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1.
Diversity is mainly determined by climate and environment. In addition, topography is a complex factor, and the relationship between topography and biodiversity is still poorly understood. To understand the role of topography, i.e., altitude and slope, in biodiversity, we selected Jinggangshan Mountain (JGM), an area with unique topography, as the study area. We surveyed plant and animal species richness of JGM and compared the biodiversity and the main geographic characteristics of JGM with the adjacent 4 mountains. Gleason’s richness index was calculated to assess the diversity of species. In total, 2958 spermatophyte species, 418 bryophyte species, 355 pteridophyte species and 493 species of vertebrate animals were recorded in this survey. In general, the JGM biodiversity was higher than that of the adjacent mountains. Regarding topographic characteristics, 77% of JGM’s area was in the mid-altitude region and approximately 40% of JGM’s area was in the 10°–20° slope range, which may support more vegetation types in JGM area and make it a biodiversity hotspot. It should be noted that although the impact of topography on biodiversity was substantial, climate is still a more general factor driving the formation and maintenance of higher biodiversity. Topographic conditions can create microclimates, and both climatic and topographic conditions contribute to the formation of high biodiversity in JGM.  相似文献   

2.
The association between climate variability and episodic events, such as the antecedent moisture conditions prior to wildfire or the cooling following volcanic eruptions, is commonly assessed using Superposed Epoch Analysis (SEA). In SEA the epochal response is typically calculated as the average climate conditions prior to and following all event years or their deviation from climatology. However, the magnitude and significance of the inferred climate association may be sensitive to the selection or omission of individual key years, potentially resulting in a biased assessment of the relationship between these events and climate. Here we describe and test a modified double-bootstrap SEA that generates multiple unique draws of the key years and evaluates the sign, magnitude, and significance of event-climate relationships within a probabilistic framework. This multiple resampling helps quantify multiple uncertainties inherent in conventional applications of SEA within dendrochronology and paleoclimatology. We demonstrate our modified SEA by evaluating the volcanic cooling signal in a Northern Hemisphere tree-ring temperature reconstruction and the link between drought and wildfire events in the western United States. Finally, we make our Matlab and R code available to be adapted for future SEA applications.  相似文献   

3.
The wetland ecosystem is particularly vulnerable to hydrological and climate changes. The Great Xing’an Mountain is such a region in China that has a large area of wetlands with rare human disturbance. The predictions of the global circulation model CGCM3 (the third-generation coupled global climate model from the Canadian Centre for Climate Modeling and Analysis) indicated that the temperature in The Great Xing’an Mountain will rise by 2–4°C over the next 100 years. This paper predicts the potential distributions of wetlands in this area under the current and warming climate conditions. This predication was performed by the Random Forests model, with 18 environmental variables, which will reflect the climate and topography conditions. The model has been proven to have a great prediction ability. The wetland distributions are primarily topography-driven in the Great Xing’an Mountains. Mean annual temperature, warmness index, and potential evapotranspiration ratio are the most important climatic factors in wetland distributions. The model predictions for three future climate scenarios show that the wetland area tends to decrease, and higher emission will also cause more drastic shrinkage of wetland distributions. About 30% of the wetland area will disappear by 2050. The area will decrease 62.47, 76.90, and 85.83%, respectively, under CGCM3-B1, CGCM3-A1B, and CGCM3-A2 by 2100. As for spatial allocation, wetlands may begin to disappear from the sides to the center and south to north under a warming climate. Under CGCM3-B1, the loss of wetlands may mainly occur in the south hills with flatter terrain, and some may occur in the north hills and intermontane plains. Under CGCM3-A1B, severe vanish of wetlands is predicted. Under CGCM3-A2, only a small area of wetlands may remain in the north of the high mountains.  相似文献   

