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As a contribution to the long-term emergence studies carried out as part of the “Breitenbach ecosystem project”, this paper presents the results obtained on emergence patterns and population dynamics of blackflies from 1984 to 1988. The Breitenbach is a small first order stream near Schlitz/Hesse, running into the Fulda river. Adult blackflies were caught in 4 greenhouse emergence traps, each spanning the whole width of the stream for a length of 6 m. A manual and then a partly automated method for collecting trapped insects was applied for three years and one year, respectively. Sixteen blackfly-species of different origin were found in the traps: a) autochthonous species: Prosimulium tomosvaryi, Simulium vernum s.l., S. cryophilum s.l., S. ornatum s.l. (common); S. costatum, S. trifasciatum, S. monticola, S. argyreatum (rare); b) species of doubtful origin: S. lundstromi, S. angustitarse, S. angustipes, S. aureum (very rare); c) allochthonous species: S. lineatum, S. equinum, S. erythrocephalum, S. noelleri. It was shown that the last 4 species had not emerged from the Breitenbach but had flown into the traps as adults. In addition, females of autochthonous species with blood or with mature eggs were trapped, which were also considered to have flown in. Besides revealing a limitation of the trap construction, they supported the detailed interpretation of some intricated patterns of appearance. Variations in emergence patterns and specimen numbers between years and traps were pronounced, but only in a few cases could they be attributed to changes in abiotic factors such as water temperature or discharge. P. tomosvaryi had the most simple and regular life cycle, with one well synchronised emergence peak annually from April to May (or even to June). No gradient of specimen numbers along the stream was evident. The two closely related species S. vernum and S. cryophilum had quite similar emergence patterns: There were two broad peaks per year, extending mainly from March to June and from July to October or November. In some cases the number and separation of consecutive generations was not clear. The abundance of both species clearly decreased downstream, more so for S. cryophilum than for S. vernum. In a trap closest to a tributary spring, S. cryophilum was the dominant species during three of the four years examined. The adults of S. ornatum displayed an intricate pattern of appearance, with very low specimen numbers in spring and medium to very high numbers in July/August and September/October. S. ornatum is the only blackfly species that inhabits both the Breitenbach and the adjacent section of the Fulda river. It was shown that females emerging from the Fulda river regularly invade the Breitenbach valley in greatly varying numbers and oviposit there. This leads to overlapping larval cohorts with corresponding emergence peaks. Although S. ornatum was the most abundant species in one year in the lower traps (60 to 80% of all individuals), it remains uncertain whether it is a long-term, permanent member of the autochthonous blackfly fauna of the Breitenbach. Estimates of total numbers of flown-in adults, actual emergence, dry weight biomass, the ecological separation of the species and their life cycle strategies are discussed. 相似文献
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基于2010年第六次全国人口普查微观数据和夜间灯光数据等,运用多层级logistic回归模型估计中国城镇化水平和速度与老年人自评健康的关联,分析城镇化健康效应在不同老年人群体间的差异,并运用倾向得分匹配方法,控制“自选择”机制对分析结果的干扰。结果表明：1）中国县区城镇化水平和速度与老年人自评健康呈显著正相关关系,居住于城镇化水平中等和城镇化速度较快县区的老年人更可能自评为健康;2）城镇化水平和速度与老年人自评健康的关系在不同受教育程度和户口状态的老年人群体间存在显著差异,城镇化水平和速度对受教育程度较低、持有本地户口老年人健康水平的提升效益更大;3）控制了老年人居住“自选择”的干扰后,县区城镇化水平和速度与老年人自评健康的正向关联依然稳健,表明“自选择偏误”对中国县区城镇化水平和速度与老年人自评健康的关系没有显著的影响。 相似文献
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Although China was one of the countries with the fastest-growing aging population in the world, limited scholarly attention has been paid to migration among older adults in China. The full picture of their migration in the entire country over time remains unknown. This study examines the spatial patterns of older interprovincial migration flows and their drivers in China over the period 1995 to 2015, using four waves of census data and intercensal population sample survey data. Results from eigenvector spatial filtering negative binomial regressions indicate that older adults tend to migrate away from low cost-of-living rural areas to high cost-of-living urban and rural areas, moving away from areas with extreme temperature differences. The location of their grandchildren is among the most important attractions. Our findings suggest that family-oriented migration is more common than amenity-led migration among retired Chinese older adults, and the cost-of-living is an indicator of economic opportunities for adult children and the quality of senior care services. 相似文献
