Linked and Independent African American Migration from Los Angeles

Empirical evidence of environmental performance of urban areas designed according to the principles of sustainable urbanism is limited. Using the case study of Civano, a planned development that was designed and marketed as a sustainable community in Tucson, Arizona, we quantify fine-scale differences in urban form and delivery of ecosystem services. We found that the urban design of the first phase of development translated to the lowest surface temperatures and highest albedo and vegetative density. The first and second phases of the development greatly reduced potable water consumption through the addition of nonpotable resources; however, the second phase had higher temperatures and less dense vegetation than even the conventional development. Our results show modest improvements in environmental performance through sustainable urbanism and suggest further refinement in fine-scale spatial analysis of the role of urban design in the provisioning of services.     

Identification of geomorphic process units in Kärkevagge, northern Sweden, by remote sensing and digital terrain analysis

Sediment transport processes in the Kärkevagge are investigated concerning their spatial and temporal characteristics due to long–term monitoring. Within this study remote sensing techniques and GIS modelling in connection with geomorphic mapping are applied for identification and characterization of geomorphic process units. Relationships between geomorphometric parameters and slope processes like solifluction, talus creep and rockfall have been analysed. Multitemporal Landsat–TM5 scenes are used as source for landcover characteristics (Normalized Difference Vegetation Index) after preprocessing involving orthorectification and topographic normalization in order to remove possible terrain–induced effects. Additionally, a digital elevation model with a resolution of 20 m for the Kärkevagge catchment is developed and parameters like slope gradient, slope aspect and profile curvature are extracted as input for the analysis of the sediment transport system. The combination of landcover information, geomorphometrical and topological features allows the definition of areas for single process activities. They show specific sediment displacement characteristics depending on material conditions, topological and geometrical features. Geomorphic process units, which show a homogenous composition, are extracted from these available layers.     

Identification of geomorphic process units in Kärkevagge, northern Sweden, by remote sensing and digital terrain analysis

Sediment transport processes in the Kärkevagge are investigated concerning their spatial and temporal characteristics due to long–term monitoring. Within this study remote sensing techniques and GIS modelling in connection with geomorphic mapping are applied for identification and characterization of geomorphic process units. Relationships between geomorphometric parameters and slope processes like solifluction, talus creep and rockfall have been analysed. Multitemporal Landsat–TM5 scenes are used as source for landcover characteristics (Normalized Difference Vegetation Index) after preprocessing involving orthorectification and topographic normalization in order to remove possible terrain–induced effects. Additionally, a digital elevation model with a resolution of 20 m for the Kärkevagge catchment is developed and parameters like slope gradient, slope aspect and profile curvature are extracted as input for the analysis of the sediment transport system. The combination of landcover information, geomorphometrical and topological features allows the definition of areas for single process activities. They show specific sediment displacement characteristics depending on material conditions, topological and geometrical features. Geomorphic process units, which show a homogenous composition, are extracted from these available layers.     

Variability in soil redistribution in the northern Chihuahuan Desert based on Cesium measurements

A hypothesis for understanding the stability of northern Chihuahuan Desert landscapes is that the distribution of soil resources changes from spatially homogeneous in arid grasslands to spatially heterogeneous in invading shrublands. Since radioactive fallout ¹³⁷Cesium (¹³⁷Cs) was deposited uniformly across the landscape during the 1950s and 1960s and was quickly adsorbed to soil particles, any redistribution of ¹³⁷Cs across the landscape would be due to soil redistribution or instability at either plant-interspaces or on a landscape scale. The concentration of ¹³⁷Cs in soils collected from different vegetation communities (black grama grass, tarbush, tobosa grass, and mesquite) at the USDA-ARS Jornada Experimental Range in the Northern Chihuahuan Desert in New Mexico was determined. At the black grama grass and tobosa grass sites, ¹³⁷Cs was uniformly distributed at the plant interspace scale. At the mesquite sites, ¹³⁷Cs was concentrated in the dune area under mesquite shrubs with little to no ¹³⁷Cs in the interdune areas. ¹³⁷Cs data support the hypothesis that significant soil redistribution has occurred at dune sites created by invading mesquite. In the arid grassland-shrub sites with black grama grass, tobosa grass, and tarbush the ¹³⁷Cs data support the hypothesis of spatially homogeneous distribution of soil resources. High concentrations of ¹³⁷Cs in the biological soil crusts (0–5 mm) at the tarbush sites indicate that biological soil crusts can contribute to the stability of these sites.     

