共查询到20条相似文献，搜索用时 0 毫秒
1.
NATHAN A. KLAUS DAVID A. BUEHLER ARNOLD M. SAXTON 《The Journal of wildlife management》2005,69(1):222-234
Abstract: We used a 60-yr forest simulation of the Cherokee National Forest, Tennessee, USA, to model the effects of timber harvest and natural disturbance upon habitat availability for 6 songbird species: Acadian flycatcher (Epidonax virescens), blue-headed vireo (Vireo solitarius), chestnut-sided warbler (Dendroica pensylvanica), tufted titmouse (Parus bicolor), yellow-billed cuckoo (Coccyzus americanus), and yellow-throated warbler (Dendroica dominica). Forest simulations, based on expected harvest intensities and historic levels of natural disturbance, were used to update a stand inventory database at 10-yr intervals between 1993 and 2053. Habitat models for the 6 bird species were applied to the updated stand inventory and available habitat quantified for each decade. Late-successional species showed substantial increases in habitat availability over the 60-yr period at most harvest intensities, whereas habitat for early-successional species was stable or declined at most harvest intensities. Acadian flycatcher, yellow-throated warbler, and blue-headed vireo habitat increased by 200%, 213%, and 40%, respectively, whereas tufted titmouse habitat remained relatively constant at expected harvest levels. Chestnut-sided warbler habitat was stable at expected harvest levels but declined at lower harvest intensities, and yellow-billed cuckoo habitat declined by 37% at expected harvest levels. Natural disturbance had little effect on habitat availability for any bird species compared to the effects of timber harvests and increasing forest age. Our models suggest that anthropogenic disturbance, and lack thereof, can play a definitive role determining habitat availability and population viability for forest songbirds. 相似文献
2.
应用“相邻格子法”对浙江古田山国家自然保护区的甜槠种群进行调查 ,将 2 5个样地分为不同演替阶段和不同生境的森林群落两大类型。对甜槠种群结构和动态进行分析 ,绘制甜槠种群大小结构图和存活曲线 ;并用泊松方差 /均值比率等 5个聚集度指标测定其种群分布格局。结果显示 :马尾松林→马尾松针阔叶混交林→次生常绿阔叶林→成熟山坡常绿阔叶林的演替过程中 ,马尾松林中甜槠个体极少 ,针阔叶混交林中种群结构为增长型 ;次生和成熟常绿阔叶林中其种群结构都比较稳定 ,但从群落外貌和结构仍可看出前者的次生性。不同生境的群落包括成熟沟谷常绿阔叶林、成熟山坡常绿阔叶林、黄山松林和黄山松针阔叶混交林 ,甜槠由沟谷地带的零星个体变为山坡上的稳定型种群 ,中山地带的黄山松林和黄山松针阔叶混交林中甜槠种群呈增长型 ,但不会取代黄山松的优势地位。种群空间格局大都为集群分布 ,并符合负二项式分布 ,仅两个次生群落的甜槠种群因缺 、 、 级幼苗而呈随机分布。此外 ,对成熟常绿阔叶林中不同大小级个体分布格局动态的研究表明 :甜槠在幼苗、幼树时为集群分布 ,随着甜槠个体进一步增大 ,其分布格局由集群分布变为随机分布。甜槠以其较强的更新能力 ,成为本区低海拔成熟常绿阔叶林中十分稳定的优势种 相似文献
3.
4.
Attempts to explain the orders-of-magnitude variation observed in animal population sizes have principally focused on intrinsic differences between the taxa compared, but with limited success: most variation remains unexplained by such studies. However, animal population sizes may also vary in response to extrinsic factors, such as the environment occupied or the influence of human activities. Here, we use new estimates of the global population sizes of threatened bird species to examine extrinsic correlates of variation in their numbers, using general linear modelling and methods to control for phylogenetic relatedness. Threatened bird population sizes varied significantly with several extrinsic factors, including altitude, biogeographical region inhabited, type of extinction threat faced, and habitat used. They also vary with geographical range size, which was included in the analysis to control for its potentially confounding effects on the results. Details of the observed relationships, which vary with analytical method, are discussed. However, apart from geographical range size, none of the extrinsic variables analysed here explain more than a small percentage of the variation in threatened bird population sizes. Thus, it seems likely that a comprehensive explanation for why some species are common while others are rare will not be dominated by a single factor. 相似文献
5.
Corey S. Shake Christopher E. Moorman Michael R. Burchell II 《The Journal of wildlife management》2011,75(4):825-835
The effects of habitat edges on nest survival of shrubland birds, many of which have experienced significant declines in the eastern United States, have not been thoroughly studied. In 2007 and 2008, we collected data on nests of 5 shrubland passerine species in 12 early successional forest patches in North Carolina, USA. We used model selection methods to assess the effect of distance to cropland and mature forest edge on nest predation rates and additionally accounted for temporal trends, nest stage, vegetation structure, and landscape context. For nests of all species combined, nest predation decreased with increasing distance to cropland edge, by nearly 50% at 250 m from the cropland edge. Nest predation of all species combined also was higher in patches with taller saplings and less understory vegetation, especially in the second year of our study when trees were 4–6 m tall. Predation of field sparrow (Spizella pusilla) nests was lower in landscapes with higher agricultural landcover. Nest predation risk for shrubland birds appears to be greater near agricultural edges than mature forest edges, and natural forest succession may drive patterns of local extirpation of shrubland birds in early successional forest patches. Thus, we suggest that habitat patches managed for shrubland bird populations should be considerably large or wide (>250 m) when adjacent to crop fields and maintained in structurally diverse early seral stages. © 2011 The Wildlife Society. 相似文献
6.
7.
8.
Hemanta Dhakal Hari Prasad Sharma Christopher J. W. McClure Munir Virani Brian W. Rolek Narendra Man Babu Pradhan Krishna Prasad Bhusal 《Ecology and evolution》2022,12(1)
Due to an abundance and diversity of vultures, Nepal is one of the most important countries for vulture conservation. Within Nepal, the Pokhara Valley is especially significant. We examine the distribution of vultures within the Pokhara Valley by conducting counts at 11 potential feeding or roosting sites using point count method. We further surveyed people of the valley regarding their perception of vulture ecology and conservation, knowledge of diclofenac use within the valley, and burial of livestock carcasses. We detected eight species of vultures, four of which are currently threatened with extinction. White‐rumped vulture Gyps bengalensis, Egyptian vulture Nephron percnopterus, and Himalayan vulture G. himalayensis were the most abundant. Almost all respondents (98%) had sighted the vultures in the wild. Formally educated respondents reported seeing vultures’ slightly more than nonformally educated respondents. Fifty‐eight percent respondents suspected habitat loss was the major threat for the vulture population decline in Pokhara Valley, and 97% respondents were not aware of any diclofenac use. The knowledge of vultures in people with different age groups suggests a more awareness programs are needed for local people, especially those who carry out animal husbandry and provide livestock to the vulture restaurant. 相似文献
9.
Evolutionary age and risk of extinction in the global avifauna 总被引：1，自引：0，他引：1
Species at high risk of extinction are not distributed at random among higher taxa. Here we demonstrate that there is a positive relationship between the proportion of species in a taxon which are considered to be threatened and the evolutionary age of that taxon, both for the global avifauna and the avifauna of the New World. The potential mechanisms and consequences of the relationship are examined. 相似文献
10.
Jamie Newman Darren Scott Corey Bragg Sam McKechnie Henrik Moller David Fletcher 《New Zealand journal of zoology.》2013,40(3):307-323
Abstract Recent comprehensive survey data from multiple New Zealand offshore islands were combined with demographic population models to produce the first formal estimate of the total population of sooty shearwaters within New Zealand territory. We estimated the total population over 1994–2005 to be 21.3 (19.0–23.6) million individual birds in the New Zealand region. This population consisted of 12.8 (12.0–13.6) million adults, 2.8 (2.5–3.1) million chicks, and 4.4 (4.2–4.7) million breeding pairs. Breeding sooty shearwaters were concentrated primarily around the southern islands of New Zealand, with 53% breeding in the Titi Islands surrounding Rakiura (Stewart Island). Rakiura Maori muttonbirders were estimated to harvest 360 000 (320 000–400 000) sooty shearwaters per year, equivalent to 18% of the chicks produced in the harvested areas and 13% of chicks in the New Zealand region. Overall, 11% of the chicks within the Titi Islands live on unharvested ground. Systematic and widespread surveys of breeding colonies in South America are needed before a reliable global sooty shearwater population estimate can be calculated. 相似文献
11.
Tainá Figueras Dorado‐Rodrigues Viviane Maria Guedes Layme Fernando Henrique Barbosa Silva Cátia Nunes da Cunha Christine Strüssmann 《Austral ecology》2015,40(5):547-557
In many parts of the world, replacement of natural grasslands by woody plants has resulted in a decrease of pasture areas and in habitat loss for a variety of animal species, including amphibians. Wetlands are especially susceptible to invasive plants, both native and exotic, but the effects of such invasions on animal assemblages remain poorly understood. Here, we present information on the impact of selected environmental variables, especially coverage by the native shrub Combretum laxum Jacq., on the structure of an anuran assemblage in the Pantanal, a huge flood‐pulsed South American wetland. Anurans were surveyed during the rainy season in 17 plots, which differed in extent of C. laxum coverage, leaf litter volume, soil moisture and distance to permanently wet areas. Effects of these environmental variables on the species number, relative abundance and composition of the anuran assemblage were evaluated using multivariate statistical analyses. We captured 1203 anurans, of 21 species from four families. Both the number of species and the relative abundance of anurans were lower in plots with greater C. laxum coverage, which also influenced anuran species composition. Number of species was highest in plots located closest to permanently wet areas, which provide protection from desiccation and other resources during the Pantanal dry season, and so could be considered source areas of anurans. While many anuran species were negatively affected by the homogenization of the landscape caused by shrub encroachment, some seemed to be favoured in such circumstances. For these, dense shrub encroachment into natural grasslands may provide safer migratory routes to permanently wet habitats. Thus, at the mesoscale, a mosaic of areas with different levels of coverage by C. laxum (shrub islands) may aid anuran assemblages in the Pantanal wetlands, facilitating the maintenance of higher beta and gamma diversity. 相似文献
12.
To assess the effects of timber harvesting on headwater streams in upland forests, benthic community structure was contrasted among four dominant forest management types (old growth, red alder-dominated young growth, conifer-dominated young growth, clearcut) and instream habitats (woody debris, cobble, gravel) in southeastern Alaska. Benthos in streams of previously harvested areas resulted in increased richness, densities and biomass relative to old growth types, particularly in young growth stands with a red alder-dominated riparian canopy. Woody debris and gravel habitats supported a combination of higher densities and biomass of invertebrates than cobble habitats. In addition, woody debris also supported a richer and more diverse invertebrate fauna than either cobble or gravel substrates. Maintaining both a woody debris source and a red alder component in regenerating riparian forests following timber harvesting should support greater invertebrate densities and diversity following clearcutting. 相似文献
13.
Emma A. Higgins Doreen S. Boyd Tom W. Brown Sarah C. Owen Adam C. Algar 《Ecology and evolution》2021,11(16):11414
The question of what controls animal abundance has always been fundamental to ecology, but given rapid environmental change, understanding the drivers and mechanisms governing abundance is more important than ever. Here, we determine how multidimensional environments and niches interact to determine population abundance along a tropical habitat gradient. Focusing on the endemic lizard Anolis bicaorum on the island of Utila (Honduras), we evaluate direct and indirect effects of three interacting niche axes on abundance: thermal habitat quality, structural habitat quality, and prey availability. We measured A. bicaorum abundance across a series of thirteen plots and used N‐mixture models and path analysis to disentangle direct and indirect effects of these factors. Results showed that thermal habitat quality and prey biomass both had positive direct effects on anole abundance. However, thermal habitat quality also influenced prey biomass, leading to a strong indirect effect on abundance. Thermal habitat quality was primarily a function of canopy density, measured as leaf area index (LAI). Despite having little direct effect on abundance, LAI had a strong overall effect mediated by thermal quality and prey biomass. Our results demonstrate the role of multidimensional environments and niche interactions in determining animal abundance and highlight the need to consider interactions between thermal niches and trophic interactions to understand variation in abundance, rather than focusing solely on changes in the physical environment. 相似文献
14.
Aurélie Khimoun Cyril Eraud Anthony Ollivier Emilie Arnoux Vincent Rocheteau Marine Bely Emilie Lefol Martin Delpuech Marie‐Laure Carpentier Gilles Leblond Anthony Levesque Anaïs Charbonnel Bruno Faivre Stéphane Garnier 《Molecular ecology》2016,25(16):3831-3844
Habitat fragmentation is one of the most severe threats to biodiversity as it may lead to changes in population genetic structure, with ultimate modifications of species evolutionary potential and local extinctions. Nonetheless, fragmentation does not equally affect all species and identifying which ecological traits are related to species sensitivity to habitat fragmentation could help prioritization of conservation efforts. Despite the theoretical link between species ecology and extinction proneness, comparative studies explicitly testing the hypothesis that particular ecological traits underlies species‐specific population structure are rare. Here, we used a comparative approach on eight bird species, co‐occurring across the same fragmented landscape. For each species, we quantified relative levels of forest specialization and genetic differentiation among populations. To test the link between forest specialization and susceptibility to forest fragmentation, we assessed species responses to fragmentation by comparing levels of genetic differentiation between continuous and fragmented forest landscapes. Our results revealed a significant and substantial population structure at a very small spatial scale for mobile organisms such as birds. More importantly, we found that specialist species are more affected by forest fragmentation than generalist ones. Finally, our results suggest that even a simple habitat specialization index can be a satisfying predictor of genetic and demographic consequences of habitat fragmentation, providing a reliable practical and quantitative tool for conservation biology. 相似文献
15.
Guilherme H. S. Freitas Lílian M. Costa Pedro H. V. B. P. Silva Anderson V. Chaves Leonardo C. Ribeiro Marcos Rodrigues 《Journal of Field Ornithology》2019,90(2):128-142
Birds in the genus Cinclodes are habitat specialists, with most restricted to the highlands of South America. The recently described Cipo Cinclodes (C. espinhacensis) is isolated in the southern Espinhaço Range of Brazil and is considered Endangered in Brazil and Near Threatened by the IUCN, but as a subspecies of Long‐tailed Cinclodes (C. pabsti). We examined the population and spatial ecology of Cipo Cinclodes at two geographic scales to improve our understanding of their basic biology and conservation status. We monitored 30 birds at Serra do Breu and found relatively large home ranges (mean = 9.3 ha), a density of paired adults of 0.09/ha, a male‐skewed adult sex ratio (males/total adults = 0.57) due to territories occupied by unpaired males, and long‐term site fidelity. Cipo Cinclodes used all habitat types available in our study area, including rocky outcrops, grasslands, and riparian areas, but habitat selection analyses revealed the importance of riparian areas for foraging and rocky outcrops for nesting. At the species distribution scale, we compiled known and novel recorded occurrence points and used them to calculate the extent of occurrence (EOO) and the area of occupancy (AOO). We used a Maxent species distribution model to generate a binary map to estimate upper limits for EOO (EOO around the model predicted area) and AOO (comprised by the model predicted area within the EOO). We obtained 41 locations, resulting in an EOO of 890.7 km2 (up to 1748.7 km2) and an AOO of 100 km2 (up to 327.5 km2). The global population is estimated to be between 880 and 2882 birds, which is concerning because small populations are at risk of extinction due to demographic stochasticity, genetic drift, and the interaction of these factors. As such, our results support the designation of Cipo Cinclodes as Endangered on the Brazilian red list. 相似文献
16.
Griffiths D 《The Journal of animal ecology》2006,75(3):734-751
1. Species lists for regions of Europe defined by Illies (1978, Limnofauna Europaea, 2nd edn. Gustav Fischer Verlag, Stuttgart), and augmented by information from Maitland (2000, Guide to Freshwater Fish of Britain and Europe. Hamlyn, London), are used to describe patterns in freshwater fish species richness and to examine the contribution of habitat preference, migration, body size and glacial history to these patterns. 2. The number of non-endemic species declines to the north and west, with increasing distance from the Ponto-Caspian region, the main source area, whereas endemic species richness declines only with latitude. 3. Habitat generalists tend to be migratory while riverine specialists are usually resident. Similar numbers of riverine species and generalists occur in Europe as a whole but generalists dominate in regional faunas and, to an increasing extent, in more isolated, formerly glaciated areas. Very few lacustrine specialists were found, reflecting the geologically ephemeral nature of lakes. Only 8% of riverine species have colonized glaciated areas, compared with more than half the generalist species, and the number declines rapidly with increasing distance from the source area. 4. Diadromous species show no geographical variation in species richness but potamodromous and resident species are affected by glaciation and by mountain and marine barriers. 5. The mean body size of regional faunas increases with latitude because there are relatively fewer small species in more distant, glaciated areas. 6. About half the species occurring in Europe are restricted to one region and the majority of these endemics occur in barrier regions with Mediterranean climates. Species in glaciated regions have much larger range sizes. Habitat preference and migration type, not body size, are the main determinants of range size. 7. Freshwater habitat availability varies across Europe with glaciated areas having more lakes of a given size than unglaciated areas. Catchment size is greatest at mid-latitudes. For a given catchment size rivers in glaciated areas are shorter. 8. The results support the notion that habitat variability, on both short and long time scales, favours colonization ability, which requires large body size. 9. As a result of their limited vagility northern fish faunas are depauperate, show high levels of plasticity and polymorphism and may show elevated speciation rates. The isolated southern faunas of the Iberian and Italian peninsulas and the Balkans are rich in endemic species but may be subject to extinctions because of the spread of the highly seasonal Mediterranean climate. 相似文献
17.