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A model describing macroalgal early life stages and adult dynamics was used to quantify the effects of non-adult forms on the productivity of adult macroalgae in a eutrophic estuary. Predictions indicate that during years with mild winters and low rainfall, spring blooms will occur at the expense of the growth and reproduction of overwintering adults and without the contribution of the spore bank. In these circumstances, there is a positive correlation between the intensity of the blooms and the biomass of overwintering adults until a maximum threshold value. On the contrary, in years with high rainfall and low or inexistent biomass of overwintering adults, the onset of adult’s growth depends on the biomass of viable dormant spores, the growing season occurs later and adult productivity is very limited. Long-term predictions for climate change scenarios suggest that, in general, global warming will have adverse affects on Ulva intestinalis productivity, with the adults being more affected than the early life stages. 相似文献
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Evelyn Blumenberg Anne Brown Kelcie Ralph Brian D. Taylor Carole Turley Voulgaris 《Urban geography》2013,34(9):1375-1397
ABSTRACTSome have heralded a resurgence of urban living in the U.S., particularly among young adults. Are Americans abandoning suburbs in favor of more urban lifestyles? What is the scope and scale of this urban resurgence? We develop a typology of neighborhoods to analyze the residential location of young and older U.S. adults from 2000 to 2011–15. Census and national travel survey data reveal that suburban population growth continues to outpace that in urban neighborhoods. Although young adults are more likely than older adults to live in urban neighborhoods, recent urban population growth is neither associated with suburban decline, nor being led by young adults. Significant recent population growth in the newest, suburban neighborhoods suggests that greenfield development remains the primary means to increase American housing supply. Shifting metropolitan growth from the suburban fringe would likely require expanding housing supply in urban neighborhoods, and bringing urban amenities to established inner-ring suburbs. 相似文献
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Junfeng Zhang 《Cretaceous Research》1999,20(6):813
Undoubted fossil nymphs of the family Aeschnidiidae within the Aeschnidioidea of the Anisoptera, Odonata are identified and described and their phylogenetic relationship and bioecological characteristics are deduced. The nymphs discovered previously in China, Mongolia and Russia and considered to be aeschnidiids are, in fact, unrelated to this group. All nine Chinese species in six genera can be merged into one alone, Aeschnidium heishankowense. It is the first animal from the ‘Jehol biota’ of East Asia to be linked with the species known from the Lower Tithonian of Germany. The geological age of the oldest strata bearing the fossil nymphs is debatable; it could be latest Jurassic rather than Early Cretaceous. 相似文献
8.
在有关养老的老年学和地理学研究中,“就地养老”是一个广泛使用的概念,并一直被认为是解决老龄人口养老需求的有效政策手段。迄今为止,关于就地养老的研究主要关注了很多能够让老年人健康就地(或在家)养老的物质方面的因素,比如住房条件或家庭照护。有些老年学研究者们认识到,就地养老受到居住环境中实体环境和社会、情感因素的共同影响。但我们认为,在养老体验研究中,要更加深入地审视“人”和“地方”之间的复杂关系。特别是,我们主张就地养老成功的因素是地方具有维持良好关系的潜力。提到“地方(place)”一词的时候,人们过分局限于关注老年人身体上接近的地理空间,或是具有实体边界的地方,例如房子或社区。而我们通过回顾现有文献发现,对许多选择就地养老的人来说,更具有意义的是随着时间的推移,他们在不同空间尺度上所建立起来的多元的、网络化的社会和非社会关系。基于这个新的视角,可以更好地理解老年人与地方的多层次的联系,以及从不同尺度和不同类型的人与地方的关系来考察就地养老的意义。 相似文献
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基于广州13个社区问卷调查数据,运用多元线性回归模型探讨老年人“旁路”就医距离特征及其影响因素,结果发现：1）广州老年人小病及慢性病旁路就医距离以1 km为“就地—旁路”临界点,以5 km为“近旁路—远旁路”临界点,形成核心—边缘旁路就医圈层;2）男性老年人比女性老年人旁路就医距离更远;3）居住社区类型是影响旁路就医距离的关键因素,医疗级配不均对旁路就医距离远近影响较大,也是城乡社区老年人旁路就医距离差异化的重要原因;4）对社区越满意的老年人更倾向选择社区内就地就医。倾向特征、使能资源和医疗需求共同影响老年人旁路就医行为的距离远近,进而影响老年人健康公平结果。 相似文献
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Older people are typically characterized as recipients of care who make ever increasing demands on overstretched and underfunded social care services. This article is about older people as givers of care to nonhousehold members. It draws on an in-depth study of volunteering in an English community beset by concentrated poverty and worklessness. Older adults, especially women, make up a significant component of those who give time through volunteering for organizations that provide social welfare services for people in need in that community. Although older adults had diverse ways of thinking about volunteering, they often undertook the effort as an expression of care and support to others. 相似文献