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1.
《Biological conservation》1986,36(3):199-252
By reference to extensive vegetation surveys the habitats of common and rare herbaceous plants and small (<1 m) woody species have been compared for the Sheffield region of Central England.Common species are frequent at sites of high fertility, are strongly represented in habitats which are heavily disturbed or of recent origin and generally have a wide geographical and ecological range in the Sheffield region and within Britain as a whole.Many of the rare species are restricted to the lowland half of the region and most of the species which have become extinct from the region in the recent past were associated with lowland agricultural areas where the pressures of changing land use are greatest. Rare species are concentrated within less fertile sites, particularly those with calcareous soils, and they are often present in species-rich vegetation in ancient habitats. Many rare species have a narrow ecological range, some appear restricted to ‘intermediate’ habitats (either ecoclines or ecotones) and a high proportion are near the northern limit of their geographical range.No single ecological characteristic is totally diagnostic of either common or rare species. Most of the differences between common and rare species in the Sheffield region may be interpreted in terms of the availability of suitable habitats within the region with common species occupying common, and rare species less common, habitats.  相似文献   

2.
S. Salmon  J.F. Ponge 《Pedobiologia》2012,55(6):295-301
Although considerable work has been done investigating the factors that underlie species trait assemblages in emblematic groups such as plants and vertebrates, more remains to be done in belowground invertebrate species. For this group, in particular, relationships between species traits and habitat preferences are still a matter of debate. To eludicate upon the relationships, springtails were sampled in a heterogeneous landscape centered on the Sénart forest, near Paris (northern France), which represented the largest possible array of five environmental gradients (humus forms, vegetation, moisture, vertical strata, and seasons) over which Collembola are known to be distributed. The distance between samples varied from a few cm to several km. Canonical correspondence analysis using species (128) as observations and species trait attributes (30) and habitat indicators (82) as dependent and independent variables, respectively, allowed us to discern whether species habitats and species trait assemblages were related and which trends could be found in trait/environment relationships. It was concluded that, within the studied area, species habitats were significantly associated with species trait assemblages. The main gradient explaining the distribution of species traits combined the vertical distribution of habitats (from the mineral soil to plant aerial parts), and the openness of the environment, suggesting that a complex of many ecological factors is at play. For the ecological traits of Collembola, this gradient corresponded to an increasing contribution of sensory and locomotory organs, bright color patterns, size and sexual reproduction, all attributes associated with aboveground life under herbaceous cover. Another important, although secondary contrast concerned traits associated with habitats far from soil but that were concealed (corticolous vs. all other habitats). Soil acidity and water did not contribute significantly to trait distribution, at least within the limits of our database.  相似文献   

3.
为了给石羊河流域柽柳群落植被恢复与保护提供参考依据,以石羊河流域4种类生境型柽柳群落为研究对象,测定了群落物种组成、数量特征及土壤水分、盐分,分析了不同生境群落特征及其与土壤水分之间的关系。结果表明:(1)柽柳群落中共有植物22种,分属9科20属,其中灌木植物最多,为8种(5科6属),其次是多年生草本,为7种(4科7属),一年生草本为7种(3科7属),分别占总物种数的36.36%,31.82%,31.82%。(2)柽柳群落中,固定盐碱沙地密度最大,盐碱地和退耕湿地次之,丘间低地最低; 平均密度差异不显著(p>0.05); 盖度差异显著(p<0.05),以固定盐碱沙地最大,为73.33%,盐碱地和丘间低地次之,均为61.67%,退耕湿地最小,为47.00%。(3)不同生境类型柽柳群落在物种组成及多样性方面存在差异,从Margalef丰富度指数、Shanon-Wiener多样性指数、Simpson多样性指数和Alatulo均匀度指数看,丘间低地>盐碱地>固定盐碱沙地>退耕湿地(p<0.05),丘间低地群落优势度指数低于盐碱地和固定盐碱沙地、退耕湿地,群落结构相对稳定; 丘间低地Pielou均匀度指数明显高于其他3种类型。(4)在0—10 cm,10—20 cm,20—30 cm,30—40 cm,40—60 cm,60—80 cm土层范围内,盐减地和固定盐碱沙地土壤含水率最高,其次是退耕湿地和丘间低地,总体呈现出先升高然后逐渐下降的趋势。物种多样性与土壤水分均呈正相关关系,但均未达到显著水平(p<0.05),综上所述,不同生境柽柳群落组成物种稀少,结构简单,种群物种平均密度差异不显著。群落组成物种中,灌木种类最多,多年生和一年生草本种类相同。丘间低地多样性指数高于其他生境类型,退耕地最低,而生态优势度指数则相反,物种多样性与土壤水分表现出非显著的正相关关系。  相似文献   

