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1.
以贵州花江峡谷花椒(Zanthoxylum bungeamun)林为研究对象,采用16S rRNA高通量测序技术,分析种植5、10、20、30 a花椒根际土壤细菌群落结构和多样性特征,探讨不同种植年限花椒土壤理化因子对根际细菌群落分布的影响,为喀斯特石漠化地区花椒农业可持续发展提供有效的理论依据。结果表明,随着花椒种植年限的增加,土壤含水率、pH和有效磷逐渐升高,有机质、铵态氮和硝态氮含量先降低后升高(P<0.05)。根际土壤细菌Shannon、Simpson指数总体呈现上升趋势,OTUs、Chao1指数在10a较低。PCo A分析显示,不同种植年限花椒根际细菌群落组成差异显著,并且随着年限的增加,群落结构趋于相似;差异指示种分析表明,5—30a差异指示种分别为Firmicutes(厚壁菌门)、Cyanobacteria(蓝藻菌门)、Planctomycetes(浮霉菌门)、Entotheonellaeota(肠杆菌门)。RDA分析表明,有机质和含水率与细菌群落分布显著相关(P<0.05)。系统发育多样性分析表明,丰富类群多样性与环境因子存在较多的正相关,稀有类群比丰富类群有更强的发育信号。Bug Base预测分析发现:随着年限增加根际土壤好氧细菌增加,厌氧细菌下降,5、10 a氧化胁迫耐受菌低于20、30 a,致病菌在5、10 a高于20、30 a。综上,种植年限影响了花椒根际土壤细菌群落多样性,不同年限根际土壤肥力不同使得土壤细菌选择性生长,随着一定时间发育花椒抗病能力提高。  相似文献   
2.
长江经济带研究文献分析   总被引:2,自引:0,他引:2  
长江经济带是我国国土空间开发最重要的东西轴线,近年来推动长江经济带发展逐步上升为新一轮的国家战略。而自长江经济带初步构想于20世纪80年代提出以来,我国学者对长江经济带进行了诸多方面的研究。通过相关研究的文献分析,了解分析文献来源规律,梳理总结文献研究内容,有利于相关学术研究的推进。在查阅了大量相关文献的基础上,首先对文献来源进行分析,接着对长江经济带的概念与范围进行了辨析,再从发展战略、产业发展、交通建设、区域经济差异、区域空间结构、区域协调与合作、地区与长江经济带关系与生态环境等8个方面的对文献内容进行归纳总结与探讨,最后从加强交流合作、宏观微观结合、经典理论应用、关注交通研究、流域联动机制及视野动态开阔等方面对新时期长江经济带研究进行展望。  相似文献   
3.
Species, habitats, and ecosystems are increasingly exposed to multiple anthropogenic stressors, fueling a rapidly expanding research program to understand the cumulative impacts of these environmental modifications. Since the 1970s, a growing set of methods has been developed through two parallel, sometimes connected, streams of research within the applied and academic realms to assess cumulative effects. Past reviews of cumulative effects assessment (CEA) methods focused on approaches used by practitioners. Academic research has developed several distinct and novel approaches to conducting CEA. Understanding the suite of methods that exist will help practitioners and academics better address various ecological foci (physiological responses, population impacts, ecosystem impacts) and ecological complexities (synergistic effects, impacts across space and time). We reviewed 6 categories of methods (experimental, meta-analysis, single-species modeling, mapping, qualitative modeling, and multispecies modeling) and examined the ability of those methods to address different levels of complexity. We focused on research gaps and emerging priorities. We found that no single method assessed impacts across the 4 ecological foci and 6 ecological complexities considered. We propose that methods can be used in combination to improve understanding such that multimodel inference can provide a suite of comparable outputs, mapping methods can help prioritize localized models or experimental gaps, and future experiments can be paired from the outset with models they will inform.  相似文献   
4.
We discuss how confirmatory factor analysis results should be used to examine potential higher‐order constructs and advocate that researchers present five types of evidence, which are as follows: (1) the ability of the higher‐order model to reproduce the observed covariation among manifest variables; (2) the ability of the higher‐order model to reproduce the observed covariation among manifest variables better than more parsimonious alternative models—and no less well than less parsimonious alternative models; (3) the ability of the higher‐order model to reproduce the observed covariation among lower‐order factors; (4) the ability of the higher‐order factor to explain variation in lower‐order factors; and (5) the ability of the higher‐order factor to explain variation in manifest variables. We illustrate how this type of evidence could be presented with a worked example and contrast our recommendations with the manner in which higher‐order confirmatory factor analysis has been used in the organizational sciences over the past 25 years to support claims regarding higher‐order constructs such as core self‐evaluations and transformational leadership. Our review shows that a substantial proportion of the 44 examined articles failed to present enough evidence to allow readers to understand the size and importance of higher‐order factors. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
5.
