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1.
目前,关于里海的两个主要问题是水位变化及其生态条件。历史上,里海的海水入侵和衰退对该区域的生活和生产有很大影响。应用地质数据、历史数据和考古数据,以及观测数据,本文对地质历史时期里海水位的变化、年度和季度变化以及短期的波动进行了研究。文章对解释里海水位波动的两种不同的方法进行了论述,并认为里海水位变化是受地质、水文气候和水量平衡以及人类活动等因素的影响的多级过程,其中主要影响因素为水文气候的变化。  相似文献   

2.
里海的国际法状态争执有着深刻的历史渊源。苏联解体后,里海的国际法状态迄今为止仍未解决,争执的内容包括水域划分和渔业通航等问题,矿产资源开发和海底划界、生态安全是里海划界过程中的核心内容。在这一过程中,逐渐形成了新的区域利益集团,这不仅影响该地区安全格局,影响着里海国际法状态的最终解决,也进一步影响着该地区地缘政治经济发展。  相似文献   

3.
Diatom resting spores are a widespread, but sometimes misconstrued component of siliceous microfossil assemblages. We illustrate and discuss resting spore morphology found in populations ofAcanthoceras andUrosolenia, two widely distributed freshwater genera. Taxonomic status of these genera and the potential paleolimnologic interpretation of resting spores are discussed.  相似文献   

4.
During May and June 1991, the biological and ecological features of sixteen aquatic localities in Zhanjiakou region, Hebei, northern China, were investigated. Their salinity ranged from 0.98 to 175.2 g L−1. Fish and benthic macroinvertebrates were depauperate. 116 samples were collected. 91 species (or genera) of phytoplankton and 94 species of zooplankton were recorded. In most of the saline lakes, Cl and Na+ were dominant, and alkalinity and pH values were higher. For phytoplankton, major species wereChroococcus minutus, Oscillatoria tenuis [blue-green algae];Chlamydomonas spp.,Chlorococcus spp.,Chlorella vulgaris, Crucigenia quadrata, Dunaliella salina, Kirchneriella contorta, Oocystis lacustris, Scenedesmus acuminatus [green algae]; andCyclotella meneghiniana, Navicula spp.,Nitzschia spp. [diatoms]. Other phytoplankton taxa present included:Cryptomonas erosa, Chroomonas acuta, Chromulina pascheri, Euglena viridis. For zooplankton, major species included:Vorticella campanula, Epistylis breviramosa, Euplotes terricola [protozoa];Brachionus plicatilis, Hexarthra fennica, Keratella quadrata, Notholca acuminata quadrata [Rotifera];Daphnia magna, D.longispina [‘Cladocera’];Artemia spp. [Anostraca];Arctodiaptomus rectispinosus andCyclops vicinus [Copepoda]. The species composition, distribution, salinity tolerance of planktonic forms in inland saline waters are discussed and their relationship with certain environmental factors.  相似文献   

5.
楚科奇海和白令海浮游植物的种类组成与分布   总被引:15,自引:0,他引:15       下载免费PDF全文
根据 1 999年 7月至 8月我国首次北极科学考察期间“雪龙”号考察船在楚科奇海 ( 66°0 .3′N75°1 8.6′N ,1 5 3°36.5′W 1 74°5 9.5′W )和白令海 ( 5 5°5 9.8′N66°0 .3′N ,1 73°2 1 .1′E1 75°5 3.9′W)采集的 5 1份网采样品和 2 4份水采样品 ,鉴定浮游植物 3个门类 38属 1 2 1种 (含变种和变型 ) ,都是真核藻类。其中楚科奇海有 33属 1 0 3种 ,白令海有 2 5属 71种 ,两海区共有种 49种。这些种类可分为 4个生态类群 :( 1 )北极类群 ;( 2 )北极、亚北极北方类群 ;( 3)北方温带类群 ;( 4 )世界性广温类群等。主要优势种有楚科奇海的格鲁菱形藻 (Nitzschiagrunowii)、诺登海链藻(Thalassiosiranordenskioldi)和聚生角毛藻 (Chaetocerossocialis)等和白令海的西氏细齿状藻(Denticulaseminae)、柔弱菱形藻 (Nitzschiadilicatissima)、成列菱形藻 (N .seriata)和长海毛藻(Thalassiothrixlongissima)等。楚克奇海浮游植物的平均丰度 ( 8.32× 1 0 7个 /m3)远高于白令海( 1 .5 8× 1 0 6个 /m3)。文中还讨论了调查区浮游植物的分布特点及其与环境的关系。  相似文献   

