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1.

The Xinjiang Uygur Autonomous Region covers nearly 1/6 territory of China, with various landscape patterns, environmental conditions and three key regions of biodiversity of China. The ecosystem here has a relatively simple structure and fragile ecological stability. The coverage of sparse vegetation here is only 2.1% which is far lower than 14%, the average coverage all over the country. Although the fragile and unstable ecosystems are improved partly in the past, the total situation in Xinjiang has worsened (such as drying up of rivers and lakes, desertification and salinization of soil, deterioration of meadow, reduction of biodiversity, etc.). Although the species numbers of Xinjiang are few, the diversity of taxa is very high. The types of plant communities are abundant, and the flora abounds in one-species genus, one-genus family and few-species genus. Also, the fauna abounds in endangered species and endemic species, of which 108 species of vertebrates were listed as nationally protected species. In addition, there are abundant anti-adversity gene pools. The present paper puts forwards several suggestions for biodiversity conservation in Xinjiang.

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2.
The fossil plant female reproductive organs each with a tricarpous were collected from the Yixian Formation, Chaoyang district, western Liaoning Province. The geological age of the Yixian Formation here is believed to be Late Jurassic, which places this fossil as the oldest angiosperm currently known. Its morphological characters are distinct from other known angiosperm reproductive organs as it has 3 ovaries, each with a terminal style and an apical stigma. 9 such organs compose a cyme. As this morphological arrangement is unique to this plant, a new genus and species has been established, namedChaoyangia liangii gen. et sp. nov. Project supported by the Special Finances of Biological Sciences and Technology, Chinese Academy of Sciences (the special item of the Ministry of Finance of the People’s Republic of China).  相似文献   

3.
Although the history of Cambrian conodont study goes back to a century ago, it was not until 1959 that the systematic study of Cambrian conodonts was initi-ated[1]. During the last 44 years Cambrian conodonts have been well documented from all continents but Africa. However, the morphological evolution of para- conodonts and protoconodonts have been subjected to less study than the primitive euconodonts in the inter-val across the Cambrian-Ordovician boundary. Miller (1984) proposed a Weste…  相似文献   

4.
The role of ground water in arid/semiarid ecosystems, Northwest China   总被引:3,自引:0,他引:3  
Cui Y  Shao J 《Ground water》2005,43(4):471-477
Ground water plays an important role in water supply and the ecology of arid to semiarid areas such as Northwest China, where the landscape is fragile due to frequent drought in the past few decades. This paper discusses the role of ground water in these ecosystems, including the effect of condensation water and water table depth on the growth of plants and degree of soil salinity. The paper also discusses the controlling process for land desertification and soil salinization in Northwest China. Water table depth is a key factor controlling the water balance, ground water flow, and salt transport in the vadose zone. The suitable water table depth for vegetation growth, which can prevent land desertification and soil salinization, is within a range of 2 to 4 m; the optimal depth is approximately 3 m. As examples, changes in ecosystems owing to water resources development in Tarim and Manas basins, Xinjiang, China, are discussed.  相似文献   

5.
Four araphid diatom taxa were collected from Florida streams and studied with both light microscopy (LM) and scanning electron microscopy (SEM). Three taxa, formerly in the genus Fragilaria Lyngbye, are here placed in the genus Pseudostaurosira Williams et Round. On the basis of ultrastructure observed by SEM, the remaining taxon is placed in a new genus, Sarcophagodes. At least two of the species referred to Pseudostaurosira may have been confused with species of the genus Opephora Petit, which may have led to misinterpretation of the ecological characteristics of the latter genus.All the taxa treated here belong to the Family Fragilariaceae Greville as delimited in current classification schemes. Two new combinations Pseudostaurosiropsis geocollegarum (=Fragilaria geocollegarum Witkowski et Lange-Bertalot), Pseudostaurosira neoelliptica (=Fragilaria neoelliptica Witkowski) and the new species Pseudostaurosira clavatum are presented herein. Additionally, a new genus, Sarcophagodes, is erected to accommodate the new species S. delicatula. LM and SEM details, as well as criteria delimiting these taxa are discussed. More collections and further analyses are needed to assess the distribution of both Opephora and Sarcophagodes.  相似文献   

