77 resultados para Mountain railroads


Relevância:

10.00% 10.00%

Publicador:

Resumo:

新疆中部地区位于西北内陆干旱一半干旱区,是欧亚大陆的地理中心,是中纬度内陆干旱区代表性区域,也是全球变化敏感区域之一,基本特点是气候干旱、水资源匮乏、植被稀少、荒漠广布,生态系统脆弱。在研究区域内,天山山脉海拔高度差异5 000 m左右,随海拔梯度下降依次出现高山冰雪带、高山亚高山草甸带、森林带、草原带、荒漠带、沙漠带等明显完整的植被垂直带,是开展现代孢粉学和植被变化研究的理想地点。本报告在立足于该区前人工作的基础上,从表土花粉、空气花粉和现代植被之间的关系入手开展现代孢粉学研究,探讨了花粉与植被的关系。 在研究区内,选择新疆阜康市和吉木萨尔县为研究地点,设计了一条从天山博格达峰附近雪线开始直至古尔班通古特沙漠长约100 km、宽约20 km的样带。沿样带,从高山座垫植被和草甸带开始,经过中海拔地带的云杉林,置到低海拔的荒漠,在山地海拔每下降20~100 m采集一个表土花粉样品,平原每间隔10~20 km采集一个表土花粉样品,同时做现代植被调查,共采集80个表土花粉样品和调查了86个现代植被样方;在天山乌鲁木齐河河源区的大西沟,从一号冰川前缘开始,沿山谷向下直到谷口,按海拔100 m间隔采集了14个表土样品,对表土花粉与植被之间的关系进行了探讨。为了弄清空气花粉传播、散布与气象因子和植被的关系,沿样带从高山到沙漠分别在天池气象站、中国科学院阜康荒漠生态系统定位研究站和北沙窝草炭试验地设置了三个风标式空气花粉收集器,从2001年7月至2002年7月连续收集空气花粉雨,收集了跨2个年度1周年的1 14个空气花粉样品,依据分析结果研究了空气花粉的传播和散布规律以及与表土花粉和植被之间的关系,这在新疆地区乃至全国尚属首次。 根据表土花粉分析结果和现代植被样方资料的分析以及天山中段主要植物种类沿海拔高度的分布特征,天山中段北坡垂直植被带谱为:高山座垫植被(>3 400 m)、高山亚高山草甸(3 400-2 700 m)、山地云杉林(2 700-1 720 m)、森林草原过渡带(1 720-1 300 m)、蒿类荒漠(1 300-700 m)和典型荒漠(<700 m)。表土花粉谱基本上反映了相同海拔高度的现代植被带,特别是在云杉林带,表土中雪岭云杉(Picea schrenkiana)花粉占优势;在蒿类荒漠植被带表土中蒿属(Artemisia)植物花粉非常丰富;在典型荒漠植被带的表土中藜科(Chenopodiaceae)植物花粉占绝对优势,因此可依据这些建群种植物花粉含量峰值的位置划分植物群落。 空气花粉样品分析结果表明:空气中花粉主要是现生植物当年生长产出的花粉,盛花期的花粉数量能较好地反映当地的植被状况。空气中的乔木植物花粉主要有云杉(Picea),其次是柳属(Salix);灌木草本植物花粉主要是藜科和蒿属,其次是菊科(Compositae)、禾本科(Gramineae)、柽柳科(Tamaricaceae)和麻黄属(Ephedra);空气中的花粉数量与植物的花期相对应,云杉等乔木植物盛花期在夏季5月末至7月初,灌木草本植物盛花期在夏秋季节。气温、降水、风速和风向等气象条件对空气中花粉数量有很大影响,其中风速和风向影响最大。从空气花粉和表土花粉的分析结果与现生植被对比,新疆中部地区的山谷上升气流是导致花粉“爬坡”现象的主要动力,在一定条件下,上升气流搬运花粉的数量和能力是十分可观的。 空气中的花粉是现生植物当年生长产出的花粉,表土中的花粉是多年花粉落地沉积的积累,植物盖度大,该植物的花粉在空气中和表土中数量相对就大。在新疆中部地区,空气花粉能反映当地和附近周边方圆约50 km的植被状况,其花粉组合特征与表土花粉和当地现生植被分布的对比研究,可以较好地寻找花粉与植被的关系。本研究报告的研究成果不仅为新疆地区的孢粉学研究增添新的内容,而且将有助于合理解释新疆地层中、尤其是第四纪以来的地层孢粉,较客观地恢复过去的植被景观,同时可为本地区的大气环境检测提供有重要价值的参考资料。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

