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1.
Eleven species of tardigrades in South Georgia, of which two are new to science, were found in samples collected at fifteen localities. The highest number of species was found in moss from a scree field. Twenty species of tardigrades are presently known from South Georgia, but the island remains insufficiently investigated. The species composition is similar to that of southern South America. The high number of cosmopolitan species makes the geographical distribution pattern of the South Georgian tardigrades more similar to that of macrolichens than to that of insects and vascular plants. 相似文献
2.
The Caatinga (dryland) biome of Brazil is experiencing accentuated desertification due to deforestation and inappropriate uses of its natural resources. Studies examining the diversity of filamentous fungi in Caatinga soils are still scarce and the present work was designed to isolate and identify the soil fungi of this biome in the semiarid region of northeastern Brazil. Soil samples were taken at five random sites during the dry and rainy seasons from the soil surface and at depths of 20 cm. A total of 85 species of filamentous fungi were identified, including species of anamorphic fungi (71 species), Zygomycota (8) and Ascomycota (6). The most abundant genera were Aspergillus (28) and Penicillium (18). No significant differences were observed in the numbers of colony forming units in samples taken during either the rainy or dry seasons, or from surface or subsurface soils. Most of the fungi species isolated from caatinga soils were classified as rare. Our results indicate that anamorphic fungi dominate the soil mycobiota in the Brazilian semiarid region, with species of Aspergillus and Penicillium being most common. 相似文献
3.
The importance of the Hell Gate Polynya to marine birds in High Arctic Canada has not been assessed for two decades. Our breeding season surveys in 2002–04 found 19 species of marine birds using the polynya, in annual numbers perhaps reaching 25000 individuals. The site appears to support nationally significant populations of northern fulmar ( Fulmarus glacialis ), Thayer's gull ( Larus thayeri ) and High Arctic brant ( Branta bernida hrota ), as well as locally important numbers of other species including common eiders ( Somateria mollissima borealis ) and black guillemots ( Cepphus grylle ). The polynya may be particularly important for migration, as many species are observed here earlier than elsewhere in the High Arctic. 相似文献
4.
太岳山森林群落物种多样性 总被引：14，自引：2，他引：14
根据 8个样地的调查资料 ,用丰富度指数、多样性指数和均匀度指数对山西太岳山 10个森林群落多样性进行研究 ,结果表明 :1)同一群落不同层次的物种多样性指数存在一定的波动范围 ;不同群落间 ,物种多样性指数也存在差异 ,这种差异与群落所处的演替阶段相关 ;当群落处于演替的顶级阶段时乔、灌、草 3个层次的物种多样性和均匀度指数多为乔木层 <灌木层 <草本层 ;演替先锋阶段和进展阶段多为乔木层 <灌木层 >草本层或乔木层>灌木层 <草本层。 2 )分布在不同海拔高度的森林群落的物种多样性呈连续性波动的变化 ,表现为随海拔高度的增加 ,物种多样性指数呈上升趋势。 3)群落物种多样性在空间上的差异不仅决定于物种丰富度指数 ,更与各物种间的均匀度指数密切相关 ;进而影响不同层次的物种多样性对群落总体物种多样性的贡献 相似文献
5.
Several studies in arid ecosystems have demonstrated that seedling establishment and survival were greater underneath the canopies of shrubs than in the open spaces between shrubs. These results led to the formulation of the hypothesis that seedling recruitment and survival were dependent on the shelter provided by shrub species (nurse-plant hypothesis). Seedling emergence and survival beneath and between the canopies of selected perennial shrub species were investigated at five localities in the Strandveld Succulent Karoo, each dominated by a different shrub species. Seedling emergence and survival were also examined at three localities dominated by annual species. In general, species richness and seedling densities were significantly higher in open areas than underneath shrubs, while seedling survival percentages did not differ significantly between microsites. Therefore, no evidence could be found to support the hypothesis that seedling recruitment and survival were facilitated by the presence of shrub species. Although most species will be able to establish in the absence of shrubs, the presence of woody species may have other advantages when restoring vegetation in mined areas. 相似文献
6.