6.
中国濒危淡水鱼类致危成因分析   总被引:4,自引:0,他引:4  
乐佩琦 《湖泊科学》1995,7(3):271-276
中国1000多种淡水鱼类因受水工建设、围湖造田、乱伐滥垦等改变和破坏水域环境、酷渔滥捕,水体污染,不合理引种,法制不全及执法不力等原因导致部分鱼类濒危。初步确定为92种,分属9目,24科,78属,根据程度分为四个等级,绝灭4种,稀土23种,濒危28种,渐危37种。  相似文献   

7.
A new species of Tsaidamotherium(Bovidae,Artiodactyla),T.brevirostrum,described here represents only the second discovery of the genus.Tsaidamotherium is a mid-sized late Miocene bovid with an odd-looking plate-like horn-core apparatus so far known only from northwestern China.The holotype of T.brevirostrum is a cranial part of skull from the Liushu Formation(late Miocene)of the Linxia Basin.The new species differs from the type species,T.bohlini,mainly in horn-core morphology,having the frontal horn-cores proper much smaller and less distinctly separated from the plate-shaped posterior portion.Furthermore,the new species has smaller frontal sinuses,but a thicker layer of compact bone beneath the horn-core apparatus as seen in frontal section.A complete skull with a smaller horn-core apparatus is considered to represent a female individual of T.brevirostrum.The facial part of the skull,which is first known for this genus,is very short and high,with a high nasal cavity,strongly retracted nasals,and shortened premaxillae and premolar rows.All this probably suggests that the animal with an enlarged nasal cavity,like the modern Saiga and Budorcas,may have had a special adaptation to the high plateau environment.  相似文献   

8.
Devonian cutinitic liptobiolith is a special cuticle-rich coal formed during the early stage of land plant evolution. In China, this special coal has previously only been reported in the Yangtze area, with the Luquan Devonian cutinitic liptobiolith of Yunnan Province being the most well-known. Recently, this type of coal was first discovered in the Bulonggoer Sag, to the northwest of the Junggar Basin, NW Xinjiang. Its geological age is regarded as the Givetian period of the late Middle Devonian,which is equivalent to the age of the Luquan Devonian coal. The cutinitic liptobiolith from NW Xinjiang has a distinct sheet-like texture resembling a stack of paper or leaf sheets in appearance, and so it is commonly called "paper coal" or "leaf coal". Ribbonlike cutinite(thick-walled type) is the most abundant maceral in the coal(>60% and up to 80%, on a mineral-free basis), followed by ribbon-like collotelinite. The NW Xinjiang and Luquan cutinitic liptobioliths share similar maceral compositions;while their coal-forming plants and depositional conditions are distinct. The NW Xinjiang cutinitic liptobiolith was deposited in a regional fluvial or flood plain condition, with lycopsids as the dominant coal-forming plants. In contrast, the Luquan cutinitic liptobiolith formed in a coastal-lagoon environment, with primitive ferns as the predominant coal-forming plants, followed by lycopsids. The saturated fractions of the NW Xinjiang and Luquan liptobioliths are mainly composed of tetracyclic diterpanes. However, the tetracyclic diterpane compositions in the NW Xinjiang cutinitic liptobiolith are distinct from those in the Luquan Devonian coal:The former is dominated by atisanes and the latter is mainly composed of phyllocladanes. Different coal-forming plants may have contributed to the distinct tetracyclic diterpane compositions.  相似文献   

9.
Biological invasions in marine environment are the lesser known aspect of global change. However, recent events which occurred in the Mediterranean Sea demonstrate that they represent a serious ecological and economical menace leading to biodiversity loss, ecosystem unbalancing, fishery and tourism impairment. In this paper we review marine bioinvasions using examples taken from the Mediterranean/Black Sea region. Particular attention is given to the environmental status of the receiving area as a fundamental pre-requisite for the colonisation success of alien species. The spread of the tropical algae belonging to the genus Caulerpa in the northwestern basin of the Mediterranean Sea has been facilitated by pre-existing conditions of instability of the Posidonia oceanica endemic ecosystem in relation to stress of both natural and anthropogenic origin. Human interventions caused long-term modification in the Black Sea environment, preparing a fertile ground for mass bioinvasion of aquatic nuisance species which, in some cases, altered the original equilibrium of the entire basin. Finally, the Venice lagoon is presented as the third example of an environment subjected to high propagule pressure and anthropogenic forcing and bearing the higher "diversity" of non-indigenous species compared to the other Mediterranean lagoons. Stressed environments are easily colonised by alien species; understanding the links between human and natural disturbance and massive development of non-indigenous species will help prevent marine bioinvasions, that are already favoured by global oceanic trade.  相似文献   

