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11.
A comparative analysis of the dynamics of insular populations of terrestrial animals was performed. The stability of insular populations and the relationship between their viability and the type of dynamics are discussed.  相似文献   
12.
In order to develop small islands, not only must a vital agricultural system be maintained, but the range of opportunities for tourism must be increased with respect to both the seaside and the environmental features of the rural landscape. As an alternative to the traditional and economically declining ones, many innovative production processes can be identified, but their success depends on their interaction with the physical, biological, economic and social environment. In order to identify the main nodes and the most critical interactions, so as to increase the probability of success of a new productive process, a methodological approach based on the science of complexity is proposed for the cultivation of capers (Capparis spinosa L.) on the island of Pantelleria. The methodology encompasses the identification of actors and factors involved. the quantitative evaluation of their interactions with the different stages of the productive process, and a quasiquantitative evaluation of the probability that the particular action will be performed successfully. The study of “traditional,” “modernized,” and “modernized-sustainable” processes, shows that the modernized-sustainable process offers mutually reinforcing opportunities in terms of an integrated development of high-quality agricultural products and the enhancement of environmental features, in conjunction with high-efficiency production techniques, in conjunction with high-efficiency production techniques, in a way that suits the development of Pantelleria. There is a high probability of failure, however, as a result of the large number of critical factors. Nevertheless, the present study indicates which activities will enhance the probability of successful innovation in the production process.  相似文献   
13.
Effects of Forest Fragmentation on a Dung Beetle Community in French Guiana   总被引:4,自引:0,他引:4  
Abstract:  Fragmentation is the most common disturbance induced by humans in tropical forests. Some insect groups are particularly suitable for studying the effects of fragmentation on animal communities because they are taxonomically and ecologically homogenous. We investigated the effects of forest fragmentation on a dung beetle species community in the forest archipelago created in 1994–1995 by the dam of Petit Saut, French Guiana. We set and baited an equal number of pitfall traps for dung beetles on three mainland sites and seven island sites. The sites ranged from 1.1 to 38 ha. In 250 trap days, we captured 50 species in 19 genera. Diversity indices were high (2.18–4.06). The lowest diversity was on the small islands and one mainland site. Species richness and abundance were positively related to fragment area but not to distance from mainland or distance to the larger island. The islands had lower species richness and population than mainland forest, but rarefied species richness was relatively invariant across sites. There was a marked change in species composition with decreasing fragment that was not caused by the presence of a common fauna of disturbed-area species on islands. Small islands differed from larger islands, which did not differ significantly from mainland sites. Partial correlation analyses suggested that species richness and abundance of dung beetle species were positively related to the number of species of nonflying mammals and the density index of howler monkeys ( Alouatta seniculus ), two parameters positively related to fragment area.  相似文献   
14.
通过对我国无人岛保护和开发现状及其开发模式演变趋势的分析 ,阐明生境更新的内涵和方法 ,提出 1种新型的保护性海岛开发模式 ,包括建设自然保护区 ,实施生态旅游 ,开发海洋牧场、港口等。按照保护性开发和生态恢复等原则 ,运用生境更新的原理和方法 ,将我国无人岛划分为生态型、开发型、居民迁出型及国防型 4种类型 ,以利于实行有效的分类管理。  相似文献   
15.
The biophysical features of small islands (SI) distinguish them from other territories; isolation, small size and several anthropogenic pressures reduce the resilience of ecosystems and increase their vulnerability to global changes. Many SI have a shortage of infrastructures, institutions and technical/financial resources that hinder planning and require different integrated solutions. In Portugal, the National Ecological Reserve (NER) is legally binding for spatial planning instruments. It aims to defend natural values and areas of ecological value, or sensibility, or susceptible to natural hazards. However, the criteria for the design of NER are strictly set for mainland territory, not taking into account specific features of small islands. A case study of the Azores Archipelago is used to demonstrate that spatial planning instruments should be adapted to island contexts. Such adaptation will increase the effectiveness of their implementation in relation to the protection of natural resources, stability of biophysical structures and prevention of natural hazards. Observing the main differences between mainland and the Azores Archipelago it is possible to define a methodological transposition of the NER aims and goals into an island context. This approach is an answer to the constraints in effective adaptation of spatial planning instruments for islands.  相似文献   
16.
An experiment on urban effects of warm season rainfall of a moderately sized city and its downwind towns found no evidence of global enhancement. However, there are grounds for believing that the intra urban distribution of precipitation is influenced by urban variables among which air pollution and urban roughness are considered primary. The presence of an urban heat island did not appear to improve rainfall. On the contrary, it appears to be a factor in the relative aridity of the downtown sector of the city.  相似文献   
17.