4.
Cryptic species are similar in morphology, and make interesting subjects for relating morphological differentiation to ecological resource partitioning. Can species that are morphologically almost identical occupy different ecological niches, and hence potentially need distinct conservation planning? The discovery that the most widespread bat in Europe - the pipistrelle - comprised two cryptic species (Pipistrellus pipistrellus and Pipistrellus pygmaeus) that emit echolocation calls at different frequencies provides a remarkable model system for investigating links between morphology, echolocation call design and resource partitioning. We investigated resource partitioning between the two cryptic species of sympatric pipistrelle bats by radio tracking breeding females. Habitat selection was investigated by using compositional analysis. P. pygmaeus selected riparian habitats over all other habitat types in its core foraging areas, whereas P. pipistrellus, although preferring deciduous woodland overall, was more of a generalist, spreading its foraging time in a wider range of habitats. Although morphologically very similar, the cryptic species show quite different patterns of habitat use. Our findings suggest that large-scale differences in habitat preferences can occur between sympatric bat species that are virtually identical in flight morphology; hence morphological differences may be a weak indication of ecological differences between taxa. Conservation planning needs to take account of these differences to meet policy and legal obligations associated with these protected cryptic species.  相似文献   

5.
鲁中水土保持生态修复区种子植物区系特征   总被引:2,自引:0,他引:2       下载免费PDF全文
 为鲁中石质山地水土保持生态修复过程中适宜植物种类的选择、保护与合理经营提供理论依据,对淄川峨庄水土保持生态修复区内植物区系组成和地理成分进行分析。结果表明:1)该植物区系内共有种子植物271种,隶属于61科157属,分别占我国种子植物区系科、属、种的17.28%、4.90%和0.998%,其中单种科和极小科(含29种)所含的种数占总种数的91.6%,单种属和含2~4种的属有161个,占总属数的96.18%,可以看出该研究区内植物科和属的分布是比较均匀和丰富的;2)该区植物区系温带成分,特别是北温带成分具有明显优势,热带性质属在该区系中占有较大的比例,说明该地区植物区系与热带植物区系有较密切渊源,并具有一定的亚热带热带区系的过渡性;3)该区植物区系的特有性较低。  相似文献   

6.
Five main conclusions arise from this review of the responses of species to anthropogenic disturbance in Madagascar: First, species’ reactions to anthropogenic disturbance are generally negative, but remain poorly known. Our knowledge is patchy among and within higher taxonomic groups; we are still largely gathering case studies. Second, taxonomic groups vary considerably in which proximate factors are most important. Third, several groups show differing responses within different ecoregions. Whether these differences are consistent across groups requires further testing. Fourth, related species often have divergent reactions to disturbance, even within lower taxonomic groupings (families or genera). Thus, we cannot rely on phylogenetic relatedness or even ecological similarity to infer similarity in responses. Finally, disturbance typically reduces species diversity (especially of native and/or endemic species), but also causes species turnover, typically with forest specialists replaced by grassland generalists, and endemics replaced by non-endemics (including invasives). Given these knowledge gaps, we stress the urgency of applied studies that assess species’ ecology, behaviour and health across disturbance gradients, including purely anthropogenic landscapes. Remaining natural vegetation and protected areas will be unable to preserve Madagascar’s biodiversity under the impact of climatic change; we must understand responses of plants and animals to disturbance in order to create buffer zones and corridors combining secondary, degraded and natural habitats.  相似文献   

