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851.
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853.
北京入境旅游流西向扩散与省域经济联系研究——以西部三大典型区为例 总被引:1,自引:0,他引:1
北京是我国经济、政治和文化中心,也是我国最重要的入境口岸之一。入京旅游流西向的扩散转移对省域之间旅游经济联系强度具有极大的直接促进作用,转移态是反映旅游流流向和流量的重要指标。在对我国西部三大典型旅游区界定的基础上,利用转移态指数模型和旅游经济联系强度模型对入京旅游流向西转移态及其与西部三大典型旅游区的经济联系强度进行了相关性分析,得出入京旅游流西向转移态对西部典型区经济的影响程度为:成渝泛西安云贵,在此基础上分析了原因,并对西部三大典型旅游区如何更好地吸引北京入境旅游"二手客源",以促进旅游业更快发展提出了相应对策与建议。 相似文献
854.
乡村旅游在实践中正从边缘化向系列化发展。沂蒙山区是全国水土流失重点治理区,针对沂蒙山区乡村旅游资源状况,分析了沂蒙山区发展乡村旅游的市场条件,认为生态脆弱区发展乡村旅游应遵循经济多元复合化发展与内源发展的原则,建构纵向深化与横向附加开发模式,具体提出乡村旅游开发途径,即旅游内容特色化、耦合化,旅游服务网络化、规范化的深化途径与附加旅游教育和旅游养生内容等途径。 相似文献
855.
856.
基于GIS的县域经济差异与协调发展研究——以陕北地区为例 总被引:1,自引:0,他引:1
改革开放以来,陕北地区经济有了突飞猛进的发展,尤其是矿产资源的开发创造了巨大的经济效益。但近几年来,县域经济发展水平的空间差异逐渐扩大,已成为制约该区域经济发展的一大障碍。选取了人均GDP、地均GDP、人均地方财政收入、人均社会消费品零售总额、城镇化水平、在岗职工平均工资和农民人均纯收入7项指标,采用ArcGIS的IDW法模拟和分析了陕北地区经济空间格局,再采用量图分析法将陕北地区25个县级行政区分为先进、中等和落后3种类型,从县域的角度进一步分析经济水平的空间差异,最后对缩小县域经济空间差异和实现县域经济协调发展提出几点建议。 相似文献
857.
Justin M. McGrath 《Environmental pollution (Barking, Essex : 1987)》2010,158(4):1023-1028
Early spring leaf out is important to the success of deciduous trees competing for light and space in dense forest plantation canopies. In this study, we investigated spring leaf flush and how long-term growth at elevated carbon dioxide concentration ([CO2]) and elevated ozone concentration ([O3]) altered leaf area index development in a closed Populus tremuloides (aspen) canopy. This work was done at the Aspen FACE experiment where aspen clones have been grown since 1997 in conditions simulating the [CO2] and [O3] predicted for ∼2050. The responses of two clones were compared during the first month of spring leaf out when CO2 fumigation had begun, but O3 fumigation had not. Trees in elevated [CO2] plots showed a stimulation of leaf area index (36%), while trees in elevated [O3] plots had lower leaf area index (−20%). While individual leaf area was not significantly affected by elevated [CO2], the photosynthetic operating efficiency of aspen leaves was significantly improved (51%). There were no significant differences in the way that the two aspen clones responded to elevated [CO2]; however, the two clones responded differently to long-term growth at elevated [O3]. The O3-sensitive clone, 42E, had reduced individual leaf area when grown at elevated [O3] (−32%), while the tolerant clone, 216, had larger mature leaf area at elevated [O3] (46%). These results indicate a clear difference between the two clones in their long-term response to elevated [O3], which could affect competition between the clones, and result in altered genotypic composition in future atmospheric conditions. 相似文献
858.
Frederik De Laender K. Soetaert 《Environmental pollution (Barking, Essex : 1987)》2010,158(5):1775-1782
The majority of ecotoxicological enclosure experiments monitor species abundances at different chemical concentrations. Here, we present a new modelling approach that estimates changes in food web flows from such data and show that population- and food web level effects are revealed that are not apparent from abundance data alone. For the case of cypermethrin in freshwater enclosures, photosynthesis and excretion (d−1) of phytoplankton at 3.643 μg L−1 cypermethrin were 30% lower and 100% higher than in the control, respectively. The ingestion rate of mesozooplankton (d−1) was 6 times higher in the treated enclosures than in the control as food concentration increased with insecticide exposure. With increasing cypermethrin concentrations, nanoflagellates progressively relied on phytoplankton as their main food source, which rendered the food web less stable. We conclude that this tool has excellent potential to analyse the wealth of enclosure data as it only needs species abundance and general constraints. 相似文献
859.
Scott M. Weir 《Environmental pollution (Barking, Essex : 1987)》2010,158(12):3596-3606
A large data gap for reptile ecotoxicology still persists; therefore, ecological risk assessments of reptiles usually incorporate the use of surrogate species. This necessitates that (1) the surrogate is at least as sensitive as the target taxon and/or (2) exposures to the surrogate are greater than that of the target taxon. We evaluated these assumptions for the use of birds as surrogates for reptiles. Based on a survey of the literature, birds were more sensitive than reptiles in less than 1/4 of the chemicals investigated. Dietary and dermal exposure modeling indicated that exposure to reptiles was relatively high, particularly when the dermal route was considered. We conclude that caution is warranted in the use of avian receptors as surrogates for reptiles in ecological risk assessment and emphasize the need to better understand the magnitude and mechanism of contaminant exposure in reptiles to improve exposure and risk estimation. 相似文献
860.
我国火电厂脱硫脱硝行业2009年发展综述 总被引:3,自引:0,他引:3
中国环境保护产业协会锅炉炉窑脱硫除尘委员会 《中国环保产业》2010,(6):17-20
介绍了2009年我国火电厂脱硫脱硝行业发展概况,分析了行业存在的主要问题,提出了对策及建议,并对行业发展进行了展望。 相似文献