Modeling the effects of historical vegetation change on near-surface atmosphere in the northern Chihuahuan Desert

Our goal was to evaluate effects of broad-scale changes in vegetation from grasslands to shrublands over the past 150 years on near-surface atmosphere over the Jornada Experimental Range in the northern Chihuahuan Desert, using a regional climate model. Simulations were conducted using 1858 and 1998 vegetation maps, and data collected in the field. Overall, the vegetation shift led to small changes in sensible heat (SH) and an increase in latent heat (LH). The impacts of shrub encroachment depended on shrubland type: conversion from grass to mesquite cools the near-surface atmosphere and from grass to creosotebush warms it. Higher albedo of mesquite relative to grasses reduced available energy, which was dissipated mainly as LH due to the deeper root system in mesquite. In creosotebush-dominated areas, a decrease in albedo, an increase in roughness length and displacement height contributed to the SH increase and warmer temperatures. Sensitivity simulations showed that an increase in soil moisture content enhanced shrub LH and a reduction in mesquite cover enhanced the temperature differences. The observed shift in vegetation led to complex interactions between land and surface fluxes, demonstrating that vegetation itself is a weather and climate variable as it significantly influences temperature and humidity.     

近35 a来新疆干旱区湖泊变化及原因分析

应用“3S”技术,以流域为单元,对新疆干旱区1975-2010年近35 a来湖泊的变化进行了研究。研究结果表明：湖泊总体呈数量多、规模小的特点,以天然湖泊为主,湖泊分布面积最大的流域为准噶尔内流区、分布数量最多的流域为塔里木内流区;35 a来湖泊的变化呈1975-2000年数量与面积增大、2000-2010年数量与面积减少的特征;天然湖泊与人工湖泊变化差异显著,天然湖泊数量与面积均呈先增加后减少的变化特征,而人工湖泊数量及面积均呈持续增加的变化特征;1975-2000年各流域湖泊面积均增大,2000-2010年除伊犁河内流区外,各流域湖泊面积均大幅度减小;影响新疆干旱区湖泊变化的主要气候因素是降水与气温,人类活动是流域间湖泊变化幅度与变化趋势差异的主要影响因素,也是影响天然湖泊与人工湖泊变化趋势差异的主要原因。     

Plant productivity, predation, and the abundance of black-tailed jackrabbits in the Chihuahuan Desert of Mexico

The abundance of black-tailed jackrabbits (Lepus californicus) can fluctuate dramatically. We used data from the Chihuahuan Desert to test the relative strength of top-down (predation) or bottom-up (food availability) limiting forces. Predictions for the top-down hypothesis were, 1) a positive relationship between coyote (Canis latrans) and jackrabbit abundance (numerical response) and 2) a positive relationship between percent occurrence of jackrabbits in coyote scats and jackrabbit abundance (functional response). Predictions for the bottom-up hypothesis were, 1) plant productivity is directly related to precipitation, 2) jackrabbit abundance is positively related to precipitation and plant productivity, and 3) changes in abundance of jackrabbits over the reproductive season will be directly related to precipitation and plant productivity. We found a limited numerical response but no functional response of coyotes to jackrabbit abundance. Forb productivity was significantly related to annual precipitation levels (r² = 0.69, p = 0.002). Grass productivity was related to annual precipitation (r² = 0.34, p = 0.028). Jackrabbit abundance (r² = 0.38, p = 0.002) and changes in abundance (r² = 0.73, p < 0.001) were significantly related to precipitation and forb and grass productivity. We conclude that precipitation levels and plant productivity affect jackrabbit abundance more than predation levels.     

