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1.
Samples of larval and juvenile fishes were collected at two depths weekly during spring and summer 1983 near the mouths of backwater areas in Pool 13 of the Upper Mississippi River. The study was conducted to determine the relative value of these habitats as nursery areas for fishes present and to note any interactions that might occur between the backwaters which are being rapidly lost to siltation, and the main channel. The larvae and juveniles collected represented 13 families divided into 27 lower taxa. Cyprinidae, Clupeidae, and Sciaenidae made up 90% of the total catch. Both larvae and juveniles were more abundant near the surface than near the bottom. Densities differed greatly among the three backwater areas studied. Larval fishes were grouped on the basis of their relative abundance in the backwaters or main channel. Overall, more larvae were captured in the backwaters than in main-channel habitats, indicating that backwaters were more productive. In the main channel, densities were greater downstream from the mouths of the backwaters than upstream-possibly indicating that (1) larval fish drifted out of the backwater areas, (2) water rich in nutrients or zooplankton that flowed into the main channel created productive downstream sites that were used as nursery areas, or (3) adult fishes selected downstream sites as spawning areas. Juvenile forms were more abundant in the backwater areas then in the main-channel habitats, some bottom-dwelling fishes excepted. The backwater areas were judged to be important nursery areas for larval and juvenile fishes, and seemed to benefit downstream main-channel sites. Any loss of these habitats would be detrimental to the Mississippi River as a whole.  相似文献   

2.
蒋志刚 《生物多样性》2018,26(7):775-100
中国正在开展一场以国家公园为龙头的保护地建设, 面临着一个跨领域、跨行业、全空间的保护地分类管理难题。世界各国建立了各种各样的保护地, 这些保护地存在着“同物异名、同名异物、一物多名”现象。IUCN提出了一个保护地分类系统, 以期将所有的保护地纳入一个体系。人们试图按照IUCN的保护地分类系统对现有保护地分类, 但是IUCN保护地分类系统的定义模糊, 无量化标准, 而保护地的属性常常存在非唯一属性等问题。保护地分类是一个学术问题, 可以自由探讨, 百家争鸣; 而保护地的管理是行政问题, 必须有章可依, 有法可循。中国现有10多种不同的保护地类型, 本身就是一种分类体系, 有的保护地, 如自然保护区、风景名胜区、地质公园等已经有相应的行政法规和管理经验。中国国家公园应整合优化而不是取代现有的其他类型保护地。以国家公园为龙头的中国保护地体系需要顶层设计和专门立法。保护地应当推动当地社区人与自然协调发展。  相似文献   

3.
Arid and semi-arid areas occupy an increasing fraction of the Earth's surface. Legume floras exist for most of these areas, but there is little information as to whether the plants nodulate and fix nitrogen (N) in their native habitats, although many have been used over millennia for food, forage and medicinal and other uses.

This review shows that, in those arid and semi-arid areas where data are available, the ability of legumes to nodulate is a significant attribute. It examines some host genera present and, where known, the bacteria that induce nodulation in them.

With some exceptions all legumes from well-studied arid areas have the potential to nodulate. Semi-arid areas vary between continents in terms of legume genera present, the probable extent of N fixation and in the endosymbionts (rhizobia) that induce nodulation in them.

With climate change and an increasing world population, there is an urgent need to develop the diverse range of nodulated legumes native to dry environments. With modern methods this goal is readily achievable.  相似文献   

4.
In recent years, the progressive decline in populations of anuran amphibians has left many species increasingly vulnerable to extinction. The potential role of morphological abnormalities as a mechanism of this decline has attracted attention in many recent studies. We investigated the occurrence and frequency of morphological abnormalities in anurans from northern of the state of Rio Grande do Sul, Brazil. We sampled 1674 individuals from three different environments – forest, farmland and peri‐urban areas – between 2001 and 2017. We recorded 89 individuals with morphological abnormalities, with 12 different types of abnormality in 19 anuran species. We recorded nine types of abnormality in forest and seven in the farmland, with brachydactyly being the most common abnormality in both areas. Only three abnormalities were recorded in the peri‐urban area, and all three were equally frequent. Studies of morphological alterations provide important insights into the potential effects of environmental impacts on anuran populations and may be essential for the planning of effective conservation strategies.  相似文献   

5.
希望在山区     
人们都在思考、议论、探讨我国农业面临的严峻形势和出路问题。人口在继续增长,耕地在继续减少,而耕地的后备资源又非常有限;水资源不足,发展水田和水浇地受到很大限制。城市闹水荒,又将进一步影响农业用水,这已是世界上最为突出的问题。仅靠耕地来解决人民生活和经济建设需要是困难的,使八亿农民富裕起来,难度就更大,这是勿庸置疑的。十三大政治报告指出,我国农村还处在开发时期,许多资源还没有合理利用,潜力很大,农林牧副渔各业和乡镇企业的发展前景都是十分广阔的。但如何开发,又如何利用很大的潜力来解决严峻的农业形势,对这些问题应认真作具体分析和探讨。  相似文献   