7.
Theoretical advances in systematic reserve design aim to promote the efficient use of limited conservation resources and to increase the likelihood that reserve networks enhance the persistence of valued species and ecosystems. However, these methods have rarely been applied to species that rely on spatially disjunct habitats. We used the marbled murrelet, a seabird that requires old-growth forest in which to nest and high quality marine habitats in which to forage, as a case study to explore methods of incorporating multiple ecological values into single species spatial reserve design. Specifically, we used the cost function in MARXAN to include the ecological value of marine habitats while identifying spatial solutions for terrestrial nesting habitat reserves. Including marine values influenced terrestrial reserve designs most when terrestrial habitat targets were low and little or none of the target was represented in pre-existing protected areas. Our results suggest that including marine values in the planning process will influence marbled murrelet terrestrial reserve designs most where substantial terrestrial nesting habitat still exists, where new reserves are relatively unconstrained by pre-existing reserves, or when conservation resources only allow the protection of a small fraction of available habitat. This paper presents a novel framework for incorporating multiple measures of ecological value in the spatial reserve design process and should be particularly useful for species that rely on multiple habitats during their life cycle.  相似文献   

8.
Catostomid fishes are a diverse family of 76+ freshwater species that are distributed across North America in many different habitats. This group of fish is facing a variety of impacts and conservation issues that are somewhat unique relative to more economically valuable and heavily managed fish species. Here, we present a brief series of case studies to highlight the threats such as migration barriers, flow regulation, environmental contamination, habitat degradation, exploitation and impacts from introduced (non-native) species that are facing catostomids in different regions. Collectively, the case studies reveal that individual species usually are not threatened by a single, isolated factor. Instead, species in general face numerous stressors that threaten multiple stages of their life history. Several factors have retarded sucker conservation including widespread inabilities of field workers to distinguish some species, lack of basic natural history and ecological knowledge of life history, and the misconception that suckers are tolerant of degraded conditions and are of little social or ecological value. Without a specific constituent group lobbying for conservation of non-game fishes, all such species, including members of the catostomid family, will continue to face serious risks because of neglect, ignorance, and misunderstanding. We suggest that conservation strategies should incorporate research and education/outreach components. Other conservation strategies that would be effective for protecting suckers include freshwater protected areas for critical habitat, restoration of degraded habitat, and design of catostomid-friendly fish bypass facilities. We believe that the plight of the catostomids is representative of the threats facing many other non-game freshwater fishes with diverse life-history strategies globally.  相似文献   

9.
暗管改碱技术试验区不同生境盐生植物资源及其群落特征   总被引:1,自引:0,他引:1  
盐生植物群落的空间格局因受土壤盐碱化的影响而呈现一定的地域性差异,其群落特征及分布对土壤盐碱化程度具有良好的指示作用。研究盐碱地区盐生植物群落特征及其分布规律,对补充和完善土壤盐碱化程度的检测和评估方法及当地盐碱地的改良和生态环境治理均具有一定的指导意义。本文以河北沧州黄骅市暗管改碱技术试验区为例,采用五点取样法分别对地下埋设暗管的荒地、夏季休耕地和未埋设暗管的荒地、夏季休耕地4种生境的植被进行调查,并采用聚类分析方法和Shannon-Wiener指数、Pielou均匀度指数、Simpson指数等分析4种生境下盐生植物资源及其群落特征。结果表明,被调查的20个样方内共有植物8科17属19种,均为草本植物,划分为5种植物群落类型。地下埋设暗管后,抗盐能力相对较低的假盐生植物和非盐生植物逐渐替代真盐生植物,成为荒地和夏季休耕地植物群落的优势种。并且地下埋设暗管的荒地和夏季休耕地物种多样性指数和均匀度指数均高于未埋设暗管的荒地和夏季休耕地。由此可见,暗管改碱技术的实施能在一定程度上降低土壤盐渍化程度,有利于保护和提高植物物种多样性,对盐碱地生态环境质量的改善具有重要意义,建议对其进行进一步研究及推广应用。  相似文献   

10.
Within species habitat use may depend on age, season or sex of an individual. The distribution of males and females may vary both temporally and spatially due to differences in the costs of reproduction and the distribution of critical resources. Conservation of a species requires knowledge of the habitat use of both sexes in order to predict the population size and protect all habitats that a species requires. Adult dragonfly populations often have highly male-biased sex ratios at the breeding habitat. This bias has been attributed to females using alternative habitats to avoid male harassment, or to high female mortality. We monitored adult Hine’s emerald dragonfly (Somatochlora hineana Williamson) populations, in breeding and non-breeding habitats in Door County, Wisconsin and found significant differences in habitat use between males and females. Males primarily used wetland habitats, while females primarily used dry meadows and marginal breeding habitats, only coming into wetlands to lay-eggs or find mates. We assessed food resources in the different habitats and found that high quality insect prey (primarily adult Diptera) were more available in the wetland habitat, indicating that these areas were likely a more productive foraging area for adult dragonflies. The fact that females appear to avoid the wetland habitat is consistent with the hypothesis that male harassment alters female distribution patterns. Consideration of the patterns of habitat use by S. hineana indicates the need to develop a broader understanding of the importance of non-wetland areas in the conservation of wetland species.  相似文献   