Stable isotopes and soil-geomorphology as indicators of Holocene climate change, northern Chihuahuan Desert

Coeval δ¹³C shifts recorded in buried soils at both piedmont slope and basin floor sites in the northern Chihuahuan Desert indicate a major shift from C₄grasses to C₃desert-scrub between 7 and 9 ka. The age assignments are based on stratigraphic correlations to charcoal dates and carbon-14 dates of carbonate. This shift is synchronous with a period of cooling in the North Atlantic that may have triggered a period of drought in the south-western United States. Coinciding with this vegetation change, geomorphic evidence in Rio Grande, piedmont, and basin floor eolian environments indicates a major period of erosion. Subsequent gradual enrichment of pedogenic carbonateδ¹³ C values in younger deposits suggests that C₄grasses rebounded in the late Holocene (approximately 4 ka), which is consistent with other evidence of increased moisture regionally. A period of less severe aridity at approximately 2·2 ka is indicated by erosion and subsequent deposition along the alluvial fans and within the basin, and correlates with depleted pedogenic carbonate δ¹³C values suggesting a decrease in C₄grasses. Isotope and packrat midden records should be used together to infer past environmental conditions at different elevations.     

基于GIS的伊犁河流域生态环境质量评价与动态分析

生态环境质量评价是一项综合性、系统性研究工作,是合理开发利用资源、制定经济社会可持续发展规划和生态环境建设与保护对策的前提和基础。借助GIS技术,以县级行政区划为单元,利用2002和2004年遥感监测数据,运用综合指数评价法,从生物丰度、植被盖度、水网密度、土地退化和污染负荷5个方面,对伊犁河流域8县1市的环境质量现状进行了评价,结果表明:各县级行政区生态环境质量总体较为均衡,均处于一般等级水平,其中流域上游的新源县、巩留县和特克斯县相对较好。在此基础上探讨了生态环境质量综合评价指标体系在干旱区的适用性,比较分析2年期间不同生态环境质量等级的土地覆盖变化,数据表明伊犁河流域生态环境质量呈现"局部有所改善、总体缓慢退化"的趋势,并分析了研究区生态环境质量变化的内在原因。     

基于遥感和GIS技术的荒漠化动态分析——以宁夏盐池为例

荒漠化是当今全球和中国最为严重的环境与社会经济问题之一,它的危害已深入到自然与社会经济的各个方面。选取荒漠化问题突出的宁夏盐池县作为研究区,通过3期遥感TM影像(1986年、1996年、2000年),运用GIS的分析手段,综合土地利用图、地形图和其他资料形成盐池县3期荒漠化现状图及两阶段动态图。盐池荒漠化土地类型的结构变化表明,荒漠化受非荒漠化类型土地限制,其面积有所减小,但程度在加重。荒漠化发展的原因是自然因素与人为因素共同作用的结果。     

2000-2012年中国北方海岸线时空变化分析

利用遥感和GIS 技术获取了中国北方“三省一市”2000 年、2005 年、2008 年、2010年、2011 年与2012 年共6 期大陆海岸线的时空分布情况;采用网格法计算了各个时期海岸线的分形维数;分析了海岸线时空变化特征、海岸线长度变化与分形维数变化之间的关系,以及海岸线动态变化的原因。2000-2012 年,研究区海岸线长度持续增加,总共增加了637.95km,年均增加53.16 km。从区域上看,以天津市与河北省所在的渤海湾区域海岸线变化最强烈;从时间过程上看,2008 年后海岸线长度进入快速增长时期,其中2010-2011 年是海岸线长度变化最剧烈的时期,变化强度为2.49%。2000-2012 年研究区海岸线的分形维数不断增大,其中渤海湾区域海岸线分形维数变化最剧烈;历史海岸线的长度与分形维数之间存在较好的线性关系,相关系数为0.9962;通过对大量海岸线动态引起的整体海岸线长度变化与分形维数变化的统计分析研究表明,在大多数情况下,局部海岸线长度增大(或缩减) 会导致整体海岸线分形维数增大(或减小),并且呈正比例变化。从2000-2012 年各时段海岸线动态对应的各类沿海工程的面积汇总情况来看,港口建设、渔业设施建设以及盐场建设分别占前三位,人类工程建设是中国北方海岸线变化最主要原因;与人类活动影响相比,自然变化如河口淤积与侵蚀对海岸线影响比较小。     

