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281.
A stage structured population (SSP) model based on Fennel's [Fennel, W., 2001. Modelling copepods with links to circulation models. Journal of Plankton Research, 23, 1217–1232] equations is applied to Centropages typicus (Kröyer), a dominant copepod species of the North Western Mediterranean Sea (NWMS) and a prey of small pelagic fish. The model considers five groups of stages and development rates are represented by a mechanistic formulation depending on individual specific growth in each stage. Individual growth is calculated from the individual energy budget depending on food availability and temperature.  相似文献   
282.
1Catastrophology is an extremely importantnatural- social science.Health and longevity are the common wishes of humanity,and peace and progress are thecommon goals of society.Calamities,either natural or human,are harmful to the health andlongevity of human beings,bring about economic damages and impede the prosperity andprogress of human society. The phylogeny of human society is indeed a chronicle of struggleswith various disasters.To date,the study of disasters and hazards has developed int…  相似文献   
283.
江汉平原建设用地扩张的时空特征与驱动力分析   总被引:2,自引:0,他引:2  
建设用地的迅速扩张已经成为当前中国土地利用变化的主要特征。以中国科学院土地利用数据库(基于1995、2000和2005TM影像)为基础,利用GIS空间叠加分析和缓冲区分析技术,提取建设用地变化及其空间分布信息,运用建设用地扩张速度和强度指数对江汉平原1995~2005年10 a来建设用地扩张的时空特征进行了研究。在此基础上,结合各县市的社会经济等信息,运用灰色关联分析,对建设用地扩张的驱动力进行探讨。结果显示:总体上江汉平原建设用地扩张速度呈现增大趋势,但各县市之间扩张差异显著;各县市建设用地扩张分布上呈现组团状特点;沿交通线扩张的特征较为突出,尤其是后一阶段增幅高于前一阶段,沿江扩张增幅明显;总人口的增长是江汉平原建设用地扩张最主要的驱动力;交通条件改善、经济发展与区域建设用地扩张也有明显的相关关系  相似文献   
284.
Time series of abundance estimates are commonly used for analyses of population trends and possible shifts in growth rate. We investigate if trends in age composition can be used as an alternative to abundance estimates for detection of decelerated population growth. Both methods were tested under two forms of density dependence and different levels of environmental variation in simulated time series of growth in Baltic gray seals. Under logistic growth, decelerating growth could be statistically confirmed after 16 years based on population counts and 14 years based on age composition. When density dependence sets in first at larger population sizes, the age composition method performed dramatically better than population counts, and a decline could be detected after 4 years (versus 10 years). Consequently, age composition analysis provides a complementary method to detect density dependence, particularly in populations where density dependence sets in late.  相似文献   
285.
We studied the changes in wetland habitats and waterbird communities between the 1980s and the 2000s at Chongming Dongtan, a Ramsar site in the Yangtze River estuary, an ecologically important region. This region is an important stopover site for shorebirds along the East Asian–Australasian flyway and is extensively used by waterfowl. A net loss of 11% of the wetland area was estimated during study periods at Chongming Dongtan. The change was dependent on wetland types: while the area of artificial habitats such as paddy fields and aquacultural ponds more than doubled, more than 65% of natural habitats including sea bulrush (Scirpus mariqueter) and common reed (Phragmites australis) marshes were lost over the two decades. An exotic plant species introduced from North America, smooth cordgrass (Spartina alterniflora), occupied 30% of the vegetated intertidal zone by the 2000s. Although waterbird species richness did not change between the 1980s (110) and the 2000s (111), 13 species found in 1980s were replaced by 14 newly recorded species. Moreover, there were more species with declining trends (58) than with increasing trends (19). The population trends of species were affected by residential status and habitat types. Transients, wintering migrants, and habitat specialists were more likely to show declining trends compared to those breeding at Dongtan (including year-round and summer residents) and habitat generalists. Furthermore, species associated mainly with natural wetlands were more likely to decline than those associated mainly with artificial wetlands. These patterns suggest that the loss and change of wetland habitats at Chongming Dongtan adversely affected local population dynamics and might have contributed to the global decline of some waterbird species. Because Chongming Dongtan provides stopover and wintering habitats for many migratory waterbirds, protection and restoration of natural wetlands at Chongming Dongtan are urgently needed.  相似文献   
286.