森林作为陆地生态系统的主体,在全球陆地碳循环中起着决定性作用。实测和模型研究均表明北半球的森林是重要的大气CO2汇,在缓解全球碳收支失衡中发挥着关键作用。过去几十年北半球所经历的显著气候变化,已经很大地改变了陆地生态系统的碳平衡状况。随着未来100年气候变化继续增大,对未来气候变化下森林生态系统碳平衡的预测研究就尤为重要。 北京山区森林属于典型的暖温带森林生态系统,前人对本区森林的植被特征、生态系统结构和功能、养分循环以及长期动态变化等都进行了深入的研究。然而长期的人类活动已使本区原生的地带性植被破坏殆尽。因此,对该区域森林生态系统碳平衡的模拟研究可以帮助我们认识其生态系统碳平衡变化特点及未来气候变化对其潜在的影响。 本研究采用LPJ-GUESS植被动态机理模型,利用IPCC于2000年发布的《排放情景特别报告》(SRES)的A2和B2两种情景下不同气候模式对华北地区未来100年温度和降水预测的平均值以及相应大气CO2浓度变化情景进行驱动,模拟北京山区未来100年暖温带森林生态系统的净初级生产力和碳平衡,尽可能真实地反映未来百年的变化趋势。通过比较当前和未来气候情景下北京山区以辽东栎(Quercus liaotungensis)为优势种的落叶阔叶林、以白桦(Betula platyphylla)为主的落叶阔叶林和油松(Pinus tabulaeformis)为主的针阔混交林三种典型暖温带森林生态系统的碳平衡差异,了解未来北京山区这三种暖温带森林生态系统的碳源汇功能,认识气候变化和大气CO2浓度升高对净初级生产力(Net primary productivity, NPP)、净生态系统碳交换(Net ecosystem exchange, NEE)、土壤异养呼吸(Heterotrophic respiration, Rh)和碳储量(Carbon biomass, C biomass)的影响,以及不同生态系统碳平衡对气候变化响应的异质性。 结果表明,未来100年两种气候情景下三种森林生态系统的NPP和Rh均增加,并且A2情景下增加的程度更大。由于三种生态系统树种组成的不同,未来气候情景下各自NPP和Rh增加的比例不同,导致三者NEE的变化也相异:100年后辽东栎林由碳汇转变为弱碳源,白桦林仍保持为碳汇但功能减弱,油松林成为一个更大的碳汇。三种森林生态系统的碳生物量在未来气候情景下均增大,21世纪末与20世纪末相比:辽东栎林在A2情景下碳生物量增加的比例为27.6%,大于B2情景下的19.3%;白桦林和油松林在B2情景下碳生物量增加的比例分别为34.2%和52.2%,大于A2情景下的30.8%和28.4%。各森林类型碳平衡状况不同,原因除气候因素外,主要是由于树种组成的差异所导致。SRES A2和B2两种气候情景相比,相对较低的排放情景(B2)下,生态系统有更高的碳储量。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