Estimation of Summer Rainfall over an Arid Area using AMSR-E Measurements: A Case Study in Xinjiang, China

Rainfall estimate in arid region using passive microwave remote sensing techniques has been a complex issue for some time.The main reason for this difficulty is that the high and variable emissivity of land surfaces greatly aggravates the complexity of the signatures from the rain cloud.The Xinjiang area,located in the northwest of China,holds all the typical characteristics of arid climate.A rainfall algorithm has been developed for this region by using the Advanced Microwave Scanning Radiometer for Earth Observing System(AMSR-E) measurements.The algorithm attempts to use all 12 chan-nels on the AMSR-E instrument and a two-step method calibrated over 11 days of hourly rain-gauge data.First,Stepwise Discriminant Analysis(SDA) used to optimally estimate rain pixels based on all 12 channels,although only three channels were found to be necessary.Next,a rain predicator scattering index was used to estimate rain rates.A linear relationship between the rain rates and the scattering index above the threshold of 3.0K was constructed with a simple approximately linear function.The estimated rain rates were compared with the rain-gauge data used to calibrate the method,and a good relationship was found with a root-mean-square error of 2.1mm/h.The numerical calculations and comparisons show that the algorithm works well in the Xinjiang area.     

A landscape management analysis framework and its preliminary application in Ejina Oasis,Northwest China

The implementation of integrated landscape management to support local and regional human well-being is crucial in arid regions,but its application to date is very limited.Although analytical frameworks have been established to maximize ecosystem services via trade-offs between different landscape configurations,consumption factors such as water resources are rarely and weakly considered in such frameworks.In this paper,an improved integrated landscape-management analysis framework,called the Consumption-integrated Landscape Management to Ecosystem Service(CLMES),is proposed.In this framework,consumption factors are integrated at the same level as ecosystem services.The improved analytical framework is then used to assess and optimize landscape design in the Ejina Oasis,an extremely arid region in western China.Three landscape conditions(past,current,and future)are evaluated,based on the CLMES.Our results indicate that the Heihe River water-allocation program effectively promoted ecosystem services in the Ejina Oasis from 2000 to 2011.However,the excessive expansion of cropland led to a slight decline in habitat quality.An optimized landscape configuration and policy suggestions are proposed,which may be beneficial to the improvement of total water-use efficiency,oasis stability,and resilience of the ecological?social system in the Ejina Oasis.     

在GIS支持下的东南山区土壤景观监测与制图

本研究就土壤景观的监测方法、制图技术进行探讨，提出了以景观生态学分析和地物隶属关系分析为主的东南山区土壤景观制图技术。利用GIS和RS技术，通过图形叠加、图形-影象叠架而生成的双因素、三因素叠加图，不但反映了土壤景观变化，而且量化了土壤景观因素之间的关系。如1997年与1985年相比，中海拔地形中多样性指数下降，土壤景观结构的有序性增强；但低海拔和最高海拔的地形中多样性指标上升，土壤景观结构的有序性变差，同时优势度指数也有所下降。     

Coyote diets in the Chihuahuan Desert, more evidence for optimal foraging

With 7 years data on coyote prey use and availability, we tested three predictions based on optimal foraging: (1) the proportion eaten of the most profitable item is constant regardless of availability, (2) under a constant density of higher ranked prey, there is no relationship between the proportion eaten of low profitability items and their density, (3) the ratio of number consumed to availability for the highest ranking prey item should be negatively related to availability. We tested these predictions with regression analyses. We found no significant linear relationship between lagomorph availability and use. There was no significant linear relationship between percent frequency of occurrence of rodents nor arthropods and their respective availabilities for two levels of availability of lagomorphs. We found a significant negative relationship between number consumed/number available to availability for lagomorphs but not for rodents nor arthropods. The results supported the three predictions and we concluded that coyotes are foraging optimally.     