6.
In the Dzhungarian Alatau, a large Asian mountain range, 33 species from the polymorphic genusAlliumL. have been found. They belong to the subgeneraRhizirideum,AlliumandMelanocrommyumand are distributed from the foothills to alpine belts. The geographical and genesis analysis of these species is given. Five species can be ascribed to the category of autochtonous of the region, among them one being endemic to the Dzhungarian Alatau.  相似文献   

7.
周跃泰勒  D 《热带地理》1995,15(4):362-368
加那利群岛位于摩洛哥以西的中大西洋东部海面。群岛种子植物的特有现象十分突出。特有区系历史久远,至今尚保留着旧有的特征。特有种属最集中的月桂林特有植物区系的发展历史可追溯到早第三纪,是当时特提斯海沿岸亚热带植物区系之一部分。许多特有成分受第三纪晚期的冰期活动和撤哈拉地区干旱的影响从古地中海周围伸延到这里来,并且自上岛后便开始了新的进化繁衍历程。特有区系可分为古特有、新特有和变异残余三个类群。  相似文献   

8.
The aim of this study was to determine the water requirements for germination and early seedling establishment of four African savanna tree species, namelyAcacia karroo, A. nilotica, A. tortilisandMundulea sericea. The acacias are characteristic of nutrient-rich, andM. sericeaof nutrient-poor savannas. Imbibition times of scarified seeds ofA. karroo(4 h),M. sericea(6 h) andA. tortilis(8 h) were rapid relative toA. nilotica(28 h) and were inversely correlated with seed size. Imbibed water is lost in about 2 h after drying at 25°C for all species exceptA. nilotica(only 70% moisture loss). Seeds ofA. karrooandM. sericeakept at 40°C dried to below their original moisture contents within 2 h. Seeds ofA. niloticaandA. tortilisdried at 40°C lost viability relative to (undried) control seeds, while there was no significant loss of viability forA. karrooandM. sericea. For fully imbibed seeds to germinate in sandy savanna soils, all four species required at least the equivalent of 3 mm rainfall every 2 days under mild greenhouse conditions. However, most ungerminated seeds were still viable despite drying-out from a fully imbibed state. Maintenance of soil at 50% field capacity (FC), or watering to FC every 9th day is the maintenance requirements for 2-week-old seedlings ofA. niloticaandM. sericeato continue growth for a further 5 weeks under greenhouse conditions, althoughA. niloticamostly survived 25% FC with one seedling surviving 12·5% FC. Root penetration was rapid in sandy soils, withA. niloticaandM. sericeaattaining a depth of 40 cm within 15 days. Frequent, but not necessarily high, rainfall appears to be essential for germination and seedling survival over the first 7 weeks.  相似文献   

9.
This article considers public opinion in the republic of Dagestan on the expansion of hydrocarbon production in the Russian sector of the Caspian Sea. The article reports the findings of a survey (N = 956) conducted in 2010 in fourteen rural locations in the republic. Overall, respondents uniformly oppose the proposed expansion of offshore oil and gas production in the Russian sector of the Caspian Sea, seeing little economic benefit from this development and expressing concern about the environmental consequences. These findings resonate with work in geography on resource peripheries and development alternatives available in these locations.  相似文献   

10.
Krameria lappacea (Rhatany or Ratanhia, Krameriaceae) is an endangered, overexploited medicinal plant from the semi-deserts of Andean South America, and is destructively harvested from nature. There are published data on parasitism of Krameria from three North American species, but not on K. lappacea, the only economically important species. The present study investigates the presence or absence of hemiparasitism, host plant range and haustorium morphology/anatomy. The study was carried out at two sites in Peru, Department Arequipa, Prov. Arequipa. Hemiparasitism was confirmed, with 106 haustorical connections to 18 host plant species from 17 genera and 12 plant families observed, nearly doubling the number of host plant species known for Krameria (incl. four additional angiosperm families). Root and haustorium architecture and anatomy were found to be similar to the North American species. K. lappacea is a highly generalistic hemiparasite and host distribution and abundance are likely not limiting factors for Krameria recruitment and establishment. Due to its wide range of host plants K. lappacea likely influences the performance of the bulk of perennial species in its habitat and overcollection affects the overall vegetation. Conservation strategies and adequate management should have high priority because of the likely ecological and known economical importance of this species.  相似文献   