The influence of elevation, shrub species, and biological soil crust on fertile islands in the Mojave Desert, USA 总被引：4，自引：1，他引：4
We quantified soil nutrients and biological crust cover (bryophytes and lichens) under the canopies of three species of Mojave Desert shrubs and in interspaces between shrubs at three elevations to determine the effects of shrub species, soil crust, and elevation on islands of soil fertility. Means of pH, organic matter, total Kjeldahl nitrogen, nitrogen mineralization, and gravimetric soil moisture are significantly greater in soils under Ambrosia dumosa (Gray) Payne, Larrea tridentata Cov., and Coleogyne ramosissima Torr. than soils from adjacent interspace microhabitats. Although soil moisture and soil organic matter increase by a factor of 1.5 from the low elevation to the high elevation site, the ratio of shrub to interspace concentrations, or the difference in mean soil variables between shrubs and interspaces, is effectively constant and independent of elevation. Total bryophyte and lichen cover is relatively low (24.5%), however, there are 11 species of bryophytes and two species of lichens distributed across three elevations with the highest species richness and cover at the low-elevation site. Bryophyte and lichen cover is correlated with silt but is not related, consistently, to soil nutrients. Overall, the balance of processes controlling spatial aggregation of soil nutrients under shrubs is remarkably insensitive to potential differences in organic inputs among elevations, shrub species, and soil crust surfaces. 相似文献
7.
8.
The contents of regurgitated Long-eared Owls (Asio otus) pellets collected in Minqin Desert Experimental Research Station of northwestern China were analysed. A total of 303 individuals representing five species of rodents and one of bird were identified in the pellets. By frequency, the most common species taken by Long-eared Owls was Meriones meridianus, followed by Cricetulus barabensis and Phodopus roborovskii. By biomass, Meriones meridianus was the most important species taken, followed by C. barabensis and Rhombomys opimus. Our results suggest that the Long-eared Owls were nocturnal hunters and fed on a wide range of animals with respect to their habitats. 相似文献
9.
Assemblages of small bird species (<90 g body mass) from the Monte desert in Argentina were studied to analyze spatial and temporal variation in abundance and species richness. Mean species richness was higher during breeding season than in non-breeding season. The same pattern was observed in aerial insectivores, while granivores and substrate insectivores did not differ between breeding and non-breeding seasons. Overall bird abundance was similar across seasons. Species richness was positively correlated with bird abundance and negatively correlated with dominance; bird abundance and dominance were not correlated. These patterns could be explained by distinct responses of functional groups of birds; dominant species were granivores in the non-breeding season and aerial insectivores during the breeding season, and bird abundance in functional groups changed according to food supply. Most species are residents or regular migrants, while there are few nomadic and transient species. Predictable annual fluctuations in rainfall and resource availability should favor a migratory strategy more than nomadic movements. Similarly, breeding is strongly seasonal and most species start breeding when the first summer rains have generally not yet fallen. Finally, concordances in assemblage structure at local and regional scale suggest that similar mechanisms are acting on the local bird assemblages across the Monte. 相似文献
10.
ABSTRACT. The conceptualization of alien invasive species conflates two axes of variability that have become unhelpfully blurred. The nativeness/alienness axis refers to the presumed belonging of a species in ecological or social space. Invasiveness refers to the behavior of the species in question, particularly in relation to other species. The overlay of nation introduces further variability. Teasing these axes apart is important for more effective environmental management. We examine these concepts using two influential forms of ecological knowledge: the biogeographical and ecological literature and the vernacular experiences of suburban backyarders. Three case studies, the invasive native Pittosporum undulatum and two invasive exotics, Lantana camara and Cinnamomum camphora, illustrate the complex and contingent nature of human interactions with such species and the potential for human interactions to increase and/or reduce the propagation of plant species. 相似文献
11.
TORSTEIN ENGELSKJØN 《Polar research》1987,5(1):79-127
A renewed survey of the flora of Bjornoya (74° 31'N) has yielded a total of 54 native vascular species. Details of their distribution are provided by local maps and vertical frequency tabulations. Soil preferences of species and various plant communities are outlined. The general climate and microthermal conditions of the prevailing vegetation place Bjerneya as a pronouncedly maritime part of the Svalbard archipelago, supporting mainly hygrophilous and chionophilous plant communitites and species. Only half of the island's vascular species persist at elevations above 200 m a.s.l., corresponding to a heat sum of July and August below approximately 190 Degree-Days. Ice-cored peat mounds coated by Rhacomitrium lanuginosum were discovered on plateaux above 400 m elevation.
The impact of the Vistula glaciation is discussed in view of Quaternary evidence from the Barents Sea area. Probably only one third of the present vascular flora could endure full-glacial conditions in possible ice-free cliffs on the coast of Bjornaya. 相似文献
The impact of the Vistula glaciation is discussed in view of Quaternary evidence from the Barents Sea area. Probably only one third of the present vascular flora could endure full-glacial conditions in possible ice-free cliffs on the coast of Bjornaya. 相似文献
12.
