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481.
新原高速公路雁门关隧道出口段滑坡勘察及治理   总被引:3,自引:0,他引:3  
本文对水沟滑坡的形成及滑动机理进行了分析,对滑坡的稳定性进行了计算,得出不同状态下滑坡体的稳定系数及滑坡推力,并根据滑坡体与设计路线工程的关系,提出了在坡体中下部结合桥墩设置抗滑桩、坡体内及周界外设置截排水沟、坡面填坑埋缝的综合治理方案。  相似文献   
482.
Between April 1992 and March 1993,intersexual plasticity in aspects of the biology of the mudskipper,Periophthalmus barbarus was studied.Sec was differentiated on the basis of the genital papillae,it was broader in females than males.Sexually active females were slightly heavier than similarly-sized males.Sex ratio was strongly female-biased.Length-weight relationship of the sexes was isometric.There was no significant difference in the feeding intensity of both sexes;uniformity was also apparent in diet breadth.There was no named sex-based difference in hepatosometic index but condition index was higher in males than females.the uniformity in intersexual plasticity of P.barbarus is consequent upon homogeneity of the mangrove ecosystem,which can only be altered anthropogenically.  相似文献   
483.
我国西部水资源供需关系地区性差异变化研究   总被引:8,自引:1,他引:8  
利用地理信息系统技术,对我国西部12个省(市、区)按流域进行了划分,结合1980年和1990年水文资料,比较了我国西部各流域两个时段可供水量、需水量、缺水量和缺水率变化,系统分析了西部水资源供需关系变化的地区性差异及其原因,并预测了未来我国西部缺水情况,这些研究为我国西部大开发战略的实施提供了基础性依据。  相似文献   
484.
分析了中国部分自然保护区面积与生物物种(动物和植物)之间的关系;其次讨论了动物与植物以及动物与动物物种数量间的关系.结果表明,我国部分自然保护区的面积多数偏小,鸟类、哺乳类、种子植物、爬行类、昆虫和两栖类等与其面积的相关关系依次减弱;其植物种数与鸟类种数的作用影响最大、关系最密切;两栖类与各类动物之间以及鸟类与各类动物之间的物种数目呈显著的相关关系;两栖类与昆虫类为负作用影响;鸟类与两栖类和爬行类以及哺乳类与两栖类为最大的正作用影响.  相似文献   
485.
论灾害行为   总被引:6,自引:0,他引:6  
郭强 《灾害学》1993,8(1):23-27
本文从行为科学的知识出发,探讨了灾害行为及其特征;研究了人与灾害关系的行为特点。  相似文献   
486.
Abstract: Identification of priority areas is a fundamental goal in conservation biology. Because of a lack of detailed information about species distributions, conservation targets in the Zhoushan Archipelago (China) were established on the basis of a species–area–habitat relationship (choros model) combined with an environmental cluster analysis (ECA). An environmental‐distinctness index was introduced to rank areas in the dendrogram obtained with the ECA. To reduce the effects of spatial autocorrelation, the ECA was performed considering spatial constraints. To test the validity of the proposed index, a principal component analysis–based environmental diversity approach was also performed. The priority set of islands obtained from the spatially constrained cluster analysis coupled with the environmental‐distinctness index had high congruence with that from the traditional environmental‐diversity approach. Nevertheless, the environmental‐distinctness index offered the advantage of giving hotspot rankings that could be readily integrated with those obtained from the choros model. Although the Wilcoxon matched‐pairs test showed no significant difference among the rankings from constrained and unconstrained clustering process, as indicated by cophenetic correlation, spatially constrained cluster analysis performed better than the unconstrained cluster analysis, which suggests the importance of incorporating spatial autocorrelation into ECA. Overall, the integration of the choros model and the ECA showed that the islands Liuheng, Mayi, Zhoushan, Fodu, and Huaniao may be good candidates on which to focus future efforts to conserve regional biodiversity. The 4 types of priority areas, generated from the combination of the 2 approaches, were explained in descending order on the basis of their conservation importance: hotspots with distinct environmental conditions, hotspots with general environmental conditions, areas that are not hotspots with distinct environmental conditions, and areas that are not hotspots with general environmental conditions.  相似文献   
487.
Abstract:  Optimization of resource use is necessary for efficient conservation planning. Many reserve-selection algorithms aim to identify representative but inexpensive networks, which may lead to selecting small sites due to their lower costs and collectively higher species richness. Nevertheless, larger sites would be preferable regarding species' long-term persistence. An area-based refinement can be used to overcome this problem. We used a reserve-planning framework in which continuous benefit functions valued representation (numbers of populations), and differential species weights were based on a species' local rarity and threatened status. We introduced a refinement based on the species-area relationship that provides relatively higher values for larger sites. We applied the proposed method to rich fen vegetation in southern Finland. The species-area refinement resulted in a network of significantly larger sites with minor trade-offs with representation (numbers of populations). Giving endangered species higher weights ensured that the trade-off occurred mostly between site size and representation of low-priority species. We recommend using a species-area refinement for practical, maximum-coverage conservation planning.  相似文献   
488.
Abstract:  Not all species are likely to be equally affected by habitat fragmentation; thus, we evaluated the effects of size of forest remnants on trophically linked communities of plants, leaf-mining insects, and their parasitoids. We explored the possibility of differential vulnerability to habitat area reduction in relation to species-specific and food-web traits by comparing species–area regression slopes. Moreover, we searched for a synergistic effect of these traits and of trophic level . We collected mined leaves and recorded plant, leaf miner, and parasitoid species interactions in five 100-m2 transects in 19 Chaco Serrano woodland remnants in central Argentina. Species were classified into extreme categories according to body size, natural abundance, trophic breadth, and trophic level . Species–area slopes differed between groups with extreme values of natural abundance or trophic specialization. Nevertheless, synergistic effects of life-history and food-web traits were only found for trophic level and trophic breadth: area-related species loss was highest for specialist parasitoids. It has been suggested that species position within interaction webs could determine their vulnerability to extinction. Our results provide evidence that food-web parameters, such as trophic level and trophic breadth, affect species sensitivity to habitat fragmentation .  相似文献   
489.
490.
赵劲松 《环境化学》2013,(7):1188-1193
利用贝叶斯统计方法构建了基于区间活性数据的取代苯胺和苯酚类化合物对大型溞(Daphniamagna)24 h急性毒性的定量结构-活性关系模型,并与基于平均数和中位数的点估计活性数据的定量结构-活性关系模型进行了比较.结果表明,前者可以充分利用化合物的活性数据信息,模型具有更好的拟合效果与预测能力以及较宽的应用范围.基于区间活性数据的定量结构-活性关系模型可为生态风险评价等提供更加可靠的预测数据.  相似文献   
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