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1.
We summarized the status of wolves (Canis lupus), elk (Cervis elaphus), and woody browse conditions during the 20th century for the upper Gallatin elk winter range in southwestern Montana, USA. During this period, wolves were present until about the mid-1920s, absent for seven decades, and then returned to the basin in 1996. A chronosequence of photographs, historical reports, and studies indicated willows (Salix spp.) along streams became heavily browsed and eventually suppressed following the removal of wolves, apparently due to unimpeded browsing by elk. However, after wolf establishment in 1996, browsing intensity on willows lessened in some areas and we hypothesized that, at both a landscape and fine scale, browsing pressure reflects terrain configurations influencing predation risk (nonlethal effects), in conjunction with lower elk densities (lethal effects). We measured browsing intensity and heights of Booth willow (S. boothii) along 3000 m reaches of the Gallatin River and a tributary to examine the potential influence of wolf/elk interactions upon willow growth. Where the Gallatin Valley is relatively narrow (high predation risk), willows began releasing in 1999 and by 2002 were relatively tall (150–250 cm). In contrast, willow heights along a wider portion of the Gallatin Valley, along the open landscape of the tributary, and an upland site (all low predation risk) generally remained low (<80 cm). We identified terrain and other features that may contribute to the perceived risk of wolf predation, by elk for a given site. Although alternative mechanisms are discussed, changes in willow communities over time following wolf removal and their subsequent reintroduction were consistent with a top-down trophic cascade model involving nonlethal and possibly lethal effects. If similar top-down effects upon vegetation hold true in other regions of North America and other parts of the world where wolves have been extirpated, wolf recovery may represent a management option for helping to restore riparian plant communities and conserve biodiversity. 相似文献
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Food habits of the grassland wolf in Inner Mongolia of China 总被引：3，自引：0，他引：3
IntroductionThettnIf(CanishII,us)belongstoCan1ivora.Tllcwolfdistributedinll1ncrMol1goliaisaCl1incscstIbspccics(CanishII,llscl;ancoGray).Tl1ctvoIfllasagrcatcco-logicaladaptingcapacity.Itisaln1ostdistributcdovcrtvholcCIlina.Inso111careas,tl1cwolfoftcl1doesahan11tosol11cdolllesticani1nals.TocOI1troltvolfPopuIatio11,pcoplcalwaysl11a1mgetokilltl1ettolvcs.Il1sol11crcgiOI1s,tlloscwllokilltllewolvcsarcevcnrcttardcd.n1us-cxactrolcoftlletvolfintl1cccologicalsystcl1lsI1ouldbccIarificdfortllcpr… 相似文献
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Predation risk is an important factor influencing the distribution of ungulates and their impact on forest structure. However, simultaneous predation risk by wolves and humans is rarely considered in the analyses of habitat selection by ungulates. We counted ungulate pellets on transects to analyse the influence of wolves and humans on ungulate density distribution in the Białowieża Forest, Poland. We assessed whether (1) forest exploitation influenced ungulate habitat selection, (2) ungulate density was higher in areas without human hunting, (3) ungulates avoided the surroundings of a major road, (4) prey density was higher in the strife zone between home ranges of wolf packs both in the presence and absence of human hunting, (5) ungulates avoided areas selected by wolves, and (6) wolf kill sites were in high prey density areas. Red deer (Cervus elaphus) and wild boar (Sus scrofa) selected unexploited over exploited forests and areas without hunting, whereas roe deer (Capreolus capreolus) preferred exploited forests. Wild boar and European bison (Bison bonasus) avoided the area within 300 m of a major road, whereas we could not detect any avoidance by red or roe deer. Prey density was not higher in wolf strife zones, regardless of human hunting. Ungulates did not avoid areas selected by wolves. Wolves killed red deer in areas with prey density of about 4 red deer/km2, regardless of whether the average red deer density in those areas was higher or lower. We conclude that habitat alteration by forest exploitation and hunting by humans influenced the density distribution of ungulates more than predation risk by wolves. 相似文献
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中国退耕还林发展阶段研究 总被引：13，自引：0，他引：13
研究表明,中国退耕还林进程可划分为4个阶段:号召动员阶段、试点示范阶段、工程建设阶段、后期巩固阶段。文中论述了每个阶段的主要标志、重点内容、基本特点和目标效果。 相似文献
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本文综述了世界各国引种湿地松及其人工林经营的概况,总结了近十多年来人工林发展缓慢的原因,探讨分析了我国已出现或将面临的一些问题,并提出相应的对策。 相似文献
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Olfactory receptors(ORs),the first dedicated molecules with which odorants physically interact to arouse an olfactory sensation,constitute the largest gene family in vertebrates.Dogs and wolves,like many other mammals,have a highly developed capability to detect and identify odorant molecules,even at minimum concentrations.In this study,the olfactory receptor repertoire from domestic dog and its closest relative,the wolf,were sequenced to estimate the fraction of pseudogenes in each subspecies.The fraction of disrupted olfactory receptor genes in dog was 17.78%,whereas,that in wolf was 12.08%.As expected the dog was less dependent on olfaction than the wolf,and the dog had more olfactory receptor pseudogenes.However,the observed difference between the two subspecies was not at the significant level(χ2 = 1.388,p = 0.239 > 0.05).The values indicated that although domestication might play a role in the reduction of OR genes,it could not be concluded that the living environment provided by domestication lead to a significant reduction of the functional olfactory receptor repertoire.Furthermore,the purpose of domestication may also have influence on the ratio of functional olfactory receptor genes reduction. 相似文献
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After an absence of approximately 70 years, gray wolves (Canis lupus) were re-introduced into Yellowstone National Park in the mid-1990s. We studied the potential influence of wolf/ungulate interactions upon willow (Salix spp.) growth in the valleys of the Gallatin and Lamar Rivers, as well as Slough and Soda Butte Creeks, in the northern Yellowstone ecosystem. When we compared willow heights from photographs taken prior to 1998 (willows <2 m tall) with those taken in 2004, we found an increase in willow height for 22 of 42 sites within the study area. Based on comparisons of the chronosequence photos, since wolf introduction none of the 16 upland riparian sites showed an increase in willow height, while 22 of 26 of the valley-bottom riparian sites had willow height increases. In 2004, willow height exhibited a strong inverse relationship with the percentage of browsed stems (r = −0.81, p < 0.01, n = 42). Results of regressions for valley-bottom sites indicated that view distance, impediment distance, and the number of bison (Bison bison) flops were inversely related to willow height (p ≤ 0.02). Increased willow heights were not significantly (p = 0.18) related to patterns of moisture availability. Willow height increases documented in this study appear to have been at least partially due to behaviorally mediated trophic cascades involving wolves and ungulates, via a mechanism of predation risk. While willow release (i.e., increased height growth) within the study area is in a very early stage, results suggest potentially important indirect effects of a top carnivore in a terrestrial food chain that may aid in the restoration of riparian species and the preservation of biodiversity. 相似文献
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鸟类环志是研究侯马迁徙最简单有效的方法,已广泛被世界各国所采用,并发挥了巨大作用。文章介绍了欧美和日本等国的研究现状,以及我国鸟环工作的进展和存在问题。 相似文献
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亚洲主要国家竹种资源与利用 总被引：5，自引：4，他引：1
亚洲是世界竹子的主要分布区，竹林培育和加工利用历史最为悠久，竹种资源、竹林面积和竹产业产值均位居全球首位。亚洲竹资源主要分布在东亚、东南亚和南亚国家，在中亚、西亚和北亚国家少有分布。以中国为代表的东亚国家竹种丰富，竹产业发达；以越南、马来西亚为代表的东南亚国家竹产业发展迅速；以印度为代表的南亚国家竹林面积最大，竹产业欠发达。文章分析了亚洲具有代表性的17个国家的竹资源及利用现状，以期为加强亚洲各国竹产业合作、推动区域竹产业高质量发展提供参考。 相似文献
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枸杞属（Lycium L.）物种在全球分布广泛,资源丰富,是枸杞产业可持续发展的重要物质基础。文中综述了我国枸杞的栽培历史、应用价值,以及国内外枸杞属物种资源的分布、种类、研究进展和成果,分析了我国在枸杞种质资源研究利用中存在的问题并提出发展对策,旨在为我国枸杞育种工作和物种资源的收集、保存、研究、应用提供参考。 相似文献
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竹亚科（Bambusoideae）刚竹属（Phyllostachys Sieb.et Zucc.）是竹类植物中环境适应性最强、分布范围最广、也是物种多样性较为丰富的一个类群。由于其经济、生态和社会价值均十分突出,且许多种类具有较强的功能性和耐低温属性,历史上一直都被世界各国的园艺师们争相引种、培育、并被广泛栽培和应用,因而涌现出数量庞大的栽培品种类群。全世界的刚竹属植物约60余种,且分布于世界各地的刚竹属植物,大多是从中国引入。依据国际上业已公布的权威资料和《国际栽培植物命名法规》（ICNCP）的规则和要求,经系统整理,目前全世界可认定为刚竹属栽培品种的竹类植物有127个（不包括原栽培品种）,分属于27个不同竹种。此外,还有21个栽培品种无法确认,有待进一步考证。 相似文献
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我国麻疯树地理种源及分布区考证 总被引：2，自引：0，他引：2
经过详细地调查研究证明,我国滇、川、黔三省的热带和亚热带干热河谷区存在大量麻疯树天然群落和野生种群,并对其进行了植物形态学、生长生物学、群落生态学、种群生态学和分布区学的全面研究和再认识,提供了丰富和确切的观察结果。在上述研究基础上,进一步提出了"雨林型"麻疯树地理种源和"萨王纳型"麻疯树地理种源的新概念,为我国麻疯树产业化种植及分区规划提供了依据。金沙江干热河谷"萨王纳型"麻疯树地理种源的存在和出现展示着该物种在纬度极限和海拔极限条件下的生存能力,充分证明其泛热带分布和广泛分布于热带亚洲、热带非洲和热带大洋洲的事实,为麻疯树植物区系地理学研究提供了佐证。 相似文献
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We report on the recent growth of upland aspen (Populus tremuloides Michx.) thickets in northwestern Yellowstone National Park, USA following wolf (Canis lupus L.) reintroduction in 1995. We compared aspen growth patterns in an area burned by the 1988 fires to aspen growth patterns in an adjacent unburned area. Elk (Cervus elaphus L.) are the principal ungulates that use this area to meet foraging needs. Within a 2 m × 6 m belt transect established in each aspen thicket, we measured aspen densities and recorded annual browsing and height information on the three tallest post-1988 aspen stems. We found greater densities (p < 0.01) in the burned area relative to the unburned area. A decline in the percentage of stems browsed in the burned area began in 1997, with no measured browsing occurring since 2001. In contrast, the percentage of stems browsed in the unburned area began declining in 2002, with 41% of stems still being browsed in 2004. We hypothesize that the combined effect of fire and a subsequent decrease in herbivory following wolf reintroduction facilitated aspen growth. We further propose that, in addition to any changes in elk density in recent years, a recoupling of fire with increased predation risk from wolves may create a positive feedback loop that improves aspen recruitment. 相似文献
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北大港湿地自然保护区位于天津市东南部的大港区,本次调查高等植物共有174种,占天津植物区系的12.80%(天津市高等植物共1359种),其中野生植物153种,人工种植植物21种。该区域湿地植物区系特征明显,主要表现为:植物区系成分复杂多样;地理成分多样,植物区系联系广泛;优势种多、覆盖度大等等。同时,北大港湿地自然保护区地理成分复杂,属的分布以世界分布类型为主,其中世界分布属31属,占湿地总属数的23.67%,在所有属中所占比重为最高。此外,在本次北大港湿地植被调查过程中,发现了3个物种在2004版的《天津植物志》中未被收入,通过科考确认3物种在天津有分布。 相似文献
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亚洲象分布、数量、栖息地状况及种群管理 总被引：2，自引：1，他引：1
全世界野生亚洲象的数量约为5万只,分布于全球13个国家。亚洲象喜栖于热带雨林和季雨林地区,集中在各国气候湿润地带且多呈跨境分布。亚洲象适宜栖息地丧失和破碎化是各分布国面临的最主要问题之一,栖息地面积减少带来的亚洲象死亡、人象冲突等一系列生态经济问题凸显,各国就解决栖息地丧失与破碎化问题和缓解人象冲突问题提出了相关办法并拟定了共同行动方案。文中从亚洲象在世界各分布国的数量、栖息地丧失和破碎化程度的现状、人象冲突问题及各国针对保护亚洲象正在和将要计划实施的种群管理措施等方面介绍亚洲象相关信息,以期为科学管理和保护亚洲象种群提供详细的参考。 相似文献