4.
乐东县位于海南岛西南部,全县呈盆地状的地貌,背山面海,具有山地,丘陵,台地和平原等地貌类型。气候为季风热带气候,终年高温,有明显干、湿季之分,年雨量比全岛的年雨偏少,只有1000一1600毫米,蒸发量大,环境干热。山地则具较湿凉的山地气候特点。全县植被包括各种典型的热带植被。其地带性植被类型为常绿季雨林。同时这里也分布着本岛最典型的热带落叶季雨林。山地上还有沟谷雨林、山地雨林和山顶矮林等,台地上有草原、灌木草丛、刺灌丛及滨海砂生植被等。根据各种植被类型的组合形式和地理分布的特点,以及植被改造、利用方向的一致性,将本县划分为4个植被区和9个植被亚区。并从植被的角度提出森林的保护和垦殖利用问题。  相似文献   

5.
Aim Anthropogenic climate change is expected to result in the complete loss of glaciers from the high mountains of tropical Africa, with profound impacts on the hydrology and ecology of unique tropical cold‐water lakes located downstream from them. This study examines the biodiversity of Chironomidae (Insecta: Diptera) communities in these scarce Afroalpine lake systems, in order to determine their uniqueness in relation to lowland African lakes and alpine lakes in temperate regions, and to evaluate the potential of Afroalpine Chironomidae as biological indicators to monitor future changes in the ecological integrity of their habitat. Location Mount Kenya (Kenya) and Rwenzori Mountains (Uganda). Methods The species composition of Afroalpine chironomid communities was assessed using recent larval death assemblages extracted from the surface sediments of 11 high‐mountain lakes between 2900 and 4575 m. Results were compared with similar faunal data from 68 East African lakes at low and middle elevation (750–2760 m), and with literature records of Chironomidae species distribution in sub‐Saharan Africa, the Palaearctic region and elsewhere. All recovered taxa were fully described and illustrated. Results The 11‐lake analysis yielded 1744 subfossil chironomid larvae belonging to 16 distinct taxa of full‐grown larvae, and three taxa of less differentiated juveniles. Eleven of these 16 are not known to occur in African lakes at lower elevation, and eight taxa (or 50% of total species richness) appear restricted to the specific habitat of cold lakes above 3900 m, where night‐time freezing is frequent year‐round. The faunal transition zone coincides broadly with the Ericaceous zone of terrestrial vegetation (c. 3000–4000 m). Snowline depression during the Quaternary ice ages must have facilitated dispersion of cold‐stenothermous species among the high mountains of equatorial East Africa, but less so from or to the Palaearctic region via the Ethiopian highlands. Main conclusions Chironomid communities in glacier‐fed lakes on Africa's highest mountains are highly distinct from those of lowland African lakes, and potentially unique on a continental scale. By virtue of excellent preservation and their spatial and temporal integration of local community dynamics, chironomid larval death assemblages extracted from surface sediments are powerful biological indicators for monitoring the hydrological and ecological changes associated with the current retreat and loss of Africa's glaciers.  相似文献   

6.
Meteorological and climatic processes in mountain regions play a key role in many environmental systems, in particular the quantity and quality of water that influences both aquatic ecosystems and economic systems often far beyond the boundaries of the mountains themselves. This paper will provide a general overview of some of the particular characteristics of mountain weather and climate, to highlight some of the unique atmospheric features that are associated with regions of complex topography. The second part of the paper will focus upon characteristics of climate and climatic change in the European Alps, a region with a wealth of high quality data that allows an assessment on how climate and dependent environmental systems have evolved in the course of the 20th century and how alpine climate may undergo further changes to “global warming” in the 21st century, as the atmosphere responds to increasing levels of greenhouse gases that are expected in coming decades.  相似文献   

