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1.
A study on the distribution of Ephemeroptera, Plecoptera, