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721.
To investigate vertical changes of bacterial communities from living plants to the associated sediments and bacterial biogeochemical roles in peatland ecosystem,samples of different part of individual Sphagnum palustre and the different layers of the underlying sediments were collected from Dajiuhu Peatland in central China.All samples were subject to 16S rRNA gene clone libraries and quantitative PCR analysis.Even though bacteria vary in abundance at the same order of magnitude in all samples,they show great profile difference in composition from the top part of S.palustre to the low layer of the sediments.Cyanobacteria and alpha-Proteobacteria dominate at the top part whereas Acidobacteria at the middle part of S.palustre.Alpha-Proteobacteria and Acidobacteria are the dominant phyla at the bottom part of S.palustre and in the surface peat sediment.In contrast,bacterial communities in the subsurface sediments are dominated by Acidobacteria.These profile distributions of different bacterial communities are closely related to their ecological functions in the peatland ecosystem.Specifically,most Cyanobacteria were observed at the top green part of S.palustre,a horizon where the active photosynthesis of the moss occurs,which infers their endosymbiosis.In contrast,Acidobacteria,dominant in the subsurface sediments,are able to decompose the specific compounds on the cell wall of Sphagnum moss and thus might play an important role in the formation of the peatland,including the acidic condition.Methane oxidizing process might have been underestimated in Sphagnum peatland due to the identification of Methylocystaceae in all parts of the moss investigated here.The vertical difference in bacterial composition and bacterial ecological functions presented here sheds light on the understanding of biogeochemical processes,in particular the CH4 flux,in peat ecosystems. 相似文献
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中国农村空心化问题研究的进展与展望 总被引:58,自引:6,他引:52
改革开放以来,中国快速城镇化和人口非农化,在促进农民就业和增收的同时,加快了农村空心化发展,致使空心村问题日趋严峻。本文通过梳理国内农村空心化的研究进展,简要分析了相关研究的主要特点与不足,探讨了今后针对农村空心化与空心村问题的创新研究领域和方向。在国家坚守18亿亩耕地红线、推进社会主义新农村建设和促进城乡统筹发展的时代背景下,系统分析空心化村庄用地结构与潜力、类型及演进规律,深入研究农村空心化情景模拟与调控、空心村整治规划示范与配套政策,以及空心化村庄整治与管理决策支持系统等,既是推进乡村地域系统的理论创新和深化实证研究的需要,也是面向国家战略需求提供科技决策服务的需要。 相似文献
726.
旅游地社区参与度熵权层次分析评价模型与应用 总被引:4,自引:1,他引:3
建立旅游地社区参与度熵权层次分析评价模型,以周庄、同里、西递、宏村为研究对象,对我国传统村镇旅游地社区参与度进行定量评价。研究表明:(1)旅游规划与决策参与度是影响传统村镇旅游地社区总体参与度的关键性因素;(2)西递处于社区高度参与状态,周庄、同里、宏村处于社区中度参与状态,四个旅游地社区参与度由大到小的顺序为:西递>周庄>同里>宏村;(3)我国传统村镇旅游地居民参与旅游规划与决策的程度偏低,成为影响社区参与度总体得分和社区参与层次的主要原因;(4)导致社区参与度差异的主要因素为传统村镇旅游地在景区经营管理模式、旅游地社会经济发展阶段、社区旅游制度和政策、社区形态与旅游资源属性上存在差异。 相似文献
727.
Kathleen C. Parker 《The Professional geographer》1987,39(1):47-58
Discriminant analysis is used to identify relationships between vegetation structure and nesting behavior in 78 breeding bird communities in North America. Results indicated that bird communities associated with structurally similar vegetation exhibited similar arrays of nesting habits despite their geographical separation. Tree-cavity, intermediate-cup, and high-cup nesters dominated forests and woodlands; ground-cup and ground-scrape nesters dominated grasslands; and low-cup nesters dominated desert, scrub, and some woodland sites. These functional relationships are distinct from previously reported continental scale relationships between avian feeding habits and gross vegetation structure. Links between nesting behavior and vegetation structure provide us, as geographers, with a means for placing birds into a physical landscape perspective. 相似文献
728.