7.
Summary The phytoplankton of three Ceylon lakes, two situated in the warm lowlands and one in the cool mountains has been investigated. Certain similarities and differences in regard to growth, distribution and periodicity of the plankton algae are discussed and related to environmental conditions.The lowland lakes are dominated by Myxophyceae which form 95% and 87% of the phytoplankton respectively, while in the mountain lake, which is temperate rather than tropical, Diatoms form 65% of the phytoplankton. Of the lowland lakes that in the centre of the densely populated city of Colombo has an algal productivity which is two and a half times as great as that situated in a vast area of uncultivated land. The mountain lake, surrounded by cultivated hills, occupies an intermediate position between the low country lakes in regard to productivity.The environmental factors mainly affecting algal growth, distribution and periodicity in these lakes are temperature, rainfall, sunshine, movement of the water, amount of influx of organic matter and nature of the surrounding soil. In assessing the effect of rainfall consideration has been given not only to the total precipitation, but also to its intensity and the occurrence of periods of drought between those of heavy rainfall.Part of thesis (Ceylonese Plankton Algae) approved for the Degree of Doctor of Philosophy in the University of London and lodged in the Library of that University.  相似文献   

8.
According to the sporo-pollen analysis of the ten localities in Dabusu lake, it could be divided into two sporo-pollen assemblage zones from bottom to top: the lower series (1–2 bed) of Equisetum, lsoites sporo-pollen zone and upper series (3–6 bed) of Ranunculaceae, Chenopodiaceae, Aritemisia sporo-pollen zone. This paper deals also with the course that in the middle later period of the later Holocene Epoch the obvious change of paleogeographic environment is no less than twice in the area surounding Dabusu lake. As for the vegetation, the wet grassy marshland of temperate zone in which the pteridophyta Predominated turned towards meadow -steppe in which herbs predominated. While the wet climate turned towards arid climate and the fresh water lake turned towards salt lake.  相似文献   

9.
大尺度生态景观对麦长管蚜迁入的影响   总被引:1,自引:0,他引:1  
【目的】解析不同生态景观对于麦长管蚜Sitobion avenae(Fabricius)迁飞和降落的影响,为预测预报提供科学指导。【方法】在麦长管蚜迁入期,选取了多个山脉、河流、湖泊等典型的大生态景观,抽样调查其周围麦田中麦长管蚜有翅成蚜的百株蚜量。【结果】调查显示,有翅成蚜量山的南侧比北侧多,而湖泊和河流附近的有翅成蚜量一般少于远处。山脉对麦长管蚜有翅成蚜迁入有明显阻挡作用,高海拔地区有利于有翅成蚜的迁入,孤山也对有翅成蚜迁入降落存在影响,虽然河流和湖泊对有翅成蚜的迁飞不会产生生态阻隔,但河流和湖泊景观附近不利于有翅成蚜的降落。【结论】大尺度生态景观对麦长管蚜的迁入具有明显影响,不同的生态景观类型影响程度存在差异。  相似文献   

10.
关于元谋人化石地质时代的讨论   总被引:15,自引:5,他引:10  
根据对元谋组(广义)的岩石地层,古生物地层和磁性地层的重新认识,确认由广义的元谋组建立上新统沙沟组、下更新统元谋组(狭义)和中更新统上那蚌组的划分。 元谋人化石产出在上那蚌组,时代为中更新世,处在古地磁极性柱的布容正向期的底部,其时代应不超过73万年,即可能为距今50—60万年。  相似文献   

11.
马尾松毛虫灾变发生类型与地貌及植被特征间对应分析   总被引:3,自引:0,他引:3  
1 引  言对应分析 (correspondenceanalysis)由法国Benzecri于1970年首先提出 ,是在R型和Q型因子分析基础上发展起来的一种多元分析方法[5] .它与主成分分析有着密切的联系 ,在某种意义上可以看成是主成分的特殊情形 ,从另外一种意义上讲 ,它又是主成分分析的推广 .另外 ,它和典型分析也是相通的[4 ] .对应分析的主要目的是寻求列联表行因素和列因素的基本分布特征和最优联立表示 ,并将彼此间的结构关系直观地展示出来 .对应分析已被用于生物学研究的不同领域[2 ,3 ] .本文应用对应分析方法 ,对小班 (s…  相似文献   

