The role of local land-use on the urban heat island effect of Tel Aviv as assessed from satellite remote sensing

Climate change in cities has received much focus in the past few decades. Heat stress in urban areas has an adverse effect on human health and is expected to worsen in the future due to the global warming. Vegetation has been shown to mitigate this effect, but introducing ‘green’ areas into the metropolitan space is a challenging task. We assessed the thermal load in terms of surface temperature in Tel Aviv, the biggest metropolitan area of Israel. The thermal effect of four different urban land uses was estimated. Specifically, we compared the cooling effect of residential areas with high vegetation cover (referred here as ‘green’ residential) to that of small to medium size (2–40 ha) public parks. To this end, we used satellite data of land surface temperature (LST) and the Normalized Difference Vegetation Index (NDVI), as a surrogate for vegetation cover. High-temporal data were combined with high spatial resolutions data to produce 10-year average LST and NDVI maps at high spatial resolution over Tel Aviv. As expected, industrial areas had the highest LST due to lowest ratio of vegetation to free space area (1%), while ‘green’ areas displayed the lowest LST. Green residential and small-medium public parks had comparable thermal loads, with green residential having slightly lower LST (by 0.5 °C). In general, small-medium public parks displayed higher LST than expected. Inefficient use of free spaces for vegetation, i.e., relatively low vegetation cover to free space ratio, was probably the main cause for this. Public parks had a higher local cooling effect, but a less continuous one on the proximate surrounding (30–90 m from the park), probably due to their relative location in the urban fabric. Our results suggest that ‘greening’ areas within the private urban space should be encouraged at the expense of building new small-medium parks in metropolitan areas that lack the sufficient free space for larger parks. The outcome of this study may have key implications for urban planners seeking to mitigate urban heat island effects under the limitation of existing dense urban layout.     

北京野鸭湖湿地资源变化特征

湿地是自然界的生态系统和景观类型,具有巨大的资源潜力和环境功能。长期以来,由于人类活动影响造成的湿地景观巨大变化,不仅仅改变了湿地景观原有的功能,而且对湿地环境产生重要影响。基于RS、GIS技术,通过对北京野鸭湖湿地的Landsat-TM影像和印度IRS影像进行融合处理,得到分辨率高的多光谱图像。结合实地调查,建立解译标志,运用ArcGIS9.0进行矢量化、空间分析和数据统计功能,并统计植被覆盖变化,分析研究1998~2004年野鸭湖湿地资源变化特征。在上述技术路线和研究方法的基础上,总结出该区域的湿地变化特征,最后应用累积效应的原理和方法,对深入研究的科学问题进行了展望,提出一些需要深入探讨的问题。     

Integrated vegetation classification and mapping using remote sensing and GIS techniques

1INTRODUCTIONResearchonglobalenvironmentalchange,especiallyglobalvegetationchange,hasbeenmoreandmoreemphasizedbyscientistsandgovernments.HoWever,theinvestigationofvegetationcoveredinlargeareaneedagreatdealoffundandlaal.Asthesatelliteremotesensingdatahavebeenavailablesinceearly1980s,thesedataarebeingemployedtowardstOtheimprovementofvegetationclassification.NOAA--AVHRRdatahavebeenmoreandmoreusedbyscientistsbecauseOfitsshorttemPOralrefution,largescope,inexpensivecostandbreadwavebands.On…     

蒙古中部地区植被覆盖衰退问题案例研究（英文）

本文选择蒙古中部地区的两个模型多边形对植被多样性进行调查研究。它们都位于干旱、半干旱少雨地区。基于Landsat TM影像,本文研究了多边形区域的NDVI随时间变化的多时相NDVI值制图,得到所选择的具备不同值NDVI区域的全尺度景观特征。这一特征在对耐旱环境组的植被分析中得到了证实。该过程中将近整个实验多边形区域的植被偏离得到了追踪。NDVI的时间分布分析呈现出数值的降低,这说明了在戈壁,稀疏植被存在耐旱趋势。在半干旱气候区域中偏离植被趋势与牧草地的重载负直接相关。     

乡村人口迁出对生态脆弱地区植被覆被的影响——以内蒙古自治区为例

生态脆弱地区的生态环境状况改善和治理一直是各级政府部门和学者关注的焦点问题。过去10余年,中国城镇化进程发展迅速,生态脆弱地区乡村劳动力大量迁出。那么劳动力人口迁出会在多大程度上影响脆弱地区植被覆被状况的变化呢?本研究利用2000-2010年的NDVI数据、气象观测数据和社会经济数据,采用趋势线分析、显著性检验和多元回归分析等方法,对内蒙古地区植被覆被状况的变化进行了分析,并在县级尺度上定量评估了乡村劳动力人口迁移对区域植被覆被状况的影响。结果表明：① 2000-2010年,内蒙古自治区植被覆被总体呈上升趋势,其中超过28%的地区植被覆被状况显著改善,只有约2%的地区存在较强的退化趋势;② 植被覆被显著退化的地区呈条带状分布于内蒙古自治区中部农牧交错带北部边缘;植被覆被显著改善的地区主要位于内蒙古自治区的东南部与西部地区;③ 2000-2010年,农业劳动力对植被覆被状况的影响已经超过了气候等自然因素的作用,农业劳动力迁出对植被覆被状况提高有显著的促进作用。     