We have made a set of chromosome-specific painting probes for the American mink by degenerate oligonucleotide primed-PCR (DOP-PCR) amplification of flow-sorted chromosomes. The painting probes were used to delimit homologous chromosomal segments among human, red fox, dog, cat and eight species of the family Mustelidae, including the European mink, steppe and forest polecats, least weasel, mountain weasel, Japanese sable, striped polecat, and badger. Based on the results of chromosome painting and G-banding, comparative maps between these species have been established. The integrated map demonstrates a high level of karyotype conservation among mustelid species. Comparative analysis of the conserved chromosomal segments among mustelids and outgroup species revealed 18 putative ancestral autosomal segments that probably represent the ancestral chromosomes, or chromosome arms, in the karyotype of the most recent ancestor of the family Mustelidae. The proposed 2n = 38 ancestral Mustelidae karyotype appears to have been retained in some modern mustelids, e.g., Martes, Lutra, ktonyx, and Vormela. The derivation of the mustelid karyotypes from the putative ancestral state resulted from centric fusions, fissions, the addition of heterochromatic arms, and occasional pericentric inversions. Our results confirm many of the evolutionary conclusions suggested by other data and strengthen the topology of the carnivore phylogenetic tree through the inclusion of genome-wide chromosome rearrangements. Copyright (C) 2002 S. KargerAG, Basel.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The phylogenetic relationships among worldwide species of genus Ochotona were investigated by sequencing mitochondrial cytochrome b and ND4 genes. Parsimony and neighbor-joining analyses of the sequence data yielded congruent results that strongly indicated three major clusters: the shrub-steppe group, the northern group, and the mountain group. The subgeneric classification of Ochotona species needs to be revised because each of the two subgenera in the present classification contains species from the mountain group. To solve this taxonomic problem so that each taxon is monophyletic, i.e., represents a natural clade, Ochotona could be divided into three subgenera, one for the shrub-steppe species, a second for the northern species, and a third for the mountain species. The inferred tree suggests that the differentiation of this genus in the Palearctic Region was closely related to the gradual uplifting of the Tibet (Qinghai-Xizang) Plateau, as hypothesized previously, and that vicariance might have played a major role in the differentiation of this genus on the Plateau, On the other hand, the North American species, O. princeps, is most likely a dispersal event, which might have happened during the Pliocene through the opening of the Bering Strait. The phylogenetic relationships within the shrub-steppe group are worth noting in that instead of a monophyletic shrub-dwelling group, shrub dwellers and steppe dwellers are intermingled with each other. Moreover, the sequence divergence within the sister tars of one steppe? dweller and one shrub dweller is very low. These findings support the hypothesis that pikes have entered the steppe environment several times and that morphological similarities within steppe dwellers were due to convergent evolution. (C) 2000 Academic Press.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Random amplified polymorphic DNA (RAPD) markers are used to investigate genetic variation and evolutionary relationships of 29 samples of Cordyceps sinensis from different geographical populations on the Qinghai-Tibet plateau. Out of 137 RAPD bands scored, 100 are polymorphic. A correlation is revealed between geographical distance and genetic distance. The molecular phylogenetic tree suggests that the 29 samples are divided into three notable clusters, corresponding to the geographical populations, i.e., the north population (NP), middle population (MP), and south population (SP). The NP consists of 7 northern samples from Menyuan, Maqu, and Luqu, the MP consists of 8 samples from Yushu and Chengduo, and the SP consists of 14 samples from Byma Snow Mountain, Renzhi Snow Moutain, Chongcaoxiwa, and Dacaodi. It is demonstrated that extensive genetic diversity is found among different geographical populations of C. sinensis. The genetic diversity pattern of C. sinensis may be caused by the founder effects. The taxonomic status of NP, MP, and SP populations should be that they are different subspecies rather than different species.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Premise of the study: Microsatellite markers were developed for Pinus koraiensis to characterize its genetic diversity and understand its population structure. Methods and Results: Using the Fast Isolation by AFLP of Sequences COntaining (FIASCO) Repeats protocol, 20 primer sets were developed in Chinese populations of P. koraiensis. Three of the markers showed polymorphism with two alleles per locus when assessed in a sample of two populations of P. koraiensis from the Changbai Mountain in the Jilin Province of China. Five and three loci were successfully amplified in P. taiwanensis and P. massoniana, respectively. The amplification size of these loci matches those in P. koraiensis. Conclusions: These markers may be useful for further investigation of population genetics of P. koraiensis.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