10.
ntroductionGeneralyweregardthevariablepartsofprecursorydatafromwhichthedisturbancesandtheobservationalerorshavebeenremovedast...  相似文献   

11.
目前,世界报道乌龙藻属有11个种类,中国报道2种,但属种特征的描述比较模糊,尤其是其模式种仍被归在其他属.根据采自国内的野外藻类样品和分离纯化培养的藻株,对中国分布的乌龙藻属及其模式种赖格乌龙藻(Woronichi-nia naegeliana(Unger)Elenkin,1933)的形态特征进行了观察和描述,并对它们...  相似文献   

12.
新疆是我国大陆地区开展年度地震趋势预测最早的省区之一,自1973年以来累计划定105个年度地震危险区。整理总结新疆年度地震危险区的时、空分布及地震对应情况,结果表明年度地震预测总报准率为26%,相当于全国的平均预测水平;年度危险区预测数量与预测面积基本成正比;危险区划定次数最多的构造区域是北天山中西段,以下依次是柯枰块区、乌恰-喀什地区、南天山东段、乌鲁木齐地区、西昆仑地区和阿勒泰-富蕴地区,其中北天山中西段和乌恰-喀什危险区的时、空继承性较强,但预测效果相对较差。对新疆年度地震危险区的历史资料进行整理和总结,能为今后更好地提高新疆年度预测水平积累一些参考经验。  相似文献   

13.
Abstract Desmostylians from the Pacific coasts of Japan and North America are compared and taxonomy and adaptations in the mammalian order Desmostylia discussed. The taxonomy is based mainly on teeth and skulls. Feeding adaptations and habitat are discussed using teeth and restored skeletons, respectively. In the extinct order two families, six genera and 10 species can now be recognized. Each genus is distinguished by a set of tooth characters. The three species of the genus Paleoparadoxia have different body sizes. Two species of the genus Desmostylus can be distinguished on morphological differences in the cranium. As a result it is clear that both species, D. hesperus , which had long been recognized only in North America, and D. japonicus , which has hitherto been recognized only in Japan, inhabited both coasts of the Pacific. All genera of the Order Desmostylia share a common and distinctive body form, interpreted by Inuzuka as having a laterally placed limb posture. Based on this body form, the optimum habitat is thought to have been an intertidal sandy beach. The dental morphology is variable, and derived species show an adaptation for wear by an abrasive diet. In conclusion, we theorize that the Order Desmostylia was adapted for a coastal habitat from its inception, with each genus adapting to a different sort of herbivorous diet.  相似文献   

14.
持续时间震级是常规震级类型之一,主要适用于区域地震台网。目前,国内多个地区已有持续时间震级经验公式,但中小地震频繁的新疆地区却没有较适用的经验公式。为了更好地把握新疆地区中小地震的震级,使用新疆测震台网数据,利用地震波形振动持续时间估算震级,对新疆地区2019年8月—2020年12月发生的225个M 2.0—4.0中小地震事件进行统计分析,将各事件持续时间与震级进行散点分析及对数拟合,得到新疆地区持续时间—震级规律与经验公式以及震级与持续时间的对照表。  相似文献   

15.
Ecosystem in the karst region of southwest China is very fragile due to a very limited amount of water storage for plant uptake in the thin and rocky soils underlain by rock fractures. Plants in these karst regions are thought to take water from the soils and shallow fractured rock zone (subcutaneous zone) as well. However, the role of subcutaneous water in maintaining karst vegetation remains unclear, and proportions of the water sources for plant uptake in different environment conditions are unknown. In this study, five typical species of plants at two sites were selected in a karst plateau of Qingzhen, central Guizhou Province of China. Proportions of the possible water sources contributed for the plant uptake from two soil layers and subcutaneous zone were determined on the basis of δD and δ18O values of plant stem water, soil water and subcutaneous water. The analysis reveals that most plants take water from the soil layers and the subcutaneous zone as well, but proportions of these water contributions for plant uptake vary seasonally and depend on site‐specific conditions and plant species. Plant uptake of the subcutaneous water for all species averages less than 30% of the total monthly amount in June and September, compared with more than 60% in dry December. Plants tend to take a larger proportion of water from the upper soil layer at the bush site than at the forest site in June and September (63 vs 28% in July; 66 vs 54% in September for all species in average). In December, however, 98% of water is taken from the subcutaneous zone at the bush site which is much greater than 68% at the forest site. Compared to deciduous arbor, evergreen shrub takes a greater proportion of subcutaneous water in the December drought. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