11.
Over the last three decades, the presence and functional roles of arbuscular mycorrhizal (AM) fungi in wetland habitats have received increasing attention. This review summarized the mycorrhizal status in wetlands and the effect of flooding on AM fungal colonization. Plants of 99 families living in 31 different habitats have been found to be associated with AM fungi, even including submerged aquatic plants and several plant species that were thought to be nonmycorrhizal (Cyperaceae, Chenopodiaceae, and Plumbaginaceae). The functions of AM fungi in wetland ecological systems could be concluded as their influences on the composition, succession, and diversity of the wetland plant community, and the growth and nutrition of wetland plants. Affecting the composition, succession, and diversity of the wetland plant community, AM fungi have positive, negative, or neutral effects on the performance of different wetland species under different conditions. The factors that affect the application effect of AM fungi in constructed wetland (CW) include flooding, phosphorus, plant species, aerenchyma, salinity, CW types, operation modes of CW, and wastewater quality. The generalist AM fungi strains can be established spontaneously, rapidly, and extensively in wastewater bioremediation technical installations; therefore, AM fungi can be considered ideal inhabitants of technical installations for the plant-based bioremediation of groundwater contaminated by organic pollutants or other contaminants. In the future, roles of AM fungi and factors that affect the purifying capacity of AM-CW system must be understood to optimize CW ecosystem.  相似文献   

12.
[目的]分析巴丹吉林沙漠边缘地区植物区系及植被资源利用,为日后巴丹吉林沙漠区域的植被恢复、保护和利用提供理论依据和参考。[方法]以植物地理学的原理和方法,结合实地调查情况,对巴丹吉林沙漠边缘特殊生境的植物区系组成、区系分布进行系统的讨论,划分该区植被资源类型并且提出保护措施和利用方法。[结果]巴丹吉林沙漠边缘地区植被为典型的荒漠植被,共记录植物13科30属32种,其中裸子植物1科1属1种,被子植物12科29属31种。同时受地形、地貌、气候等生境影响,该地植物区系分布有明显差异性。植被资源具体可分为食(饲)用植物(22种)、药用植物(12种)、生态植物(17种)和其他资源4大类。提出了迁移物种、丰富度和多样性等保护方法;归纳了对水资源的控制,合理放牧、适当封育、药用资源合理采挖和多种资源综合利用的方式。[结论]巴丹吉林沙漠边远地区植被调查分析对沙漠化的防治和沙漠资源的利用有重大作用。  相似文献   

13.
Many studies have reported increased numbers of certain synanthropic species in urbanizing landscapes, but few have evaluated if urban habitats constitute ecological traps for these species. The Northern cardinal (Cardinalis cardinalis) was used as a model species to evaluate if urban riparian forests might act as ecological traps for understory-nesting birds. Cardinals were surveyed within 2-ha riparian forest plots within rural (n = 6) and urban (n = 6) landscapes in Ohio USA during breeding and non-breeding seasons 2003-2005. Cues used by cardinals to select habitats were identified based on measurements surrounding 219 nests and in 106 randomly-located plots and 96 systematically-located plots. Productivity of 161 cardinal pairs and survival of 180 adults were monitored from late March-September, 2003-2005. Cardinals were 1.7× (in the breeding season) to nearly 4× (in non-breeding season) more abundant in urban than rural forests, and the results suggest that these differences in abundance stemmed from urban-associated changes in habitat and microclimate features used by cardinals to select habitats. Most notably, cardinals were strongly associated with dense understory vegetation and warmer minimum January temperatures, both of which were promoted as urban development increased within the landscapes surrounding riparian forests. Although other studies suggest mismatches between the habitat cues used by cardinals and how those features affect nesting success (e.g., higher nest predation in exotic shrubs), these results provide no evidence that urban forests were acting as ecological traps for cardinals. Instead, cardinals in urban and rural forests had similar numbers of nesting attempts, young fledged over the breeding season, and apparent annual survival rates. Thus, these findings do not support for the idea that urban forests in central Ohio represent ecological traps for synanthropic understory birds.  相似文献   