Spatio-temporal Patterns of Vegetation Change in Kazakhstan from 1982 to 2015

The Normalized Difference Vegetation Index (NDVI), as a key indicator of vegetation growth, effectively provides information regarding vegetation growth status. Based on the Global Inventory Monitoring and Modeling System (GIMMS) NDVI time series data for Kazakhstan from 1982 to 2015, we analyzed the spatial pattern and changes in the vegetation growth trend. Results indicated that the three main types of vegetation in Kazakhstan are cropland, grassland and shrubland, and these are distributed from north to south. While the regional distribution pattern is obvious, the vegetation index decreased from north to south. The average NDVI values of the three main vegetation types are in the order of cropland > grassland > shrubland. During the period from 1982 to 2015, the NDVI initially increased (1982-1992), then decreased (1993-2007), and then increased again (2008-2015). The areas where NDVI decreased significantly accounted for 24.0% of the total land area. These areas with vegetation degradation are mainly distributed in the northwest junction between cropland and grassland, and in the cropland along the southern border. The proportions of total grassland, cropland and shrubland areas that were degraded are 23.5%, 48.4% and 13.7%, respectively. Areas with improved vegetation, accounting for 11.8% of the total land area, were mainly distributed in the mid-east cropland area, and the junction between cropland and grassland in the mid-east region.     

Explaining NDVI trends in northern Burkina Faso

Many studies have shown a ‘greening of the Sahel’ on the basis of analysis of time series of satellite images and this has shown to be, at least partly, explained by changes in rainfall. In northern Burkina Faso, an area stands out as anomalous in such analysis, since it is characterized by a distinct spatial pattern and strongly dominated by negative trends in Normalized Difference Vegetation Index (NDVI). The aim of the paper is to explain this distinct pattern. When studied over the period 2000–2012, using NDVI data from the MODIS sensor the spatial pattern of NDVI trends indicates that non-climatic factors are involved. By relating NDVI trends to landscape elements and land use change we demonstrate that NDVI trends in the north-western parts of the study area are mostly related to landscape elements, while this is not the case in the south-eastern parts, where rapidly changing land use, including. expansion of irrigation, plays a major role. It is inferred that a process of increased redistribution of fine soil material, water and vegetation from plateaus and slopes to valleys, possibly related to higher grazing pressure, may provide an explanation of the observed pattern of NDVI trends. Further work will focus on testing this hypothesis.     

内蒙古典型草原与荒漠草原NDVI对气象因子的响应

分析了内蒙古典型草原与荒漠草原NDVI的变化,探讨了干旱对NDVI的影响,建立了NDVI与气象因子的回归模型。结果表明:2000-2016年内蒙古典型草原与荒漠草原NDVI呈现波动变化,变异较小。干旱对典型草原区的羊草(Leymus chinensis)群落与大针茅(Stipa grandis)群落NDVI影响显著(P<0.05);与正常年份相比,干旱导致羊草群落与大针茅群落NDVI降低约23%。5-8月降水量和干燥度指数影响内蒙古典型草原羊草群落与大针茅群落NDVI;荒漠草原区羊草+短花针茅(Stipa breviflora)群落与沙生针茅(Stipa plareosa)群落NDVI的主要影响因子分别为年均气温与5-8月平均气温;5-8月降水量和年均气温是影响典型草原和荒漠草原NDVI的重要因子。基于气象因子的NDVI回归模型能够较好地对区域NDVI进行估测。生长季降水是影响典型草原NDVI的关键因素,而气温显著影响荒漠草原NDVI。在未来气候变化的背景下,内蒙古典型草原NDVI对干旱的响应会更加敏感。     

西北地区植被变化对风沙活动的影响分析

基于西北地区1982—2003年NDVI与扬沙日数、沙尘暴日数、大风日数等风沙活动数据,分析了植被变化对风沙活动的影响及其区域差异性。结果表明,NDVI正距平和风沙活动因子的负距平有很好的对应关系。年均NDVI和扬沙日数、沙尘暴日数和大风日数的Kendall相关系数分别为-0.437(99%置信水平)、-0.338(95%置信水平)和-0.251(90%置信水平)。NDVI和各风沙活动因子的相关性随季节发生显著变化。各地貌类型区内,低山-丘陵及洼地区NDVI和风沙活动因子相关最为显著。     

科尔沁沙地不同沙地景观区植被指数对水热因素响应

在全球气候变化背景下,不同尺度下植物对环境条件的响应机制是生态学研究的核心。为了更好理解不同沙地景观区域植被指数(NDVI)对气象水热环境因子的响应机制,以2000-2013年7-9月MODIS遥感影像为数据源,采用3S空间分析技术和通径分析方法,对科尔沁沙地围封保护区、人工造林固沙区和流动沙丘区等3种景观类型区NDVI的变化趋势和影响其变化的同期气象水热因子年降水、关键期降水、关键期最大一次性降水、重要期降水、年均温、关键期均温、关键期最高气温、关键期最低气温等8个因素进行了分析。结果表明:不同景观类型区NDVI整体上呈现增长的态势。降水的影响明显高于气温,且降水主要起正相关作用,气温主要起负相关作用。促进沙地围封保护景观区NDVI增长的气象因子是关键期降水,决策系数最大且为正(0.445);人工造林固沙景观区受到人工造林更新和农业开垦的影响,削弱了水热条件对NDVI的影响,相比较而言,重要期降水影响较大;流动沙丘景观类型区主要受到关键期气温极值的影响,其他因子影响不显著。