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利用遥感生态指数(RSEI)对区域生态变化进行评价,可以快速、高效、客观地获取研究区生态环境变化状况.本研究以两期Landsat数据为数据源,计算研究区绿度、湿度、热度、干度4个生态因子的遥感生态指数,并基于主成分分析法确定其权重,对古尔班通古特沙漠2006—2017年间的生态环境时空格局进行定性和定量评价.结果表明: 湿度和绿度对古尔班通古特沙漠生态环境质量起正面作用,而热度和干度对生态环境质量起负面作用,其中代表绿度指标的归一化植被指数(NDVI)的贡献最大.2006—2017年间,古尔班通古特沙漠的RSEI有所下降,其均值从0.294下降至0.243,降幅达20.1%,研究区的生态环境状况呈现整体变差的趋势.古尔班通古特沙漠中部生态环境较为稳定,东北部植被覆盖密集区及南缘灌溉区生态环境质量变好,沙漠南部及西北部区域生态环境质量变差.  相似文献   
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水资源是一切生物赖以生存和不可替代的基本自然资源,生态需水在维持流域生态系统平衡和生态承载力可持续性方面扮演着极其重要的角色,干旱区内陆河流域尤为突出。以疏勒河流域和其所辖县区为不同尺度区域,利用LandsatTM/ETM+/OLI遥感数据(30 m分辨率),解译该流域近20年5期土地利用数据,同时在收集和整理流域多年水文水资源基础数据的基础上,以流域生态需水为研究主线,运用多学科方法和原理,结合遥感技术、GIS技术,通过现场调查和观测,计算了流域及其所辖县区近20年生态承载力和天然植被生态需水量。结果表明:近20年来,伴随流域生态承载力的增加,生态需水量也呈增加趋势,两者呈非常明显的正相关关系,相关系数达0.6076;县域尺度上,生态需水与生态承载力正相关关系也较高,其中林、草地的生态需水与生态承载力拟合优度R~2分别达0.8519、0.7235,说明林、草地生态承载力的变化对生态需水变化的解释能力更强,二者之间的关系更为紧密;基于空间热点分析,该流域生态承载力和生态需水的热点和冷点区域均呈现相似的空间格局,说明二者之间在空间尺度上也呈正相关关系。研究结论可为疏勒河流域生态水资源量的科学配置和调控提供重要的决策依据。  相似文献   
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Few regions have been more severely impacted by climate change in the USA than the Desert Southwest. Here, we use ecological genomics to assess the potential for adaptation to rising global temperatures in a widespread songbird, the willow flycatcher (Empidonax traillii), and find the endangered desert southwestern subspecies (E. t. extimus) most vulnerable to future climate change. Highly significant correlations between present abundance and estimates of genomic vulnerability – the mismatch between current and predicted future genotype–environment relationships – indicate small, fragmented populations of the southwestern willow flycatcher will have to adapt most to keep pace with climate change. Links between climate‐associated genotypes and genes important to thermal tolerance in birds provide a potential mechanism for adaptation to temperature extremes. Our results demonstrate that the incorporation of genotype–environment relationships into landscape‐scale models of climate vulnerability can facilitate more precise predictions of climate impacts and help guide conservation in threatened and endangered groups.  相似文献   
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Although a number of recent studies have demonstrated biotic homogenization, these have mainly focused on larger spatial scales. Homogenizing effects are equally important at finer resolutions, e.g. through increasing similarity between habitats, which may result in a simplification of ecosystem structure and function. One major cause of homogenization is the expanding ranges of alien species, although it is not clear whether they are inherently homogenizing at smaller scales. We therefore assessed whether the alien flora is less complex across habitats than the resident native flora of Mediterranean Islands. From a regional data base, we examined floristic lists for between‐habitat taxonomic and functional similarity, and within‐habitat functional diversity, using resampled data sets to control for sample size biases. Aliens and natives showed equivalent complexity in most respects. At the taxonomic level, between‐island and between‐habitat similarities were almost identical, and when ecosystem function was measured by a functional group classification system, this was also true of between‐habitat similarities and within‐habitat diversities. When ecosystem function was measured using Grime's CSR classification, aliens were found to be more functionally homogenous between‐habitats and less functionally diverse within habitats. However, since the CSR profiles of aliens and natives differed, simplification is not inevitable due to ecological segregation of the two floras (aliens tend to be recruited to disturbed habitats rather than displacing natives). One deficiency is a lack of large scale species abundance data. A simple simulation exercise indicated that this is likely to lead to substantial overestimation of true levels of similarity, although would only influence the comparison between aliens and natives if they have different abundance distribution curves. The results indicate that alien floras are not intrinsically more simple than natives, but a higher proportion of competitive strategists among aliens may still cause small‐scale homogenization as these include many strong competitors that are likely to dominate communities.  相似文献   