12.
Apple farming is an important activity and profession of farmer communities in the Himalayan states of India. At present, the traditional apple farming is under stress due to changes in climate. The present study was undertaken in an Indian Himalayan state, Himachal Pradesh, with the major aim of studying perceptions of farmers on the effects of climate change on apple farming along the altitudinal gradient. Through questionnaire survey, the perceptions of farmers were recorded at low hills (<2500 m), mid-hills (2500–3000 m), and upper hills (>3000 m). At all elevation range the majority of farmers reported that there was increase in atmospheric temperature, and hence at low hills 72% farmers believed that this increase in temperature was responsible for decline in fruit size and so that the quality. Thirty five percent farmers at high hills and 30% at mid hills perceived frost as a major cause for damaging apple farming whereas at low hills 24% farmers perceived hailstorm as the major deterrent for apple farming. The majority of farmers, along the altitude (92% at high hills, 79% at mid hills and 83% at low hills), reported decrease in snowfall. The majority of farmers at low altitude and mid altitude reported decline in apple farming whereas 71% farmers at high hill areas refused decline in apple farming. About 73–83% farmers admitted delay in apple’s harvesting period. At mid hills apple scab and at low hills pest attack on apple crops are considered as the indicators of climate change. The change in land use practices was attributed to climate change and in many areas the land under apple farming was replaced for production of coarse grains, seasonal vegetables and other horticulture species. Scientific investigation claiming changes in Indian Himalayan climate corroborates perceptions of farmers, as examined during the present study.  相似文献   

13.
The authors examine the genetic structure of the Sardinian population based on the gene frequencies of the ABO blood group system and the Rh factor. The sample, composed of 13,972 individuals, is subdivided on the basis of altitude zones (mountain, internal hills, coastal hills and plains) and by historical-geographic zones. Also examined are the frequencies of a group of communities of different altitude and historical-geographic zones. The results point to genetic heterogeneity within both altitude and historical-geographic zones as well as within the single communities. A distribution gradient is seen for the IA and I0 alleles of the ABO system, namely: mountains, internal hills, coastal hills, plains.  相似文献   

14.
气候变暖对中国栓皮栎地理分布格局影响的预测   总被引:1,自引:0,他引:1  
李垚  张兴旺  方炎明 《生态学杂志》2014,25(12):3381-3389
利用DIVA-GIS软件对中国栓皮栎的地理分布及气候特征进行研究,并用该软件中的Bioclim和Domain两个模型评估未来潜在分布区对气候变暖的响应.结果表明: 中国栓皮栎分布区可分为横断山脉区、云贵高原区、华北山地区、华东山丘区、辽鲁半岛区、台湾海岛区和秦岭巴山区7个亚区,跨越7个温度带、2个干湿区、17个气候区,包括8种气候类型.秦岭-大巴山-伏牛山为栓皮栎的现代多度中心.适合栓皮栎生长的年平均温度为7.5~19.8 ℃,年降雨量为471~1511 mm.Domain和Bioclim模型的受试者工作特征曲线下的面积(AUC值)分别为0.910、0.779,前者预测的高度适生区为秦岭、大巴山、伏牛山、桐柏山、大别山、云贵高原东部和西部、苏皖南部丘陵和华北部分山地.气候变暖趋势下栓皮栎潜在分布区可能向北回缩,面积减小.  相似文献   

15.
Phytoplankton data from 606 lakes were used to characterize indicator taxa of near-pristine reference conditions in clearwater and humic lowland lakes of Northern and Central Europe. Reference lakes were selected based on low pressure from catchment land-use, low population density and the absence of point sources. Reference lakes had low phytoplankton biomass and taxa richness compared to non-reference lakes. In low alkalinity lakes of Northern Europe, the reference communities had high biomass proportions of chrysophytes and low proportions of cyanobacteria; in the Central European high alkalinity lakes, the biomass was distributed more evenly among algal groups. Indicator species analysis and similarity analysis listed 5–29 taxa indicating reference conditions. Indicator taxa differed especially between the low alkalinity and the high alkalinity lakes, but there were also country-specific differences. Most common indicator taxa for the northern reference lakes were chrysophytes (e.g. Bitrichia, Dinobryon). In the Central European reference lakes, diatoms (e.g. Cyclotella) were more characteristic. Despite the differences, there was a general finding that taxa present in reference lakes were often also present in non-reference lakes, but typically in lower biomass proportions; another characteristic of the reference communities is the absence of many taxa typically found in non-reference lakes.  相似文献   