6.
Largely triggered by the Bali debate, conservation literature over the last decade has seen increasing realization of man's responsibility in ensuring survival of the world's protected areas. In African terms, there has been an overwhelming number of pilot projects which have the people label. Whereas this trend has been ecouraging, the overall conservation picture has not been very bright as the wildlife resources have continued to dwindle under surmounting human pressure. The problem does not seem to be awareness of the necessity for protected areas any more but rather whether it is feasible under the present prevailing circumstances.  相似文献   

7.
优先保护区识别对受威胁物种的多样性保护具有重要价值。基于GIS空间分析、管理及预测能力,以中国受威胁陆栖哺乳动物为对象,建立受威胁物种的分布二值网格系统;利用Dobson算法对研究区3810个网格单元进行筛除,确定全国范围下受威胁物种的优先保护区域;结合中国主要的自然保护地分布数据(国家公园和自然保护区),采用保护空缺方法分析优先保护区内受威胁动物的保护现状。研究发现,29个50km×50km的网格单元就包含了全部的受威胁陆栖哺乳物种,其中位于喜马拉雅山东南区等地的10个网格区域覆盖有80%以上的物种,其所处的10组县级行政区内被主要自然保护地保护的土地面积占25.9%,物种数占83.6%,存在一定的保护空缺。本文采用Dobson排除算法,以小面积规则网格为基本单元,顾及到了实验结果的客观性,有助于提高优先保护区的识别效率。  相似文献   

8.
Aim  To highlight and examine apparent paradoxes in assessing the effectiveness of different forms of land-use for biodiversity conservation.
Location  Tanzania.
Methods  We compare and contrast the findings of two recent and seemingly conflicting studies on the effectiveness of conservation protection strategies in Tanzania. We evaluate these studies in the context of a wider body of evidence relating to the problem of determining protected area performance.
Results  We highlight the importance of landscape-scale management approaches for biodiversity conservation; establishing clear management and monitoring objectives in advance; the interrelation between the choice of target species and the appropriate spatial scale over which to measure their fate; and differences between snapshot and longitudinal scales in assessing the effectiveness of conservation strategies.
Main conclusions  Protected area assessments should not promote an isolated focus on particular conservation targets or methods of monitoring and evaluating the effectiveness of conservation strategies. Instead we argue for a more pluralistic approach to evaluating conservation performance that can help to reveal where potential synergies in tackling different objectives exist, and clarifying the trade-offs when they do not.  相似文献   

9.
水獭是水生生态系统重要的指示种和旗舰种, 由于强烈的人为干扰, 中国的水獭种群数量大幅下降, 部分区域已局部灭绝。然而目前国内对水獭的调查和研究非常有限, 本底不清的状况已经严重影响到水獭的野外保育工作。本文以东北地区的欧亚水獭指名亚种(Lutra lutra lutra)为研究对象, 基于2016-2020年的调查数据, 使用组合建模的方法评估了水獭的潜在分布区; 利用地理信息系统和系统保护规划软件分析了水獭的保护优先区并计算了各省级行政区内水獭潜在分布区和保护优先区面临的人类压力; 结合国家级自然保护区的空间布局分析了水獭的保护现状, 并以内蒙古森工集团、大兴安岭林业集团、伊春森工集团三大国有林区为例分析了重点国有林区在水獭保护中的作用。结果表明: (1)水獭潜在分布区和保护优先区面积分别为104,515.04 km2和45,448.99 km2, 其中大兴安岭的水獭保护优先区集中连片, 并与小兴安岭的保护优先区相连, 栖息地之间没有明显地理隔离, 是维持东北地区水獭种群稳定的重中之重; (2)水獭面临的人类压力大小依次为: 辽宁 > 吉林 > 黑龙江 > 内蒙古; (3)研究区内110个国家级自然保护区中有63个包含水獭潜在分布区, 覆盖面积为12,168.93 km2, 仅占水獭潜在分布区面积的11.64%, 其中32个国家级自然保护区包含水獭保护优先区, 占水獭保护优先区面积的10.88%; (4)三大国有林区涵盖了71.18%的水獭潜在分布区和79.26%的保护优先区(面积分别为74,390.89 km2和36,022.22 km2)。由此可见, 尽管水獭潜在分布区中国家级自然保护区占比较低, 但是在天然林全面禁伐的背景下, 重点国有林区可能在未来东北地区的生物多样性保护中发挥更大作用, 因此我们建议将重点国有林区中具有重要保护价值的区域逐步纳入以国家公园为主体的自然保护地体系中, 以实现生物多样性的系统性和完整性保护。最后, 本文结合研究结果和实地调研提出以下保护建议: (1)加强对河流污染物的管理; (2)控制渔民捕鱼强度; (3)开展全面的水獭专项调查并建立长期的监测体系; (4)加大对水獭的科研投入; (5)加强宣传力度, 提升公众保护意识。  相似文献   

10.
The Mexican Government decreed Chinchorro Bank reef as a Biosphere Reserve in 1996. The aim of this study was to evaluate the spatial and size-frequency distribution of Acropora spp. in order to provide further knowledge and tools to enhance management. A field survey was conducted, within six regions, to locate and measure Acropora patches in the reef lagoon. Density, colony size and living tissue cover of Acropora colonies were evaluated using the line-intercept transect technique, combining direct observations and video transects. The results showed that Acropora spp. was preferentially distributed in the southern regions; where cover and density were high. Based on these results and considering that Acropora spp. produces landscape heterogeneity, which in turn generates shelter for other species, including some of considerable economic importance, then at least the South East region should be considered as a key area for Acropora species conservation, and should be included in the Chinchorro Bank management plan.  相似文献   

11.
Migratory water birds, including the Mallard (Anas platyrhynchos) – one of the most abundant waterfowl species – are involved in the dispersal of microfungi. This study was undertaken to collect data on the possible differences in fungal biota between mallards in urban and non-urban areas. In total, 53 species of microfungi were found in samples taken from the bill cavity and the cloaca. Among them, 19% are pathogens of humans, including the most common fungus, Candida albicans (18.0% of all isolates). Mallards living in proximity to humans were colonised with a higher number of fungal species than were birds living in non-urban areas. This might be the result of conditions that are favourable for microfungi in cities. The differences between the urban and non-urban environments are responsible for the higher levels of similarity in the species structure of the fungi found in the bill cavity and the cloaca within the same environment rather than in the same ontocenoses from different sites.  相似文献   

12.
为了探讨抗-HCV检测设置灰区的意义。以阈值定为阴性对照加0.12,灰区定为阈值下20%的范围,落在灰区内的样本用同一试剂双孔复查,只要有一孔阳性则判为阳性。结果显示,27份样本中,经复查有4份阳性,占14.8%,13份仍落在灰区,占48.1%,10份为阴性,占37%。如果不设灰区,将有抗-HCV阳性的样本的血液流入到患者体内,可危及患者的身体健康。  相似文献   

13.
Ingestion of ammonium induces hyperammonemia which increases tubulin content in cerebrum but not in cerebellum. We have dissected 11 discrete areas of cerebrum and quantified the tubulin content in control and hyperammonemic rats. An heterogeneity in the induction of tubulin is shown. The areas more affected are ventral hippocampus, dorsal hippocampus, hypothalamus, septum, reticular formation and frontal cortex, in which tubulin content increased by 63%, 27%, 32%, 48%, 45%, and 25%, respectively, after two months of feeding the ammonium diet.  相似文献   

14.
农药对农区生物多样性的影响   总被引:37,自引:13,他引:37  
农药的大量使用,已造成了许多生态环境问题,其中对生物多样性的影响尤为重要.农药的不合理使用,对生物群落的结构与功能产生了严重影响,降低了生物多样性.从昆虫群落结构、土壤中无脊椎动物种群数量、微生物区系和植物群落等方面论述了农药对农业区域生物多样性的影响,并提出了合理使用农药。保护农业区域生物多样性的具体措施.  相似文献   

15.
Analyses of gaps in protected area (PA) coverage of species distributions have been carried out extensively for the past two decades, aiming to better locate new PAs and conserve species. In this study, progress to close gaps in the protection of the Important Bird Areas (IBAs) of Tanzania is assessed between 2002 and 2009, with a detailed GIS analysis from 2007 to 2009. Remaining gaps are ranked according to biological factors such as numbers of red list and restricted range avian species and social pressures such as human population, agriculture and density of the road network. Results show that there has been a 5.3% increase (7615.1 km2) in protection of IBAs between 2007 and 2009. Of the 27 remaining IBA protection gaps, three are of high, nine of medium and fifteen of low priority for action. The current IBA ‘gap area’ of 17,133.3 km2 contains around 26% forest, 13% shrubland, 9% grassland, 36% wetland and 12% agricultural land. This analysis provides a simple template for defining where further action to protect remaining IBA sites in Tanzania would lead to enhanced conservation of avian biodiversity in that country and provides a methodology for analysis leading to conservation action elsewhere in Africa.  相似文献   

16.
Bolivia is a megadiverse country. A large part of its biodiversity is due to the fact that in its territory different biogeographical regions meet. As a preliminary means to understand how this biodiversity is being protected, three previous studies undertook an evaluation of how well represented the ecological regions were in the National System of Protected Areas (NSPA). However, the most recent biogeographical findings in Bolivia call for a new analysis of this sort. We try to achieve this, emphasizing the situation in the Andean dry regions, which have been given scarce priority, despite their high biological value. In general, xeric ecoregions are under-represented while humid ones are over-represented. The Prepuna and the central altiplano (which includes the Dry Puna sub-ecoregion) are not represented within the NSPA, nor is the Beni Cerrado sub-ecoregion. The Inter-Andean Dry Valleys cover only ca. 0.5% of the protected area, in spite of their diverse flora and status as one of Bolivia’s most important centers or endemism. Although the diverse Chiquitos Dry Forest is well represented, it is protected mostly as an ‘Integrated Management Natural Area’, and thus lacks full protection. The Semi-Humid Puna and the Flooded Savannas of the Moxos Plains, important subdivisions of two main ecoregions, are markedly under-represented in the NSPA, despite the importance of Moxos plains as a center of endemism for birds. Other ecoregions have a representation in the NSPA which can be considered adequate or even excessive. The over-representation of the humid Yungas mountain forests seems to be justified as this is probably Bolivia’s most important center of diversity and endemism. There is a need for a more proper distribution of some protected areas which consider true limits, size, diversity, endemism and other attributes of the different ecoregions in a more rigorous manner.  相似文献   

17.
This study aimed to establish if the Lower Río de la Plata Basin (LRPB) wetlands can be considered a biogeographic unit. The species of this area were compiled and segregated according to the habitat, selecting only 87 endemic taxa restricted to the LRPB and linked to wetlands. Distributional data of species obtained from the literature, web databases, biological collections, and field trips were georeferenced. The areas of endemism were established as those areas where the distribution of two or more taxa overlaps in groups of rivers’ sections with geographic continuity and were tested with a cluster analysis. This congruence is due to ecological, geomorphological, and historical factors. Four areas of endemism were found: a broad area that comprises the whole study area (Riverine district), which is divided into three nested smaller areas (Paraguay–Paraná Flooding Valleys, Uruguay Basin, and Paraná Delta subdistricts). Then, we analysed 170 taxa distributions to evaluate the relationship between the study area and the neighbouring biogeographic units. According to the results, the study area belongs to the Paraná biogeographic province. Some areas of endemism are hidden inside broader areas and are hardly detected with the currently used biogeographic grid-methods. We propose to combine the information about ecological requirements of each taxon with its georeferenced records to estimate their areas of distribution as a primary step for searching areas of endemism in intracontinental studies.  相似文献   

18.
19.
人口的增长和自然资源的有限性决定了很难把更多的土地用于生物多样性的保护。通过BMAS(生物多样性管理面积选取)模型与GIS(地理信息系统)的结合,可以用尽可能少的土地资源实现一定水平的生物多样性的保护。该方法初步在西双版纳的勐拉县进行了应用。与现实自然保护区面积的对比,用模型选区自然保护区有显著效果。该方法在保护与发展矛盾尖锐的发展中国家非常适用。  相似文献   

20.
Protected areas in the Congo Basin cover approximately 6% of the landscape, and several international NGOs are proposing substantial additions to the present network of parks and reserves. Yet, chronic under-funding has long precluded effective management of most parks and reserves resulting in their progressive ecological impoverishment, and the loss of biodiversity. Furthermore, not only are the indebted nations of the Congo Basin not in a position to contribute significantly to cover the recurring costs of protected area management, the growing opportunity costs of setting aside protected areas is increasing the incentives to local communities and national governments to 'illegally' exploit economically valuable resources within parks and reserves. If the global value of the biodiversity contained within the Congo Basin is considered worth preserving then donors and international NGOs must work with national governments to reach consensus on an optimal protected area network that (a) contains a representative assemblage of forest species; (b) is composed of forest blocks that are sufficiently large, intact, and likely to persist; (c) contains zones of active speciation (e.g. ecotones), and (d) can expect to receive sufficient long-term financial support to ensure effective management. Given the 'need to eat today' reality of economies in the Congo Basin, the international community must decide to shoulder most of the costs of conservation of globally important biodiversity. If donors continue to under-finance protected areas rather than make the hard choices associated with prioritizing protected area spending then most if not all protected areas within the Congo Basin will continue to exhibit reductions in the biomass of individual species, and risk the extirpation or extinction of large, slow reproducing species, and rare endemics.  相似文献   

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