建三江农垦分局湿地植物群落分类和排序 总被引：8，自引：1，他引：7
采用双指示种分析（Two Way Indicators Species Analysis,TWINSPAN）和除趋势对应分析（Detrended Correspondence Analysis,DCA）方法,对位于三江平原的建三江农垦分局内的湿地植物群落的数据进行群落数量分类和排序。调查的86个样地中共发现49科133属226个物种;TWINSPAN将样地划分为8种群丛,将优势物种划分为8组,分类结果可以在DCA排序图上很好地反映出来,且优势物种的分布格局很大程度上决定了群丛的分布格局;DCA的前两个排序轴提供了23．5％的信息量,其中第一排序轴提供了14．5％的信息量,主要反映出样地水分条件的变化;样地的排序结果反映了植物群落类型与环境因子之间的关系。 相似文献
13.
How species diversity–productivity relationships respond to temporal dynamics and land use is still not clear in semi-arid grassland
ecosystems. We analyzed seasonal changes of the relationships between vegetation cover, plant density, species richness, and aboveground
biomass in grasslands under grazing and exclosure in the Horqin Sandy Land of northern China. Our results showed that in
grazed and fenced grassland, vegetation cover, richness, and biomass were lower in April than in August, whereas plant density
showed a reverse trend. Vegetation cover during the growing season and biomass in June and August were higher in fenced grassland
than in grazed grassland, whereas plant density in April and June was lower in fenced grassland than in grazed grassland. A negative
relationship between species richness and biomass was found in August in fenced grassland, and in grazed grassland the relationship
between plant density and biomass changed from positive in April to negative in August. The relationship between the density of the
dominant plant species and the total biomass also varied with seasonal changes and land use (grazing and exclosure). These results
suggest that long-term grazing, seasonal changes, and their interaction significantly influence vegetation cover, plant density, and biomass
in grasslands. Plant species competition in fenced grassland results in seasonal changes of the relationship between species richness
and biomass. Long-term grazing also affects seasonal changes of the density and biomass of dominant plant species, which further
affects the seasonal relationship between plant density and biomass in grasslands. Our study demonstrates the importance of temporal
dynamics and land use in understanding the relationship between species richness and ecosystem function. 相似文献
14.
Two sediment cores obtained from the continental shelf of the northern South Shetland Islands, West Antarctica, consist of: an upper unit of silty mud, bioturbated by a sluggish current, and a lower unit of well-sorted, laminated silty mud, attributed to an intensified Polar Slope Current. Geochemical and accelerator mass spectrometry 14 C analyses yielded evidence for a late Holocene increase in sea-ice extent and a decrease in phytoplankton productivity, inferred from a reduction in the total organic carbon content and higher C : N ratios, at approximately 330 years B.P., corresponding to the Little Ice Age. Prior to this, the shelf experienced warmer marine conditions, with greater phytoplankton productivity, inferred from a higher organic carbon content and C : N ratios in the lower unit. The reduced abundance of Weddell Sea ice-edge bloom species ( Chaetoceros resting spores, Fragilariopsis curta and Fragilariopsis cylindrus ) and stratified cold-water species ( Rhizosolenia antennata ) in the upper unit was largely caused by the colder climate. During the cold period, the glacial restriction between the Weddell Sea and the shelf of the northern South Shetland Islands apparently hindered the influx of ice-edge bloom species from the Weddell Sea into the core site. The relative increases in the abundance of Actinocyclus actinochilus and Navicula glaciei , indigenous to the coastal zone of the South Shetland Islands, probably reflects a reduction in the dilution of native species, resulting from the diminished influx of the ice-edge species from the Weddell Sea. We also document the recent reduction of sea-ice cover in the study area in response to recent warming along the Antarctic Peninsula. 相似文献
15.
广东大亚湾石珊瑚群落的分布及动态变化 总被引：2，自引：0，他引：2
2006年6月对位于南海北部亚热带的大亚湾和大鹏湾石珊瑚群落的分布、种类和覆盖率进行了调查,结果显示大亚湾共有石珊瑚24种,以秘密角蜂巢珊瑚(Favites abdita)为优势种,总覆盖率为20%,大鹏湾有石珊瑚21种,以精巧扁脑珊瑚(Platygyra daedalea)为优势种,总覆盖率为7.9%。大亚湾石珊瑚群落健康状况良好,但生长稀疏,群落密度低,空间结构简单,生长带窄;与1964年、1983年、1984年和1991年的调查结果相比,覆盖率从76.6%下降到20%,优势种从枝状的霜鹿角珊瑚(Acropora Pruinosa)转变成块状或皮壳状的秘密角蜂巢珊瑚,群落生态退化严重,主要原因可能是人为破坏活动对珊瑚本身以及生长环境造成的压力所致,包括过度捕捞、盗采珊瑚、沿岸施工和水体污染等,建议采取相应的保护措施。 相似文献
16.
