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991.
After losing much of their demographic vitality under communism, rural areas of Eastern Europe are now handicapped by greatly
reduced commuting opportunities and by a lack of foreign investment in the countryside. Although restitution and privatisation
has placed much of the land under the control of private farmers, there is a need to modernise agriculture and rural infrastructure
generally and also to increase the scope for pluriactivity. At the same time, functional links with the towns must be restored
through a growth of employment linked with the central place system. Despite the importance of private enterprise under the
conditions of a market economy, the government must take a lead and this paper deals with initiatives taken in rural Slovakia
to mobilise the human resources of the countryside. The paper is heavily oriented towards research by the geographers at Nitra
who have been much involved with the transformation of their local area. It is evident that while there has been no shortage
of ideas, progress has been limited on account of low investment and the tensions associated with a series of three Meciar
governments which have dominated Slovak politics through the 1990s.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
992.
993.
湿地可持续经营认证可以提高湿地的经营水平,实现湿地资源保护与利用的有机统一。采用SWOT方法对中国开展湿地可持续经营认证的优势(S)、劣势(W)、机遇(O)和挑战(T)进行分析,为制定和实施湿地可持续经营认证提出相应的方法与途径。SWOT分析结果表明:目前在中国存在湿地资源丰富、各级政府高度重视湿地保护等优势,但我国在湿地可持续经营认证方面存在市场需求有限、管理水平低等劣势。这些优势和劣势给湿地可持续经营认证的推进带来了巨大的挑战与机遇。开展湿地可持续经营认证,需要充分评估湿地环境的基本状况、自我修复与维持能力以及人为生产经营管理过程的有效性和合理性,同时对湿地产品的品质与安全性进行检验认证,建议尽快启动湿地可持续经营认证工作。 相似文献
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996.
This paper addresses the issue of the non conservation of tracer that occurs when a leapfrog time stepping scheme is used in association with a Robert-Asselin time filter within the framework of a time varying vertical coordinate system. A re-formulation of both the forcing and filtering terms that provides a globally conservative scheme is presented. Local conservation is then achieved when the model levels and subsequently the sea surface height satisfy a local compatibility condition. The properties of the resulting scheme are illustrated by a global coupled ocean–sea ice model based on the Nucleus for European Modelling of the Ocean (NEMO). 相似文献
997.
Enric Ballesteros Joaquim Garrabou Bernat Hereu Mikel Zabala Emma Cebrian Enric Sala 《Estuarine, Coastal and Shelf Science》2009
Populations dominated by Cystoseira zosteroides, an endemic and threatened Mediterranean seaweed, colonize deep-water rocky habitats down to more than 50 m depth. Assemblages dominated by this species display high algal and invertebrate species richness. Algal biomass averages 1134 g dw m−2. Erect and turf algae account for only 25% of total algal dry weight, while encrusting corallines are responsible for the remaining 75%. Sponges, bryozoans and ascidians constitute the dominant sessile macrofauna. Cystoseira zosteroides is the dominant erect algae, with a mean biomass of 60.6 g dw m−2, and densities ranging from 4 to 7 plants m−2. The alien turf alga Womersleyella setacea has a biomass of 104.2 g dw m−2 and covers most of the understory substrate. The size-frequency distribution of C. zosteroides populations shows differences over time. Mean annual growth of the main axis is around 0.5 cm and mean annual mortality rate is lower than 2%. Recruitment was almost nil during the studied period of time (10 years). Processes structuring these deep-water Cystoseira stands must be driven by episodic disturbances, after-disturbance recruitment pulses, and long periods of steady growth that last at least 10 years. However, it is also possible that recruitment is irreversibly inhibited by the alien alga W. setacea in which case these old-growth stands are faced with extinction. The highly diversified assemblages and the low growth and low mortality rates of C. zosteroides indicate high vulnerability to natural and anthropogenic disturbances, and call for effective measures to ensure their conservation. 相似文献
998.
Sandy beach ecosystems: key features, sampling issues, management challenges and climate change impacts 总被引:4,自引:0,他引:4
Thomas A. Schlacher Dave S. Schoeman Jenifer Dugan Mariano Lastra Alan Jones Felicita Scapini & Anton McLachlan 《Marine Ecology》2008,29(S1):70-90
Escalating pressures caused by the combined effects of population growth, demographic shifts, economic development and global climate change pose unprecedented threats to sandy beach ecosystems worldwide. Conservation of beaches as functional ecosystems and protection of their unique biodiversity requires management interventions that not only mitigate threats to physical properties of sandy shores, but also include ecological dimensions. Yet, beach management remains overwhelmingly focused on engineering interventions. Here we summarise the key outcomes of several workshops, held during the 2006 Sandy Beach Ecology Symposium in Vigo, Spain, that addressed issues of climate change, beach management and sampling methodology. Because efficient communication between managers and ecologists is critical, we summarise the salient features of sandy beaches as functional ecosystems in 50 'key statements'; these provide a succinct synopsis of the main structural and functional characteristics of these highly dynamic systems. Key outcomes of the workshops include a set of recommendations on designs and methods for sampling the benthic infaunal communities of beaches, the identification of the main ecological effects caused by direct and indirect human interventions, the predicted consequence of climate change for beach ecosystems, and priority areas for future research. 相似文献
999.
A Corrected Incompressible SPH (CISPH) method is proposed for accurate tracking of water surface in breaking waves. Corrective terms are derived based on a variational approach to ensure the angular momentum preservation of Incompressible SPH (ISPH) formulations. The proposed CISPH method is applied to solve the Navier–Stokes equation for simulating the breaking and post-breaking of solitary waves on a plane slope. The enhanced precision (compared to the ISPH method) of the CISPH method is confirmed through both qualitative and quantitative comparisons with experimental data. The introduction of corrective terms significantly improves the capability and the accuracy of the ISPH method in the simulation of wave breaking and post-breaking. 相似文献
1000.
Chanda L. Meek Amy Lauren Lovecraft Martin D. Robards Gary P. Kofinas 《Marine Policy》2008,32(6):1080-1089
Arctic coastal communities in the Bering Strait region of Alaska (USA) and Chukotka (Russia) share a close relationship with their natural environments that can be characterized as a social–ecological system. This system is complex, featuring changing ecosystem conditions, multiple jurisdictions, migratory animal populations, and several cultures. We argue that linkages between communities in both countries enhance the effectiveness of transborder polar bear and walrus conservation. We find that locally embedded bilateral institutions can provide effective management venues that persist despite slow or lacking processes of international law because they provide a better fit between rules for managing and the true system state. 相似文献