覆盖变化.通过野外调查、实验室分析及"时-空替代法"等方法,对人工绿洲生态系统中的土壤和植被对LUCC的响应机制进行了分析.结果表明:(1)北屯绿洲耕地和盐碱沼泽地面积不断增加,垦荒和撂荒成为土地利用变化的两个主要过程.(2)绿洲土地利用变化对土壤养分和pH值的影响显著.(3)耕地的土壤盐分含量低于弃耕地和荒地.(4)随着土地利用类型的变化,群落组成发生较大变化,优势种更替明显.     

An analysis of oasis evolution based on land use and land cover change: A case study in the Sangong River Basin on the northern slope of the Tianshan Mountains

This study investigated oasis evolution and the changes of peripheral desert in the Sangong River Basin since the 1950s by rebuilding seven land cover maps derived from black-and-white aerial photographs (1958, 1968, and 1978), a color-infrared aerial photograph (1987), Landsat Thematic Mapper (TM) imagery (1998), Satellite Pour l’Observation de la Terre (SPOT) imagery (2004), and Landsat Operational Land Imager (OLI) imagery (2014). The results showed that: (1) Since 1950, the oasis consecutively expanded more than four times from an alluvial fan to an alluvial plain, causing the shrinkage of desert landscapes that were dominated by a Haloxylon ammodendron Bunge community (HBC) and a Tamarix chinensis Lour community (TLC). Furthermore, the primary (1958–1968) and final (2004–2014) stages were the most important periods, during which agricultural land experienced the most rapid expansion during the period 1958–1968, and the built-up area showed the most rapid expansion after the 2000s. (2) Two basic management modes, a “local mode” formed by the local governments and a “farm management mode” developed by Xinjiang Production and Construction Corps, together promoted oasis evolution under various land-use and landcover (LULC) stages. (3) The evolution of the modern oasis during the 1950s–2004 showed the general features of an arid oasis, while during the period of 2004–2014 it was characterized by a large-scale inter-basin water diversion or the import of new water sources. (4) The oasis expanded at the expense of desert vegetation, resulting in distinct variation in the structure of the desert plant community, which will make it more difficult to protect the desert ecosystem.     

首套全球30 m分辨率土地覆被产品区域尺度精度评价——以河南省为例

以河南省为研究区,对全球首套30 m分辨率土地覆盖产品GlobleLand30进行区域尺度精度评价。首先,以中国1\begin{array}{c}:\end{array}10万土地利用数据（CHINA-2010）为参考,分析两种产品的空间一致性;而后,通过Google Earth样本分析GlobleLand30在空间不一致区域的制图精度;最后,利用野外实地考察样本对GlobleLand30进行总体精度评价,并从土地覆被复杂度、高程等方面分析影响精度的原因,结果表明：① GlobleLand30与CHINA-2010空间一致性达80.20%。两种产品对耕地、林地、人工地面一致性高,对草地、水体、灌木、湿地、未利用土地的一致性低。② 在空间不一致区域,GlobleLand30的总体分类正确率略低于CHINA-2010,但两者对不同地类的优势不同。③ 经野外实地考察验证可知,GlobleLand30的总体精度达83.33%。④GlobleLand30与CHINA-2010的空间一致性随土地覆被复杂度的增加而降低,并在高程过渡带较低。     

多中心城市群土地利用/覆被变化地学信息图谱研究——以长株潭城市群为例

多中心城市群具有交通网络发达、功能联系密切、空间多维复合等特征,其土地利用/覆被变化（LUCC）是一个相当复杂的过程。采用地学信息图谱方法,探索城市群LUCC数量结构与时空格局一体化耦合机理,研究用地变化与区域发展互动关系,有助于深入揭示多中心城市群土地利用时空演变规律,为同类城市群的国土空间规划和健康发展提供参考。本文以典型案例长株潭城市群为例,构建1995—2015年四个时期地学信息图谱,并耦合重心转移模型,在总体量化分析基础上,重点从城际与城乡视角深入解析城市群土地利用时空变化特征和一体化发展态势。研究结果表明：① 土地利用总体动态加速演变。四期建设用地扩张年动态度分别为1.06、4.10、2.21和7.39,转移强度动态增加,耕地和林地呈加速减少态势。② 城际与城乡地类图谱转移呈现多维演变。图谱“15（耕地→建设用地）、25（林地→建设用地）、45（水域→建设用地）”重心由株洲城区（Ⅰ 期）向长沙城区（Ⅱ 期和Ⅲ 期）再向湘潭城区（Ⅳ期）迁移,经历“相对均衡-长沙加速崛起-有机均衡”和“城市加速集聚-城乡相对均衡”演变过程。③ 近年来,城际转移强度差异缩小,转移结构分异增加,区域主体功能逐步凸显。同时,外围区县加速发展,城乡一体化水平明显提升。④ 城市群土地利用涨落势图谱与经济社会一体化发展高度耦合,同时耕地保护与高质量发展有待加强。     

Paleolimnological evidence for increased landslide activity due to forest clearing and land-use since 3600 cal BP in the western Swiss Alps

Schwarzsee is located in the western Swiss Alps, in a region that has been affected by numerous landslides during the Holocene, as evidenced by geological surveys. Lacustrine sediments were cored to a depth of 13 m. The vegetation history of the lake's catchment was reconstructed and investigated to identify possible impacts on slope stability. The pollen analyses record development of forest cover during the middle and late Holocene, and provide strong evidence for regional anthropogenic influence such as forest clearing and agricultural activity. Vegetation change is characterized by continuous landscape denudation that begins at ca. 4300 cal. yrs BP, with five distinct pulses of increased deforestation, at 3650, 2700, 1500, 900, and 450 cal. yrs BP. Each pulse can be attributed to increased human impact, recorded by the appearance or increase of specific anthropogenic indicator plant taxa. These periods of intensified deforestation also appear to be correlated with increased landslide activity in the lake's catchment and increased turbidite frequency in the sediment record. Therefore, this study gives new evidence for a strong influence of vegetation changes on slope stability during the middle and late Holocene in the western Swiss Alps, and may be used as a case study for anthropogenically induced landslide activity.     

地理区位与权力——以广州市X市场为例

从人本主义视角,以广州x市场为个案,以权力为主线,揭示地理区位和社会系统的内在关系。研究表明：（1）地方权力关系适度嵌入地理区位,地理区位具有权力依赖指向。（2）权力空间化下的地理区位具有不确定性。市场是作为客体而存在的,地理区位更多的是体现了精英的主体性,精英群体权力的空间化控制、建构或者瓦解着市场。权力空间的生产性...     

CLUE-S模型的改进与土地利用变化动态模拟——以张家界市永定区为例

区域土地利用变化模拟是LUCC研究的核心内容之一。以地处湘西北岩溶山区的张家界市永定区为研究对象,针对目前国际上广泛使用的CLUE-S土地利用变化模型,通过在传统Logistic回归模型中引入空间自相关变量,对CLUE-S模型的空间分析模块进行了改进。实验与分析结果表明,改进的空间分析模块拟合优度、拟合精度都有较大的提高。耕地、林地及居民点工矿用地的拟合优度(ROC值)分别从0.784、0.821和0.741提高到0.827、0.875和0.838。在此基础之上,采用改进的CLUE-S模型,模拟和预测了研究地区2005~2020年的土地利用时空变化。研究结果说明对CLUE-S模型空间分析模块的改进在一定意义上是合理的,同时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。