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To assess natural attenuation and the efficiency of remediation actions after more than two years a large accident with gasoline spill contaminated a wetland in a tropical region, an Ecological Risk Assessment based on the Dutch Triad was applied. In total, eight surface water-sampling points were distributed randomly in the affected area and on reference area upstream the contaminated site, with similar ecological characteristics. Risks based on chemical, ecotoxicological, and ecological lines of evidence (LoE) were calculated to integrate the environmental risk indexes. The chemical risk was derived from toxic pressure coefficients based on the total BTEX and naphthalene concentrations. Ecotoxicological LoE based on acute toxicity with Daphnia similis and Aliivibrio fischeri bioassays and chronic toxicity with Desmodesmus subspicatus bioassay contributed to raise uncertainty due to low sensitivity of acute assays. Genotoxicity and endocrine disruption biomarkers of Oreochromis niloticus were used to calculate the Biomarker Stress Index (BSI) assumed as Ecological Risk Index. The integration of the Chemical Risk Index with BSI to estimate the Biological Vulnerability Index allowed a meaningful analysis of the threats to the aquatic ecosystem, thereby supporting managers and decision-makers.  相似文献   
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城市森林景观格局与过程研究进展   总被引:14,自引:1,他引:13  
大规模的城市化进程,改变了城市以及周边区域的景观格局,显著影响着城市森林生态系统的结构、过程与功能.景观尺度上的城市森林景观格局与生态过程研究已经成为当前城市森林学的研究热点.在阐明城市森林及其景观格局与过程概念的基础上,综述了国内外城市森林景观格局与过程的研究内容、研究方法的进展情况,指出了以下几个方面有望成为今后城市森林景观研究的发展方向:景观尺度上的城市森林系统能流、物质循环等生态学过程研究;城市森林景观格局演变的社会驱动力研究;基于生态服务功能的城市森林规划研究;半都市化地区的森林景观格局与过程研究;基于空间显式景观模型的城市森林景观格局与过程模块开发.  相似文献   
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宁夏资源环境绩效及其变动态势   总被引:3,自引:1,他引:2  
提高资源环境绩效是我国生态脆弱敏感区进行生物修复的核心和关键.利用生态环境状况评价技术规范和资源环境绩效指数(REPI)对我国西部生态环境脆弱区的宁夏回族自治区资源环境绩效进行了系统分析.结果表明:尽管宁夏的资源环境绩效指数水平从2000年的38.7上升为2007年的66.9,年递增8.13%,但远低于全国平均水平和(西藏除外)3个少数民族自治区水平.资源环境综合绩效水平在全国的第30位徘徊.其中建设用地绩效指数和固定资产绩效指数提升明显,COD排放绩效指数呈现"N"型剧烈变动态势;SO_2排放绩效指数、能源绩效指数、工业固体废弃物排放绩效指数、用水绩效指数变动不明显.宁夏面临生态环境的整体不稳定性和对外力干预敏感性的双重压力,资源消耗和污染物排放的下降态势并不稳定.同时,根据近8a变动态势推断,未来15~20a宁夏资源环境综合绩效的提升空间巨大.实施"CIRCLE"(即压缩城市发展(C)、个人行动(I)、减少潜在废弃物量(R)、碳减排战略(C)、土地管理(L)和提高能效(E))等综合发展策略,通过轻量化、绿色化、生态化的互利耦合提升综合竞争力,宁夏完全有能力到2015年步入我国西部资源环境绩效中等水平地区行列.  相似文献   
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Antigenic diversity in pathogenic microbes can be a result of at least three different processes: diversifying selection by acquired immunity, host–pathogen coevolution and/or host specialization. Here, we investigate whether host specialization drives diversity at ospC (which encodes an immunodominant surface protein) in the tick‐transmitted bacterium Borrelia afzelii. We determined prevalence and infection intensity of ospC strains in naturally infected wild mammals (rodents and shrews) by 454 amplicon sequencing in combination with qPCR. Neither prevalence nor infection intensity of specific ospC strains varied in a species‐specific manner (i.e. there were no significant ospC × host species interactions). Rankings of ospC prevalences were strongly positively correlated across host species. Rankings of ospC infection intensities were correlated more weakly, but only in one case significantly < 1. ospC prevalences in the studied mammals were similar to those in ticks sampled at the study site, indicating that we did not miss any mammal species that are important hosts for specific ospC strains. Based on this, we conclude that there is at best limited host specialization in B. afzelii and that other processes are likely the main drivers of ospC diversity.  相似文献   
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