16.
新生代全球变化与中国古植物区系的演变   总被引:6,自引:0,他引:6  
新生代是地质历史最年轻的一个时代 ,当时全球板块运动和岩浆活动强烈而频繁 ,中生代开始的大陆漂移活动继续进行 ,并于早第三纪末开始喜马拉雅运动 ,古地中海逐渐封闭 ,经过一系列的板块碰撞和洋底扩张 ,晚第三纪时地壳构造的基本轮廓和古地理面貌逐渐接近现代。受地壳运动的控制 ,全球新生代气候波动明显 ,早第三纪总体比较温暖 ,晚第三纪气候发生明显分异 ,气温显著下降 ,第三纪末期开始有冰川活动 ,一直持续到更新世末期 ,期间发生多次冰期和间冰期 ,全新世气候逐渐转暖。受上述全球变化的影响 ,我国新生代植物区系纵向演变和横向分异明显 ,早第三纪植物区系主要是纬向分带 ,从古新世到渐新世 ,我国植物区系主要分为北方区和南方区 ;晚第三纪初 ,由于喜马拉雅运动使青藏高原及东部的横断山脉地区持续抬升 ,逐渐形成独立的高原植物区。总体来说 ,晚第三纪植物区系和植被类型逐渐接近现代。第四纪由于青藏高原继续强烈抬升 ,激发了东亚季风 ,使我国的植物区系经向分带更加明显 ,植物区系和植被类型与现代已基本一致 ,到了全新世晚期 ,植物区系的演变除了受全球变化的影响外 ,人类活动的作用也越来越明显  相似文献   

17.
廖梦娜  金伊丽  李晨瑜  李凯 《生态学报》2020,40(3):1089-1100
青藏高原东南部高寒山区广泛发育冰川湖泊,湖泊沉积过程同时受控于区域气候、流域水文、地质条件及湖泊形态特征。基于放射性210Pb/137Cs和14C定年法,对巴松错沉积物理(粒度、分选系数)和化学指标(TOC、TN、C/N)进行分析,发现18世纪末到19世纪末湖泊沉积过程显著变化,表现为迅速变缓趋势。通过分析区域树轮重建的气候序列(温度、降水及相对湿度)及冰川地貌调查资料,认为气候变化及流域冰川分布位置是影响该湖泊沉积过程的重要因素。小冰期末期冰川前缘靠近湖区,随后温度上升导致冰川融水激增、水动力加强,从而引起湖泊沉积粒度的粗化。随着冰川前缘不断后退,径流输送距离增长、沉积分选变好、粒度细化。此外,该地区活跃的地质活动也可能是湖泊沉积过程明显变化的重要诱因。湖泊沉积硅藻是研究气候环境变化的有力指标。过去200多年巴松错硅藻组合变化不明显(DCCA=0.47 SD),说明该地区气候环境变化未超过其生态阈值。通过与其他沉积指标进行对比分析发现,巴松错硅藻记录受到流域水文和湖泊沉积过程影响,主要表现为外源输入和/或湖岸浅水区来源...  相似文献   