FaradinaMerican WanMaznahWO WanAsmadiWA MashhorMansor 《湿地科学》2007,5(3):243-252
Researches on the Antarctic microalgal diversityand distributions in the freshwater environment ran-ging from snow to large lakes and well-definedstreams are extensive.For instance,studies on thestream microalgal community have been conducted onthe Pervay… 相似文献
17.
We examined the soil microfungal community of the saline Arubotaim Cave, Israel. A total of 68 species from 28 genera were isolated. The most prominent features of the cave mycobiota were: the prevailing number of melanin-containing micromycetes; the abundant presence of the Aspergillus species; a comparatively large share of sexual ascomycetes; and the spatial and temporal variation of the mycobiota composition. Nine species were considered as a characteristic micromycete core for the cave. Many of the micromycetes isolated are distributed worldwide. This confirms the conclusion of many mycologists working in areas with saline and arid soils that there is no specific halophilous mycobiota characteristic for these soils. 相似文献
18.
Given species' vulnerability to climate change, land use change, and habitat loss, it is pertinent to examine how the distribution of a particular species is related to those factors. We assessed the use of climate, habitat, and topography data for modeling the distributions of 14 central European wetland birds, and compared the relative importance of these factors among bird groups with differing latitudinal distributions in Europe. We used the Third Atlas of Breeding Birds in the Czech Republic as a source of species distribution data. Variables were derived from Corine Land Cover, WorldClim, and Shuttle Radar Topography Mission (SRTM) data. Hierarchical partitioning and multiple logistic models identified climatic, topographical, and habitat predictors as important determinants of distribution for each of the species under study. However, the relative contributions of particular variables differed among the species. Climatic, topographical, and habitat factor groups also differed in their importance to latitudinal species groups. Our results indicated that wetland birds with range margins close to the Czech Republic were potentially limited by two different factors: climate conditions impact the southerly distributed species and the availability of suitable habitat affects the northerly distributed species. The accuracy of the study models varied from fair to high (the area under curve values was 0.60–0.89) and revealed negative correlations with the relative occurrence area. In this study, we propose that any difference in model performance is more attributable to data characteristics than to a species' geographical characteristics. 相似文献
19.
The species composition and biomass of material collected in the summers 1981 and 1983 from 69 stations in the Hornsund fiord were analysed. 48 macroalgal taxa were found: 13 green algae, 18 brown algae and 17 red algae. 19 of these taxa were not reported from the nearby Isfjorden.
The overall biomass for the littoral zone varied from 0 to 216gnT2 formalin d.w., although in J of samples the biomass was between 20 and 80 gm_z . The dominant species were Fucus distichus, Acrosiphonia duriusada and Pilayella littoralis.
Using cluster analysis, an attempt was made to delimit regions with a characteristic species composition. The results obtained, however, do not permit this in the littoral zone of the Hornsund fiord. 相似文献
The overall biomass for the littoral zone varied from 0 to 216gnT
Using cluster analysis, an attempt was made to delimit regions with a characteristic species composition. The results obtained, however, do not permit this in the littoral zone of the Hornsund fiord. 相似文献
20.
在2×2联列表的基础上,应用χ2检验、联结系数、spearman秩相关,检测古尔班通古特沙漠植物种间关系,以期分析各物种在沙垄不同地貌部位的变化异同及种群稳定性。结果表明:①灌草两层共435个种对中,联结程度达到显著的种对较少;极显著的有15种对,显著的有22种对,其余398种对联结程度不显著。②按组间联系及种间的正负关联性,将30个主要优势种划分为5个生态种组。灌木层植物可分为3个种组:Ⅰ.白梭梭、沙拐枣;Ⅱ.蛇麻黄;Ⅲ.绢蒿;草本层分为两个种组:Ⅰ.苔草、尖喙牻牛儿苗、条叶庭芥、角果藜;Ⅱ.对节刺、沙生千里光、东方旱麦草;并提出各生态种组物种的分布特征。 相似文献