14.
The causes of moss rarity were analysed in three neighbouring countries. Estonia, Latvia and Lithuania, situated along the coast of the Baltic Sea, cover together 175,000 km2. They belong to the same vegetation zone, and have similar economic and natural history, but there are still certain differences in climate, bedrock, soil and land use.Three frequency groups of mosses, altogether 184 species, were compared in this study: (1) mosses present in all three countries and frequent in every country, (2) mosses present in all three countries, but rare in every country and (3) mosses present in only one country and rare in this country, i.e. very rare mosses. The distribution of moss species according to families, life history characters (sexuality, spore size and life span) and ecological characters (substrate and community type preferences) were compared among these three groups.There were differences in the distribution of species according to families between the three frequency groups. Frequent and rare moss species groups were also characterised by different life historical (life span) and ecological characteristics (substrate pH and community type). Comparison of ecological indexes in the group of country specific mosses revealed that species preferences regarding soil alkalinity follow the pattern of the distribution of alkaline soils in the three countries. Species occurring in the most southern country - Lithuania - are characterised by highest temperature indexes.On the basis of the studied species we can conclude that taxonomical and life historical trends explain one part of rarity in the studied region, while local ecological conditions in connection with land use are responsible for the other part.  相似文献   

15.
The Chinese or Swinhoe's Egret (Egretta eulophotes) is a species that is threatened with extinction. Very little is known of its habits, and so observations made in Hong Kong, where two or three pairs nested in 1969, are detailed. The species feeds primarily in shallow estuarine water, adopting the parasolling method of active pursuit that is characteristic of the American Snowy Egret. Swinhoe's Egret (and not the Little Egret as many authors have suggested) seems, therefore, to be the ecological equivalent of the New World Snowy Egret. Affinities are discussed, and it is suggested that Swinhoe's Egret has been replaced by the better-adapted Little Egret in inland freshwater areas and by the Reef Egret in marine habitats. In consequence, it now survives only as a relict population inhabiting a specialized niche in localized estuarine and delta areas of the Orient. Swinhoe's Egret appears to be in danger of extinction for biological reasons but Man may have increased the danger. Following the ravages of the plume trade, the Little Egret—by virtue of initially having a larger and more widely dispersed population and therefore a greater potential for population increase —seems to have expanded within the ecological niche that it previously shared with Swinhoe's Egret. Swinhoe's Egret now poses a difficult problem in conservation that is made the more intractable by its virtual restriction to mainland China. There is a need to ensure as much scientific documentation as possible during the next decade, in view of the bird's biological significance in relation to other members of the genus.  相似文献   

16.
Remaining patches of semi-natural grasslands are hot spots for biodiversity in modern agricultural landscapes. In Sweden semi-natural pastures cover approximately 500,000 ha. However, power-line corridors, road verges and clear-cuts cover larger areas (in total about 2,000,000 ha), and these open, less intensively managed habitats are potentially important for species associated with taller vegetation and flower resources (e.g. pollinating insects). The aim of the present study was to evaluate the relative importance of semi-natural pastures and the other three open habitats for butterflies in 12 forest-farmland mosaic landscapes in south central Sweden. Species composition differed significantly between habitats in multivariate analyses. Power-line corridors and semi-natural pastures harbored several species that were disproportionally abundant in these habitats (13 and 8 species, respectively), and power-line corridors also harbored several species that were classified as typical in indicator species analyses. There were more butterfly species, higher abundances and a tendency for more individuals of red-listed species in power-line corridors than in the other three habitats. Effects of the surrounding landscape composition seemed to be weaker than that of the local habitat. However, species composition was significantly associated with landscape composition and species with intermediate and low mobility were more abundant in forested landscapes than in landscapes dominated by arable fields. Analyses of flying time and host plants for larvae suggest that early flying species and species associated with dwarf shrubs were more common in power-line corridors than in the other habitats. A landscape perspective, which takes several habitats into account, is needed for conservation of butterfly communities in forest-farmland landscapes. Power-line corridors and road verges offer possibilities for creating habitats that are suitable for pollinating insects through conservation-oriented management.  相似文献   