18.
藏北地区生态与环境敏感性评价   总被引:5,自引:0,他引:5  
藏北地区自然条件极为严酷,生态与环境非常脆弱和敏感。采用地理信息系统手段与综合评价方法,对藏北地区主要生态与环境敏感性问题进行评估,分析了土壤侵蚀、沙漠化和草地退化等方面的敏感性空间分异规律,指出了今后生态与环境建设的优先区域。结果表明:藏北地区土壤侵蚀敏感区占土地总面积的42.5%,主要分布于东中部区域;藏北地区沙漠化敏感区面积较大(占土地总面积的78.8%),主要分布在人类活动强度相对较低的西北部;藏北中东部和北部地区草地退化较为严重,尤其是藏北地区冰川与雪山及其周围等气候变化较为敏感区域和交通要道沿线等人类活动较为频繁区域的草地退化相对严重,对草地退化也比较敏感,是今后草地退化治理和恢复的优先区。  相似文献   

19.
1. Changes in cladoceran subfossils in the surface sediments of 54 shallow lakes were studied along a European latitude gradient (36–68°N). Multivariate methods, such as regression trees and ordination, were applied to explore the relationships between cladoceran taxa distribution and contemporary environmental variables, with special focus on the impact of climate. 2. Multivariate regression tree analysis showed distinct differences in cladoceran community structure and lake characteristics along the latitude gradient, identifying three groups: (i) northern lakes characterised by low annual mean temperature, conductivity, nutrient concentrations and fish abundance, (ii) southern, macrophyte rich, warm water lakes with high conductivity and high fish abundance and (iii) Mid‐European lakes at intermediate latitudes with intermediate conductivities, trophic state and temperatures. 3. Large‐sized, pelagic species dominated a group of seven northern lakes with low conductivity, where acid‐tolerant species were also occasionally abundant. Small‐sized, benthic‐associated species dominated a group of five warm water lakes with high conductivity. Cladoceran communities generally showed low species‐specific preferences for habitat and environmental conditions in the Mid‐European group of lakes. Taxon richness was low in the southern‐most, high‐conductivity lakes as well as in the two northern‐most sub‐arctic lakes. 4. The proportion of cladoceran resting eggs relative to body shields was high in the northern lakes, and linearly (negatively) related to both temperature and Chl a, indicating that both cold climate (short growing season) and low food availability induce high ephippia production. 5. Latitude and, implicitly, temperature were strongly correlated with conductivity and nutrient concentrations, highlighting the difficulties of disentangling a direct climate signal from indirect effects of climate, such as changes in fish community structure and human‐related impacts, when a latitude gradient is used as a climate proxy. Future studies should focus on the interrelationships between latitude and gradients in nutrient concentration and conductivity.  相似文献   

20.
藏北高原植被物候时空动态变化的遥感监测研究   总被引:9,自引:0,他引:9       下载免费PDF全文
利用遥感数据提取的植被物候格局及时空变化特征能很好地反映区域尺度上植被对全球变化的响应。目前关于青藏高原地区植被物候的少量报道基本上是基于物候站点的观测记录展开分析的。该文基于非对称高斯拟合算法重建了藏北高原2001-2010年的MODIS EVI (增强型植被指数)时间序列影像, 然后利用动态阈值法提取整个藏北高原2001-2010年植被覆盖的重要物候信息, 包括植被返青期、枯黄期与生长季长度, 分析了植被物候10年间平均状况的空间分异特征以及年际变化情况, 并结合站点观测记录分析了气温和降水对植被物候变化的影响, 结果表明: (1)藏北高原植被返青期在空间上表现出从东南到西北逐渐推迟的水平地带性与东南高山峡谷区的垂直地带性相结合的特征, 近60%区域的植被返青期提前, 特别是高山地区; (2)植被枯黄期的年际变化不太明显, 大部分地区都表现为自然的年际波动; (3)生长季长度的时空变化特征由植被返青期和枯黄期二者决定, 但主要受返青期提前影响, 大部分地区生长季长度延长; (4)研究区内不同气候区划植被物候的年际变化以那曲高山谷地亚寒带半湿润区和青南高原亚寒带半干旱区的植被返青期提前和生长季延长程度最为明显; (5)基于气象台站数据分析气候变化对物候的影响发现, 返青期提前及生长季延长主要受气温升高的影响, 与降水的关系尚不明确。  相似文献   

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