舟山群岛港口发展有广阔前景   总被引:2,自引:1,他引:1  
舟山海域位于长江水道和我国南北洋通道交汇的前沿,是我国南北海运的要冲与江海联运的枢纽,地理位置非常优越。舟山的三大优势资源“鱼、港、景”中,港的优势得天独厚拥有极为丰富的深水岩线,建设第四、五代大型集装箱泊位及其他大型深水泊位,发展潜能很大。舟山港域的发展提出了三点建议:1、充分利用区域优势,北依上海,南托宁波,定位于华东沿海重要的区域性洪口,成为长江三角洲口群体中的一个重要组成部分。2、利用岛屿  相似文献   
18.
南海岛礁环境下304不锈钢腐蚀行为分析   总被引:1,自引:1,他引:0       下载免费PDF全文
目的 研究304不锈钢材料在南海岛礁大气、飞溅、潮差和全浸区环境下暴露0.5 a的腐蚀行为与规律.方法 通过实海环境适应性试验,获取304不锈钢材料在南海岛礁环境下的腐蚀数据.通过腐蚀形貌观察,明确304不锈钢的主要腐蚀形式.通过电化学测试分析,评价304不锈钢耐蚀性能,阐明其腐蚀机理.结果 304不锈钢在南海岛礁环境下以点蚀为主,4个区带的平均腐蚀速率分别为0.8、1.1、1.3、3.2μm/a,平均点蚀深度分别为13.57、15.26、18.62、2.43μm,最大点蚀深度分别为28.85、35.63、32.93、40.25μm.交流阻抗和Mott-Schottky曲线测试结果显示,四个区带试样的电荷传递阻抗分别为1.27×107、8.76×106、7.35×105和5.76×105?·cm2,载流子含量分别为6.56×1022、1.01×1023、2.80×1023和4.15×1023 cm?3.在全浸环境下,304不锈钢钝化膜破损最严重,耐蚀性下降最大.结论 在大气区和飞溅区,304不锈钢以点蚀为主,并在固定部位伴随有轻微缝隙腐蚀;在潮差区和全浸区,由于钙镁沉积物和海生物附着,304不锈钢表面形成大量Cl?饱和、低溶解氧浓度的腐蚀微电池环境,发生了严重的局部腐蚀,且以全浸区最为严重.  相似文献   
19.
Abstract:   The Juan Fernandez Archipelago, a Chilean national park and biosphere reserve, is 700 km west of continental Chile. Invasive plant species pose major threats to the native, highly endemic vegetation, especially on Robinson Crusoe Island (Mas a Tierra), where there is a permanent settlement. We used historical and recent vegetation map data as well as recent vegetational point data to reconstruct vegetational changes on the island since the early twentieth century. In addition, we used logistic regression models with environmental variables or their surrogates (elevation, solar radiation, topographic similarity index, slope position) to estimate the potential distributions of the worst invaders. Native vegetation has been affected most severely by Acaena argentea , Aristotelia chilensis , Rubus ulmifolius , and Ugni molinae , leading to a significant decrease of endemic plants in the montane forests and native shrublands. The native forest has decreased by approximately one-third. The area affected by Aristotelia chilensis increased from 6.5% to 14% of the total island area. Ugni molinae , once rare, is now abundant (4.6%), as is Acaena (11.9%). Rubus ulmifolius , not present 80 years ago, now covers about 7% of the island's surface. The distributions of all studied species except Rubus ulmifolius are significantly ( p < 0.05) controlled by the environmental factors we examined. Inferring from potential distributions of Aristotelia chilensis and Ugni molinae , 50% of the native montane forest could be invaded or replaced (with a probability of >60%) by these plants. Based on the invasion speed of the past 80 years, this would take another 80 years if conservation measures do not succeed.  相似文献   
20.
万宁滨海与西沙群岛大气腐蚀性对比研究   总被引:4,自引:3,他引:1  
统计分析了西沙群岛和万宁试验站近海场的润湿时间、空气中二氧化硫和氯离子沉积速率,根据环境因素法和标准金属法评定了两地的大气腐蚀性,两地的大气腐蚀等级同为C5级,但西沙群岛的腐蚀性稍弱于万宁试验站近海场。Q235钢、镀镍钢、镀铬钢、不锈钢钝化件在两地的试验结果证实了上述结论,试验结果表明,万宁试验站近海场积累的大量试验数据可应用于西沙群岛。  相似文献   
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