《The Professional geographer》1985,37(3):357-389
Book Reviewed in this article: Redundant Spaces in Cities and Regions? Studies in Industrial Decline and Social Change . J. Anderson, S. Duncan and R. Hudson. eds. The Social Consequences and Challenges of New Agricultural Technologies . Gigi M. Berardi and Charles C. Geisler, eds. Determinants of Fertility in Developing Countries, Vol. I, Supply and Demand for Children . Rodolfo A. Bultao and Ronald D. Lee, eds. Computer Mapping: Progress in the‘80s . James R. Carter. Washington: Colonial Africa . A. J. Christopher. Geography of the Soviet Union . J. P. Cole. Chicago Mapmakers, Essays on the Rise of the City's Map Trade . Michael P. Conzen, ed. Changes in the Land: Indians, Colonists and the Ecology of New England . William Cronon. Mizner's Florida: American Resort Architecture . Donald W. Curl. Geographical Studies on the Soviet Union: Essays in Honor of Chauncy D. Harris . George Demko and Roland J. Fuchs, eds. Fluvial Hydrology . S. Lawrence Dingman. Pueblo Indian Water Rights: Struggle For a Precious Resource . Charles T. DuMars, Marilyn O'Leary and Albert E. Utton. Women in the Cities of Asia: Migration and Urban Adaptation . James T. Fawcett, Siew-Ean Khoo, and Peter C. Smith, eds. America's National Parks and Their Keepers . Ronald A. Foresta. Neighborhood Revitalization and the Postindustrial City . Dennis E. Gale. China in Canada: A Dialogue on Resources and Development . R. Louis Gentilcore, ed. China: The 80s Era . Norton Ginsburg and Bernard A. Lalor, eds. Boulder, CO: Global Resources: Challenges of Interdependence . Martin I. Glassner, ed. River Networks . Texas: A Geography . Terry G. Jordan with John L. Bean, Jr. and William M. Holmes. The American Frontier: An Archaeological Study of Settlement Pattern and Process . Kenneth E. Lewis. Water Resources, Geography and Law . Olen Paul Matthews. A Field Guide to American Houses . Virginia and Lee McAlester. Population: Patterns, Dynamics, and Prospects . James L. Newman and Gordon E. Matzke. Wood, Brick, and Stone, The North American Settlement Landscape, Vol. 1: Houses . Allen G. Noble. Historical Analysis in Geography . William Norton. The Displaced Worker and Community Response: Case Study of Portsmouth, Scioto County, Ohio . H. Milton Patton and Janet W. Patton. Disaster Management: Warning Response and Community Relocation . Ronald W. Perry and Alvin H. Muskatel. The Anthropology of Space: Explorations into the Natural Philosophy and Semantics of the Navajo . Rik Pinxten, Ingrid van Dooren, and Frank Harvey. What STYLE Is It? A Guide To American Architecture . John C. Poppeliers, S. Allen Chambers, Jr., and Nancy B. Schwartz. Appalachia: A Regional Geography—Land, People and Development . Karl Raitz and Richard Ulack. An Introduction to Urban Geography . John R. Short. Ford, A Village in the West Highlands of Scotland: A Case Study of Repopulation and Social Change in a Small Community . John B. Stephenson. Income and Jobs: USA Diagnosing the Reality . George Sternlieb and James W. Hughes. Weather and Climate of the Antarctic . W. Schwerdtfeger. History and Ecology: Studies of the Grassland, James C. Malin . Robert P. Swierenga, ed. Optimal Control of Spatial Systems . K. C. Tan and R. J. Bennett. Social Science and Revolutions . Stan Taylor. The Global Textile Industry . Brian Toyne, Jeffrey S. Arpan, David A. Ricks, Terence A. Shimp and Andy Barnett. Integrated Water Development: Water Use and Conservation Practice in Western Colorado . James L. Wescoat, Jr. Proceedings of the First International Symposium on Maps and Graphics for the Visually Handicapped . Joseph W. Wiedel, ed. 相似文献
729.
The housing loss assessment of rural villages caused by earthquake disaster in Yunnan Province 总被引:1,自引:0,他引:1
Introduction In accordance with the systematical theory of natural disaster, the intensity of disaster-causing factor and the frangibility of the disaster-bearing body decide the disaster degree (SHI, 1991, 2002). The building facilities is the uppermost disaster-bearing body in the earthquake disaster system, as the population and fortune in the city are concentrated, the density of the housings is large, the antiseismic and disaster reduction of the city have always been an important aspect… 相似文献
730.
Sarah Blandy 《GeoJournal》2006,66(1-2):15-26
It is important to analyse the growth of gated communities and the drivers for their supply and demand, within the context
specific to each country’s history. This article uses findings from recent studies of gated communities in England, together
with historical material, to explore their typology. It considers the changing social, economic and political conditions which
may lead to the emergence of defended collective housing, together with the history of property relations and the concept
of public/private land within the English context. 相似文献