11.
安徽种子植物特有属的生物多样性及其保护   总被引:1,自引:0,他引:1  
论述了安徽种子植物特有属的物种组成多样性、生态类型多样性、空间分布格局多样性及其生态地理特性和区系特征,探讨了安徽与邻近地区中国种子植物特有属的地理联系及其重要地位,并对特有属的生物多样性保护与持续发展提出了具体对策.  相似文献   

12.
Data on benthic macroinvertebrates of the northern Caspian Sea in 1980–1991 were collected by the Caspian Fishery Research Institute. During the initial period of the water-level rise, the main trends in benthic macroinvertebrates were increases in the biomass of the main groups and decreases in the relative abundance of species of Mediterranean origin. There was no significant alteration in species composition. The increased abundance was due to improved trophic conditions and a decrease in the numbers of benthos-feeding fish. Some decrease in the relative abundance of species of marine origin was related to a decrease in water salinity.  相似文献   

13.
150年来青藏高原南红山湖的介形类与环境变化   总被引:14,自引:1,他引:14  
青藏高原西北部南红山湖2孔湖芯沉积物中的介形类动物群计有4属4种,据其分布特征划分出5个组合,各组合间的差异表现在介形类动物群丰度和每个种的丰度变化以及特征种的出现。通过分析介形类属种生态特征和组合变化对150年来的南红山湖环境变化进行了探讨。分析结果表明:1884年前为有缓慢水流注入的滨岸浅水期;1885~1970年间为湖水相对温暖期,在这期间湖泊环境仍有次一级的变化,其中,1885~1905年湖面迅速抬升,水深增大,水温也较高,1923~1944年为湖水温度另一个稍高期,1961~1969年湖面再次出现明显上升;1970年以来湖泊退缩、咸化。  相似文献   

14.
里海地区能源安全及西方对该地区的地缘政治战略   总被引:1,自引:0,他引:1  
里海地处欧亚大陆的接合处,地理位置极其重要。近年来,随着一批新的里海大型油汽田的探明,里海的石油地位也迅速上升,再次成为世界关注的焦点。苏联解体后,里海地区一方面因其丰富的油气资源储备备受国际社会关注;另一方面,里海面临着激烈的国际竞争局面和不稳定的区域发展前景。本文论述了里海地区油气资源的储备和生产、出口现状以及国际竞争的局面,尤其是西方参与里海地区油气资源竞争的格局,这不仅引起该地区非国家主体的地缘政治的改变,从而也深刻影响着西方国家主体对该地区的战略和政策。  相似文献   

15.
横断山区植物区系的基本特点为,植物种类多,古老植物多,特有植物多,地理成分复杂,各地理成分联系复杂,植物分化强烈。  相似文献   

16.
Five captive adult female degus (Octodon degus) were offered leaves and twigs to eat from three woody (Adesmia bedwellii,Porlieria chilensisandProustia pungens) and two suffruticose (Baccharis paniculataandChenopodium petiolase) shrubs that provide cover in their natural habitat. The degus discriminated among the plant species, consuming lower amounts ofP. chilensis. Daily body mass losses of degus were significantly higher when they were fed uponP. pungensandP. chilensis. The nutritional value of plants, concomitant with degu nutritional requirements, may explain changes in shrub cover previously found to follow removal of degus from experimental plots.  相似文献   