By impairing both function and survival, the severe reduction in oxygen availability associated with high-altitude environments is likely to act as an agent of natural selection. We used genomic and candidate gene approaches to search for evidence of such genetic selection. First, a genome-wide allelic differentiation scan (GWADS) comparing indigenous highlanders of the Tibetan Plateau (3,200 3,500 m) with closely related lowland Han revealed a genome-wide significant divergence across eight SNPs located near EPAS1. This gene encodes the transcription factor HIF2 alpha, which stimulates production of red blood cells and thus increases the concentration of hemoglobin in blood. Second, in a separate cohort of Tibetans residing at 4,200 m, we identified 31 EPAS1 SNPs in high linkage disequilibrium that correlated significantly with hemoglobin concentration. The sex-adjusted hemoglobin concentration was, on average, 0.8 g/dL lower in the major allele homozygotes compared with the heterozygotes. These findings were replicated in a third cohort of Tibetans residing at 4,300 m. The alleles associating with lower hemoglobin concentrations were correlated with the signal from the GWADS study and were observed at greatly elevated frequencies in the Tibetan cohorts compared with the Han. High hemoglobin concentrations are a cardinal feature of chronic mountain sickness offering one plausible mechanism for selection. Alternatively, as EPAS1 is pleiotropic in its effects, selection may have operated on some other aspect of the phenotype. Whichever of these explanations is correct, the evidence for genetic selection at the EPAS1 locus from the GWADS study is supported by the replicated studies associating function with the allelic variants.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

2005年9月利用铗日法辅以陷阱法对位于秦岭山脉南坡东段的平河梁自然保护区及牛背梁自然保护区小型兽类进行了调查,共设置采集点10个;2 460铗日中共捕获小型兽类689只,隶属于3目6科19属27种(另有两种鼢鼠和一种鼯鼠系其他手段捕获),平均捕获率28.01%.对捕获的27种小型兽类生态和垂直分布进行分析结果表明:平河梁保护区3个群落的Shannon-Weiner多样性指数在2.9288-3.3639之间,Pielou均匀性指数在0.7669-0.8602之间.在上述调查的基础上,结合前人对邻近地区的调查,据一些物种的分布特点,订出平河梁自然保护区小型兽类的名录,计48种,结果显示秦岭南坡东段小型兽类的物种多样性和丰富度要高于秦岭其他地区.另在考察中采集到白尾鼹(Parascaptor leucura)、小纹背鼩鼱(Sorex bedfordiae)、斯氏鼢鼠(Myospalax smithⅡ)、川西白腹鼠(Niviventer excelsior),在秦岭山区尚属首次记录.还整理了秦岭南坡小型兽类名录,认为秦岭南坡有小型兽类55种,在动物地理区划上应属于西南区.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The western black crested gibbon (Nomascus concolor), or black gibbon, one of the lesser apes (Hylobatidae), is mainly distributed in Yunnan, China. Of the four recognized subspecies, N. c. jingdongensis is endemic to the Wuliang Mountain, central Yunnan,

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The diet of a habituated group of black crested gibbon (Nomascus concolor jingdongensis) was studied from March 2005 to April 2006 in the Wuliang Mountains, central Yunnan, China. Gibbons consumed 77 different plant species, one mammal-, two bird-, one li

Relevância:

10.00% 10.00%

Publicador:

Resumo:

2007-09-05-2007-11-05和2008-09-03-2008-11-07期间,在云南省新平县哀牢山金山丫口(23°57′N,101°30′E)对影响秋季夜间网捕鸟类组成因素进行了调查.主要利用温湿度表和定性观察对各因素进行判断.其研究结果表明,地理特点是影响夜间刚捕鸟类种类的主要因素:气象条件是影响夜间网捕鸟类种类和数量的重要因素.气象条件中的风向、风力、雾以及月相周期对夜间网捕鸟类数量和种类的影响极其显著(P<0.01).风向的影响比风力大,其中,在西南风大雾新月或者存西南风大雾残月期间,夜间网捕鸟类数量和种类最多:光也是夜间网捕鸟类的必要条件.然而,温湿度对夜间网捕鸟类数量和种类影响不显著.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