17.
河道生态系统中的河岸侵蚀和滨水缓冲带建设倍受关注。以上海市浦东新区机场镇的生态河道示范工程为例,探讨了以生态修复和稳定坡岸为目标的植物护坡技术在生态河道坡岸修复中的应用及其生态效应。在不同河段分别采用了全系列生态护坡、土壤生物工程护坡和复合式生物稳定等3类植物护坡技术。通过对工程实施后3a(2004年~2006年)来的生态监测发现,护坡植物生长良好,新生枝叶和根系的护坡作用明显,土壤抗剪强度明显增加,河岸土壤侵蚀得到有效控制,坡岸的结构稳定性增强;同时河岸生境得到改善,本地植物快速恢复,生物多样性增加,河岸植物群落结构由单一结构向复杂结构转变,生态稳定性逐渐增强。生态河道的植物坡岸修复技术可以在我国各类岸坡的生态修复和边坡稳定中广泛运用。  相似文献   

18.
植物护坡及其生态效应研究   总被引:8,自引:0,他引:8  
河道生态系统中的河岸侵蚀和滨水缓冲带建设倍受关注。以上海市浦东新区机场镇的生态河道示范工程为例,探讨了以生态修复和稳定坡岸为目标的植物护坡技术在生态河道坡岸修复中的应用及其生态效应。在不同河段分别采用了全系列生态护坡、土壤生物工程护坡和复合式生物稳定等3类植物护坡技术。通过对工程实施后3a(2004年~2006年)来的生态监测发现,护坡植物生长良好,新生枝叶和根系的护坡作用明显,土壤抗剪强度明显增加,河岸土壤侵蚀得到有效控制,坡岸的结构稳定性增强;同时河岸生境得到改善,本地植物快速恢复,生物多样性增加,河岸植物群落结构由单一结构向复杂结构转变,生态稳定性逐渐增强。生态河道的植物坡岸修复技术可以在我国各类岸坡的生态修复和边坡稳定中广泛运用。  相似文献   

19.
The conservation of rare species on islands is a special challenge, especially when the islands are faced with increasing human impact. Two endangered wild felids in Japan provide a contrast that is useful for examining conservation strategies. The Iriomote cat (Prionailurus bengalensis iriomotensis) is endemic to Iriomotejima Island in Okinawa, and the Tsushima leopard cat (Prionailurus bengalensis euptilurus) occurs in the Tsushima islands in Japan, although a related subspecies found in the Korean Peninsula. Population size was approximately 100 individuals for each subspecies. While the population of Iriomote cat appears relatively stable, the population and abundance of the Tsushima leopard cat has decreased in recent decades. Because of their small population sizes and restricted habitats both are listed as endangered species/subspecies in Japan’s Red List, and the Iriomote cat is listed as an endangered subspecies in the IUCN Red List. Although both are similar-sized felids living on small islands, their ecological characteristics such as food habit, habitat selection, and density differ. These differences seem to be caused by the climate, the biological environment (the species composition of fauna in each island, and the presence of competitors), and the artificial background. The threats facing these two felids are also similar. Habitat destruction, traffic accidents, and negative influences by introduced species are the principal threats to be addressed for their conservation. At the same time, there are differences in the degree of impact by each threat, in each species’ conservation programs in practice, and in the stages of progress and operation of programs. These differences are partly because they have different ecological features and partly because the social background of each island, such as human population, main industry, and historical relationship between human and wildlife, are quite different. We will compare the ecology and state of these two wild felids and discuss the different conservational situations in relation to felid ecology and human society.  相似文献   

20.
《Biological conservation》1986,35(3):215-258
This paper analyses the ecological status of the Barbary macaque in the Djebala region of North Morocco. Results are presented of vegetation surveys and of preliminary studies on resource availability, diet and habitat use of the Barbary macaque in the four main habitat types where the species occurs.Factors affecting the distribution and abundance of the monkeys are considered and data on the past and present distribution in the Djebala habitats are discussed in relation to the influence of man. An assessment is made of whether current monkey populations reflect real differences in the suitability of habitats (i.e. habitat quality and productivity) or whether they are restricted purely by human interference. The latter term is defined both as direct predation and indirect action through modification of habitats via grazing of domestic stock, burning and tree-felling.  相似文献   

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