16.
17.
Abstract Fossil pinnipeds in the extinct otariid subfamily Allodesminae are large, relatively highly evolved marine carnivores that became abundant and diverse in Middle Miocene time and were restricted to the North Pacific Ocean. Their record extends from early Middle Miocene through Late Miocene, with records from California, Oregon, Washington, Baja California and Japan. Allodesmines are characterized by extreme sexual dimorphism, a large orbit, retracted orbital margin of the zygomatic arch, a deeply mortised jugal-squamosal junction, wide palate, bulbous cheek tooth crowns, nearly flat tympanic bulla with wrinkled ventral surface, a large tympanohyal fossa, large ear ossicles and deep mandible. Eleven allodesmine species are known (eight of which are named), in at least four genera, and most belong to the typical genus Allodesmus Kellogg, 1922. The earliest and most generalized allodesmine known is from the early Middle Miocene (ca 16 Ma) Astoria Formation in coastal Oregon. The last known records are from Late Miocene rocks (ca 10 Ma) in California and Washington. New taxa proposed here are: the genus Brachyallodesmus Barnes and Hirota, to contain Allodesmus packardi Barnes, 1972; the genus Megagomphos Hirota and Barnes, to contain Allodesmus sinanoensis (Nagao, 1941); the species Allodesmus sadoensis Hirota, (Middle Miocene, Japan); the species Allodesmus megallos Hirota (Middle Miocene, Japan); and the species Allodesmus gracilis Barnes (Middle Miocene, California). Additionally, the genus Atopotarus Downs, 1956, and the species Allodesmus kelloggi Mitchell, 1966, are resurrected. Allodesmines were apparently a rapidly evolving group, and most appear to have been adapted to roles later filled by otariine, dusignathine and imagotariine otariids, and the Phocidae (true seals). They became extinct in Late Miocene time and left no living descendants. Although some of their characters evolved convergently with various living species of the pinniped family Phocidae, Allodesminae are an otariid group and not part of the evolutionary history of Phocidae.  相似文献   

18.
南疆博斯腾湖末次冰消期新仙女木事件的记录   总被引:4,自引:0,他引:4  
钟巍 《湖泊科学》1999,11(1):28-32
通过对ZK2孔多环境代用指标的综合分析,重建了4500年来鄱阳湖湖口地区古环境历史。研究表明:4500aBP以来,鄱阳湖湖口地区经历了多次冷暖,干湿交替。  相似文献   

19.
近百年来亚洲中部内陆湖泊演变及其原因分析   总被引:7,自引:1,他引:6  
秦伯强 《湖泊科学》1999,11(1):11-19
南疆博斯腾湖湖相沉积物碳酸盐稳定同位素,孢粉及地化元素含量的波动揭示了于11.0 ̄10.0kaBP期间的相对冷湿的环境特征,这次变冷事件在年代上可与末次冰消期的新仙女木气候突然变冷事件相对应,虽然目前还无法圆满解释此事件的成因机制,但此事件在极端干昌的南疆博斯腾湖湖相沉积中的发现,无疑对深入认识此事件发生的全球性以及探讨其成因机制具有重要意义。  相似文献   

20.
IntroductionSinceaMs=6.9earthquakeoccurredinArtux,Xinjiang,ChinaonMarchl9,l996,7earth-quakeswithmagnitudeofMs>6werefollowedsuccessivelynearbyJiashi,southemnanshan.Thephenomenonthatagroupofstrongearthquakes(Jiashiearthquakeswann)concentratedwithinashorterperiodoflyearormoreisanunprecedentedeventsincetheinstrUmentalrecordofseis-micityinthecontinent,drawingconsiderableattentionofseismologists.TheJiashiearthquakeswarmhaPpenedonthenortheastemflankofthewestCmsyntaxofHimalayancollisionbeltwheret…  相似文献   

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