2007-09-05-2007-11-05和2008-09-03-2008-11-07期间,在云南省新平县哀牢山金山丫口用灯光诱捕对秋季夜间迁徙鸟类组成进行了调查.共捕获鸟类129种,7943只,分属于14日23科.雀形目鸟类为网捕主要鸟类,占总网捕数量的58.9%.其中红尾伯劳(Lanius cristatus)、小杜鹃(Cuculus poliocephalus)和红喉歌鸲(Luscinia calliope)3种是该地夜间网捕优势种鸟类,三者数量皆超过网捕岛类总数的5%.每天夜间20:00-22:00和次日凌晨04:00-4)6:00是捕获鸟类数最的高峰时段.网捕期间,早期Shannon-Wiener指数和Pielou指数最低,优势指数C最高;中期Shannon-Wiener指数和Pielou指数最高,优势度指数C最低.2008与2007年相比,优势指数C和G-F指数较低.但Shannon-Wiener指数和Pielou指数较高.云南省不同"打雀山"仪问捕获鸟类的种类和数量存在差异.地理和气候可能是造成这些差异的主要因素.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Leptobrachium ailaonicum is a vulnerable anuran restricted to a patchy distribution associated with small mountain streams surrounded by forested slopes at mid-elevations (approximately 2000-2600 m) in the subtropical Mount Wuliang and Mount Ailao ranges in southwest China (Yunnan Province) and northern Vietnam. Given high habitat specificity and lack of suitable habitat in lower elevations between these ranges, we hypothesized limited gene flow between populations throughout its range. We used two mitochondrial genes to construct a phylogeographic pattern within this species in order to test our hypothesis. We also examined whether this phylogeographic pattern is a response to past geological events and/or climatic oscillations. A total of 1989 base pairs were obtained from 81 individuals of nine populations yielding 51 unique haplotypes. Both Bayesian and maximum parsimony phylogenetic analyses revealed four deeply divergent and reciprocally monophyletic mtDNA lineages that approximately correspond to four geographical regions separated by deep river valleys. These results suggest a long history of allopatric separation by vicariance. The distinct geographic distributions of four major clades and the estimated divergence time suggest spatial and temporal separations that coincide with climatic and paleogeographic changes following the orogeny and uplift of Mount Ailao during the late Miocene to mid Pliocene in southwest China. At the southern distribution, the presence of two sympatric yet differentiated clades in two areas are interpreted as a result of secondary contact between previously allopatric populations during cooler Pleistocene glacial cycles. Analysis of molecular variance indicates that most of the observed genetic variation occurs among the four regions implying long-term interruption of maternal gene flow, suggesting that L ailaonicum may represent more than one distinct species and should at least be separated into four management units corresponding to these four geographic lineages for conservation. (C) 2009 Elsevier Inc. All rights reserved.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The Yunnan snub-nosed monkey (Rhinopithecus bieti), an endangered species in China, has received more protection in theory than in practice. Therefore it is on the very verge of extinction. The population of the species was estimated less than 2,000 individuals spread in 19 distinct groups. It was confirmed that the monkey was confined to the Yunling Mountain System, the area between the Yangtze River (Changjiang, aka Jinshajiang) to the east and the Mekong River (Lancangjiang) to the west. We further concluded that a lowland belt to the east, about 100 km long and 20 - 30 km wide was not suitable habitat for the monkeys, and appeared to serve as the natural ecogeologic barrier for the species. Our results indicated that the southern limit of the distribution was at Longma (26-degrees 14'N), and that the northern limit of the distribution was at Xiaochangdu (29-degrees 20'N). The distribution area of the species was substantially smaller than previously estimated. There were substantial ecological differences between the southern and northern parts of the species range. The monkey was found only in fir-larch forest.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

在神农架香溪河流域内不同海拔高度沿河岸带共设置42个与河岸方向相同的10 m宽、100 m长样带进行植被调查,发现河岸带分布有珍稀保护植物14种,占神农架地区珍稀植物总数的42.4%,这些珍稀植物主要分布在1200~1800 m山地常绿阔叶林、落叶阔叶混交林带,表明在神农架地区植物群落的物种多样性在中等海拔高度上最大。TWINSPAN分类可把14种珍稀物种可划分为低海拔、中等海拔和较高海拔种组3组,DCA排序也使14种珍稀物种在反映海拔梯度的第一轴可以得到很好的展示。本文还对河岸带珍稀植物分布格局的成因进