17.
Wetland parks play various ecological roles, including maintaining regional ecological balance, and connoting and compensating water sources. Taking Harbin Qunli National Urban Wetland Park as the research object, the diversity of plant resources in wetland parks is investigated and analyzed with the goal of providing a scientific basis for ecological restoration and the conservation and utilization of urban wetlands. Field survey, sampling and data collection methods were used to study the wetland plant resources and their life types (e.g., vines or shrubs), ecological types and distribution types. The study found 60 families, 129 genera and 160 species of wetland plants in Qunli National Urban Wetland Park, including 56 families, 123 genera and 151 species of angiosperms, which include 48 families, 101 genera and 127 species of dicotyledons and 8 families, 22 genera and 24 species of monocotyledons; 2 families, 2 genera and 3 species of ferns; and 2 families, 4 genera and 6 species of gymnosperms. The family composition is dominated by those families that included 10 or more species, and the dominant families are Compositae and Rosaceae. The genus composition is dominated by genera with four or more species present, and the dominant genera are Acer, Malus and Artemisia. Among the six life types, herbaceous plants are dominant, with a proportion of 62.50% of the species. The ecological types are divided into three categories: wet, mesophytic and aquatic plants, with wet plants accounting for the largest proportion, i.e., 56.25% of the total number of plant species. There are five distribution types of plant families and 10 types of the genera, with both families and genera dominated by the Northern Temperate types, so the flora has obvious temperate characteristics.  相似文献   

18.
Extensive areas of low lying coastal plains on Santiago Island, Republic of Cape Verde, are virtually devoid of natural vegetation. Of many introduced trees and shrubs, onlyAtriplexspecies have been found to thrive. Several plantations have been established during the past 15 years by the Cape Verde Government, FAO and other agricultural development groups. Results from these, together with local perceptions, indicate that although growth and survival are good, the primary objective of providing forage is not being met, owing to the unpalatability ofAtriplexto local stock. In recent field trials, severalAtriplexspecies showed good growth, but none were browsed and survival was quite poor, with onlyA. undulata(65%) andA. canescens(100%) exceeding 60% survival. Forage analysis identified high salt content in all species tested, and the highest protein content was found inA. glauca(16%),A. vesicaria(17%) andA. canescens(20%), which also had the lowest salt levels.Atriptex canescenswas identified as worthy of further introduction. An establishedA. halimusplantation that was observed to be browsed was compared to unbrowsed stands in terms of forage, soil and local drinking water analyses. Possible reasons for the unpalatability ofAtriplexto local stock and its resolution are discussed, along with the potential future ofAtriplexon the Cape Verde Islands.  相似文献   

19.
We compared physiological and morphological traits of Thymus loscosii, a rare endemic of semiarid Spain, and Thymus vulgaris, a widespread Mediterranean species, over a precipitation gradient, and measured the spatial patterns of both species. Our results do not provide evidence for a congruent suite of traits associated with rarity in T. loscosii, since this species showed some traits reported in rare species (lower height and biomass), but exhibited better performance under severe climatic conditions (higher photochemical efficiency and quantum yield during winter) and higher values of traits conferring competitive abilities (SLA and LAR). T. loscosii did not show either lower phenotypic variability or better performance than its congener along the precipitation gradient. The two thymes were spatially dissociated when they co-occurred and the spatial pattern of T. loscosii changed from clumped in the presence of its congener to random when it was the only thyme, suggesting competition between the two species. These results suggest that T. loscosii is not a habitat-specialist and may behave as a refuge endemic. Its reduced distribution may be linked to a limited competitive ability that is not associated with the vegetative traits explored, although other causes like habitat degradation and genetic or reproductive constraints might also be important to explain its limited distribution.  相似文献   

20.
The horizontal distribution of the epipelagic zooplankton communities in the western Arctic Ocean was studied during August–October 2008. Zooplankton abundance and biomass were higher in the Chukchi Sea, and ranged from 3,000 to 274,000 ind. m?2 and 5–678 g WM m?2, respectively. Copepods were the most dominant taxa and comprised 37?94% of zooplankton abundance. For calanoid copepods, 30 species belonging to 20 genera were identified. Based on the copepod abundance, their communities were classified into three groups using a cluster analysis. The horizontal distribution of each group was well synchronized with depth zones, defined here as Shelf, Slope and Basin. Neritic Pacific copepods were the dominant species in the Shelf zone. Arctic copepods were substantially greater in the Slope zone than the other regions. Mesopelagic copepods were greater in the Basin zone than the other regions. Stage compositions of large-sized Arctic copepods (Calanus glacialis and Metridia longa) were characterized by the dominance of late copepodid stages in the Basin. Both the abundance and stage compositions of large copepods corresponded well with Chl. a concentrations in each region, with high Chl. a in the Shelf and Slope supporting reproduction of copepods resulting in high abundance dominated by early copepodid stages.  相似文献   

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