大兴安岭呼中区紫貂生境格局变化及采伐的影响 总被引：1，自引：0，他引：1
本文根据紫貂（Martes zibellina）行为生态学特征,利用景观生态学的原理和技术,将大兴安岭呼中区紫貂生境划分成最适、一般适宜和非适宜三种类型。以其紧邻的呼中自然保护区核心区1989年的生境格局代表呼中区1970年开发前的原始生境,揭示原始生境、1989年、2000年3个时期紫貂生境格局及变化。结果表明,1970-2000年紫貂生境格局持续恶化,已极不利于紫貂的生存。适宜生境向非适宜生境呈单一方向转变,且适宜生境由沟谷两侧向远离河谷的森林腹地大幅度萎缩。生境格局变化与经营时问长短关系密切,原始状态是以适宜生境为基质的均质状态,开发至一定时期,生境格局的异质化程度增大,继续开发则异质化程度又减小,形成以非适宜生境为基质的相对均质状态。大于巢区最小面积f4km0）的生境斑块的面积百分比、斑块密度明显下降,斑块间距离显著增大。进而对导致生境格局变化的要素进行分析后发现,持续采伐是紫貂生境格局变化的主要驱动因子,采伐改变了植被条件,而植被条件的非适宜性造成了紫貂非适宜生境。1989-2000年的采伐格局也并不合理,各年伐区在研究区内均匀分布,采伐设计时没有考虑动物生境保护。但可以推断,1999年后开始逐步实施的“天然林保护工程”有利于紫貂生境的恢复,本研究强调森林采伐经营的空间格局与动物生境保护之间的关系,旨在促进决策部门将生物保护作为采伐经营政策制定的重要决策因子。 相似文献
18.
Andrew D. George Paul A. Porneluzi Janet M. Haslerig John Faaborg 《The Journal of wildlife management》2019,83(7):1508-1514
Conservation of birds that breed in early-successional forests will require an understanding of their response to patch size and shape during the early seral stages following disturbance. We modeled the effects of patch area, patch shape, and time period following harvest on territory densities of 5 shrubland bird species and bird community composition in 36 clearcuts from 1997 to 2014 in the Missouri Ozarks, USA. Our best-supported models indicated that densities of indigo bunting (Passerina cyanea), yellow-breasted chat (Icteria virens), and prairie warbler (Setophaga discolor) declined from the early time period (1–7 years post-harvest) to the late time period (12–18 years post-harvest), regardless of clearcut area or shape. Yellow-breasted chat density and bird species richness were positively related to clearcut shape complexity. Bird species richness increased, and bird species density decreased with clearcut area during both time periods. Non-metric multidimensional scaling indicated that bird community composition was strongly related to time since harvest. Within the spatial scale of our study, successional stage is more influential than clearcut size and shape, and some bird species may benefit from relatively small or irregularly shaped clearcuts. © 2019 The Wildlife Society. 相似文献
19.
20.
CHRISTOPHER INGLESFIELD MICHAEL BEGON † 《Biological journal of the Linnean Society. Linnean Society of London》1981,15(3):259-278
The distribution of Drosophila subobscura adults within, and their movement through, open ground habitats has been investigated, along with the status of such individuals within populations as a whole. Movement occurs between open ground and woodland, to some extent as a result of passive transport by air currents, but flies can remain in open ground for at least several days at a time. There are no detectable differences in either the reproductive age-structure or the body-size distributions of flies collected from woodland and open ground habitats, although a significantly higher proportion of females are found in open ground than in woodland. The large number of gravid females in open ground provide the potential for breeding there, but circumstantial evidence suggests that this is unlikely to occur. Rather, their presence appears to reflect the foraging strategy adopted by females in response to their high nutritional requirements. The flux of flies through open ground between woodlands suggests that previous estimates of the genetically-important parameter, effective population size, have been seriously underestimated for natural D. subobscura populations. 相似文献