针对大型商用飞机对核电厂反应堆安全壳恶意撞击的安全评估需求,综述了国外确定飞机撞击安全壳载荷曲线的基础理论、试验测试技术和数值模拟方法.首先,从理论上对飞机撞击安全壳的载荷特性和Riera撞击模型进行分析,给出了Riera模型的基本假设、模型各项物理意义及模型的求解方法,明确了靶体碰撞表面的冲击载荷(力)由静载项和动载项组成;其次,分析总结了确定Riera模型中压损载荷参数的试验方法和真实飞机撞击载荷测量的试验技术和实施方法,指出大型商用飞机对核电厂反应堆安全壳恶意撞击属"软冲击"范畴,撞击载荷可用Riera模型计算得到;再者,在数值模拟方面,总结了采用有限元技术进行飞机撞击载荷计算和安全评估的数值模拟方法及其发展趋势;最后,在分析国内开展飞机撞击载荷研究面临问题的基础上,指出从理论上建立飞机撞击载荷-时间曲线计算模型及方法,并通过试验和数值模拟验证是国内确定大型商用飞机撞击安全壳结构载荷曲线比较可行的技术路线.  相似文献   
6.
While the public can play a vital role in saving lives during emergencies, intervention is only effective if people have the skills, confidence, and willingness to help. This review employs a five-stage framework to systematically analyse first aid and emergency helping literature from 22 countries (predominately in Asia, Australia, Europe, and the United States). The review covers 54 articles that investigate public first-aid knowledge and uptake of first-aid training (40); public confidence in first-aid skills and willingness to help during an emergency (21); and barriers to or enablers of learning first aid and delivering first aid in an emergency (25). The findings identify high levels of perceived knowledge, confidence, and willingness to help, supporting the contention that the public can play a vital role during an emergency. However, the findings also point to low uptake levels, low tested skill-specific knowledge, and barriers to learning first aid and helping, indicating that the first-aid training landscape is in need of improvement.  相似文献   
7.
8.
To reduce future loss of biodiversity and to allocate conservation funds effectively, the major drivers behind large‐scale extinction processes must be identified. A promising approach is to link the red‐list status of species and specific traits that connect species of functionally important taxa or guilds to resources they rely on. Such traits can be used to detect the influence of anthropogenic ecosystem changes and conservation efforts on species, which allows for practical recommendations for conservation. We modeled the German Red List categories as an ordinal index of extinction risk of 1025 saproxylic beetles with a proportional‐odds linear mixed‐effects model for ordered categorical responses. In this model, we estimated fixed effects for intrinsic traits characterizing species biology, required resources, and distribution with phylogenetically correlated random intercepts. The model also allowed predictions of extinction risk for species with no red‐list category. Our model revealed a higher extinction risk for lowland and large species as well as for species that rely on wood of large diameter, broad‐leaved trees, or open canopy. These results mirror well the ecological degradation of European forests over the last centuries caused by modern forestry, that is the conversion of natural broad‐leaved forests to dense conifer‐dominated forests and the loss of old growth and dead wood. Therefore, conservation activities aimed at saproxylic beetles in all types of forests in Central and Western Europe should focus on lowlands, and habitat management of forest stands should aim at increasing the amount of dead wood of large diameter, dead wood of broad‐leaved trees, and dead wood in sunny areas.  相似文献   
9.
Most of China's 24–28 primate species are threatened with extinction. Habitat reduction and fragmentation are perhaps the greatest threats. We used published data from a conservation genetics study of 5 endangered primates in China (Rhinopithecus roxellana, R. bieti, R. brelichi, Trachypithecus francoisi, and T. leucocephalus); distribution data on these species; and the distribution, area, and location of protected areas to inform conservation strategies for these primates. All 5 species were separated into subpopulations with unique genetic components. Gene flow appeared to be strongly impeded by agricultural land, meadows used for grazing, highways, and humans dwellings. Most species declined severely or diverged concurrently as human population and crop land cover increased. Nature reserves were not evenly distributed across subpopulations with unique genetic backgrounds. Certain small subpopulations were severely fragmented and had higher extinction risk than others. Primate mobility is limited and their genetic structure is strong and susceptible to substantial loss of diversity due to local extinction. Thus, to maximize preservation of genetic diversity in all these primate species, our results suggest protection is required for all sub‐populations. Key priorities for their conservation include maintaining R. roxellana in Shennongjia national reserve, subpopulations S4 and S5 of R. bieti and of R. brelichi in Fanjingshan national reserve, subpopulation CGX of T. francoisi in central Guangxi Province, and all 3 T. leucocephalus sub‐populations in central Guangxi Province.  相似文献   
10.
One of the main goals of conservation biology is to understand the factors shaping variation in biodiversity across the planet. This understanding is critical for conservation planners to be able to develop effective conservation strategies. Although many studies have focused on species richness and the protection of rare and endemic species, less attention has been paid to the protection of the phylogenetic dimension of biodiversity. We explored how phylogenetic diversity, species richness, and phylogenetic community structure vary in seed plant communities along an elevational gradient in a relatively understudied high mountain region, the Dulong Valley, in southeastern Tibet, China. As expected, phylogenetic diversity was well correlated with species richness among the elevational bands and among communities. At the community level, evergreen broad‐leaved forests had the highest levels of species richness and phylogenetic diversity. Using null model analyses, we found evidence of nonrandom phylogenetic structure across the region. Evergreen broad‐leaved forests were phylogenetically overdispersed, whereas other vegetation types tended to be phylogenetically clustered. We suggest that communities with high species richness or overdispersed phylogenetic structure should be a focus for biodiversity conservation within the Dulong Valley because these areas may help maximize the potential of this flora to respond to future global change. In biodiversity hotspots worldwide, we suggest that the phylogenetic structure of a community may serve as a useful measure of phylogenetic diversity in the context of conservation planning.  相似文献   
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