策勒河流域荒漠类型特征研究

策勒河流域荒漠类型多样,在干旱区具有典型代表性。基于Landsat5的TM遥感影像数据、数字高程模型（DEM）数据,利用GIS技术,结合野外调查、样品采集及实验室粒度、有机质、盐分分析,对策勒河流域荒漠类型分类,并编制荒漠类型分布图。据地貌类型、物质组成、植被盖度等指标将流域内荒漠分为2个一级类,7个二级类,14个三级类,建立策勒河流域荒漠类型分类系统。流域荒漠自下游向上游具有依次是沙漠、砾漠、岩漠、土漠和寒漠空间分布的规律;荒漠总面积2 416.76 km²,占流域总面积的70.45%,砾漠占荒漠总面积的45.52%,为最大一类,泥漠所占比重最小。可为流域环境保护、荒漠化防治提供依据,为其他干旱区荒漠类型研究提供参考。     

Recruiting mechanisms of Cylindropuntia leptocaulis (Cactaceae) in the Southern Chihuahuan Desert

Sexual reproduction and vegetative propagation require the establishment of morphologically diverse reproductive structures (seedlings and stem segments). This study assesses both types of Cylindropuntia leptocaulis recruitment in two microenvironments protected from herbivory (in open space and under the canopy of Larrea tridentata) and with two soil types (collected below L. tridentata canopy and from open space).An observational study revealed that sexual establishment was very limited (only 8 juveniles/ha were found), while clonal establishment was more frequent (59 juveniles/ha); both types of propagule were found only under shrub canopy.Field experiments showed that, as in other Cylindropuntia species but contrasting with findings for Opuntia species, seeds germinated and seedlings survived under nurse plants as well as in open space, but they grew faster in the former environment. Faster growth under canopy shade provides better chances of successful recruitment to later life-cycle stages. Stem segments never established in open space, requiring the shade of nurse plants. This may be due to physiological constraints imposed by their small volume. In synthesis, the results indicate that clonal propagation is the most important recruitment mechanism in C. leptocaulis populations, and that it takes places under shrub canopy.     

基于ASTER图像的干旱区土壤盐碱化遥感应用研究

土壤盐碱化是干旱地区常见的一种土地退化现象。为了对土壤盐碱化程度进行快速的评估,采用ASTER遥感数据敏感波段组合结合光谱角度制图（SAM）的方法进行了探索性的研究。研究从分析干旱区盐碱地表光谱特征的角度出发,采用图像像元纯度指数分析（PPI）方法提取不同盐碱化水平的地表特征纯像元,结合实地测量光谱数据和采样分析数据确定纯像元的物理意义,并应用光谱角度制图方法进行了土壤盐碱化程度分级制图。经检验,总体分类精度达到79．1％。这种方法对常规数据的依赖性较小,提供了一种适合盐碱化快速定量评估的有效途径。     

“三北”防护林建设以来河西走廊林地变化的遥感监测

为了对中国\!三北\"防护林工程重点建设区河西走廊的防风固沙林工程建设成效进行客观评估,选取4期Landsat MSS、TM/ETM数据,在GIS技术支持下对1978-2007年期间面状林地的动态进行遥感监测。监测结果表明,整个研究区林地面积呈先下降后上升趋势,表现为1978-1990年林地面积明显减少,1990-2000年林地面积大幅度上升,2000-2007年林地呈缓慢上升状态;在不同空间范围内,山区各县林地变化较为缓和,平原区各县林地变化较为明显。在此基础上,分析不同林地变化特征,得出人为因素是本地区林地变化的主要原因。     

Scale Dependencies of Vegetation and Topography in a Mountainous Environment of Montana

This research examines the effects of spatial scale on estimating the relationship between vegetation biomass and topography within a portion of Glacier National Park, Montana. The Reflectance/Absorptance vegetation index, developed from processed Landsat Thematic Mapper digital data, is related to three topographic variables obtained through processed Digital Elevation Models: elevation, slope angle, and slope aspect. R² values between the vegetation index and the topographic variables are obtained from regression analyses at a series of aggregated spatial scales. The effective range of spatial scales within which the two sets of variables are spatially dependent and the degree of the spatial dependencies are characterized through semivariance and fractal analyses.