Samuele Furfari 《Ambio》2016,45(1):63-77
The transport sector is fundamental for the economy but also for personal life. With a growing population and the globalization process, it is not surprising that the demand of transport is set to grow in the near future and certainly until 2050. This paper focuses on the huge potential of progress in the sector of technology for transport. As the principal sector for transport will remain on roads, the paper emphasizes the progress in the automotive sector. Since car manufacturers are investing massively into research and technology development to offer ever more efficient cars—not only energy efficient but also efficient in terms of safety and comfort—the car of tomorrow will be very different from the present one. The increasing role of electronics in cars will synergistically cooperate with that of so-called smart cities. The potential development of methane in the transport sector, mainly used for heavy transportation is discussed.  相似文献   
287.
提出"区域开发规模扩张的资源环境响应"的概念,并构建了区域开发规模扩张的资源环境响应指数、响应度模型及评价指标体系,通过定量分析1995-2008年东北地区开发规模扩张的资源环境响应变化及影响因素,得出以下结论:1995年以来东北地区开发规模不断扩大,而资源环境水平总体呈现出"先升后降"的波动变化态势。资源环境对东北地区开发规模扩张具有由"正响应"向"负响应"转变的特征,与此相对应,区域开发规模扩张对资源环境的影响程度也呈现出由"弱促进"向"强胁迫"变化的态势,这说明近年来在东北地区开发规模加速扩展的同时,其对区域资源环境造成的压力也日益增大。1995-2008年由经济快速增长导致的资源环境压力增长是引致东北地区开发规模扩张对资源环境影响由"正向促进"向"负向胁迫"转化的重要内部因素,而区域投资的不断增长以及工业的快速发展是东北地区开发规模扩张对资源环境影响由"弱促进"向"强胁迫"变化的主要因素。  相似文献   
288.
The relation between human population growth and land use change is much debated. Here we present a case study from Papua New Guinea where the population has increased from 2.3 million in 1975 to 5.2 million in 2000. Since 85% of the population relies on subsistence agriculture, population growth affects agricultural land use. We assessed land use change in the Morobe province (33,933 km2) using topographic maps of 1975 and Landsat TM images of 1990 and 2000. Between 1975 and 2000, agricultural land use increased by 58% and population grew by 99%. Most new agricultural land was taken from primary forest and the forest area decreased from 9.8 ha person(-1) in 1975 to 4.4 ha person(-1) in 2000. Total population change and total land use change were strongly correlated. Most of the agricultural land use change occurred on Inceptisols in areas with high rainfall (>2500 mm year(-1)) on moderate to very steep slopes (10-56%). Agricultural land use changes in logged-over areas were in the vicinity of populated places (villages), and in close proximity to road access. There was considerable variation between the districts but districts with higher population growth also had larger increases in agricultural areas. It is concluded that in the absence of improved farming systems the current trend of increased agriculture with rapid population growth is likely to continue.  相似文献   
289.
The 11th report of COMARE (Committee on Medical Aspects of Radiation in the Environment) established that the incidence of some childhood cancers, including leukaemia, is inversely related to population density in England, Wales and Scotland, and is particularly high in Buckinghamshire. Using a photographic archive survey, the present paper notes that population density is also inversely related to overhead wire domestic electricity supply in Buckinghamshire. Factors associated with domestic electricity supply may be relevant to the geographical distribution of some childhood cancers.  相似文献   
290.
Agricultural landscapes illustrate the impact of human actions on physical settings, and differential human pressures cause these landscapes to change with time. Our study explored changes in the terraced landscapes of Nisyros Island, Greece, focusing on the socioeconomic aspects during two time periods using field data, cadastral research, local documents, and published literature, as well as surveys of the islanders. Population increases during the late 19th to early 20th centuries marked a significant escalation of terrace and dry stone wall construction, which facilitated cultivation on 58.4% of the island. By the mid-20th century, the economic collapse of agricultural activities and consequent emigration caused the abandonment of cultivated land and traditional management practices, dramatically reducing farm and field numbers. Terrace abandonment continued in recent decades, with increased livestock grazing becoming the main land management tool; as a result, both farm and pasture sizes increased. Neglect and changing land use has led to deterioration and destruction of many terraces on the island. We discuss the socioeconomic and political backgrounds responsible for the land-use change before World War II (annexation of Nisyros Island by the Ottoman Empire, Italy, and Greece; overseas migration opportunities; and world transportation changes) and after the war (social changes in peasant societies; worldwide changes in agricultural production practices). The adverse landscape changes documented for Nisyros Island appear to be inevitable for modern Mediterranean rural societies, including those on other islands in this region. The island’s unique terraced landscapes may qualify Nisyros to become an archive or repository of old agricultural management techniques to be used by future generations and a living resource for sustainable management.  相似文献   
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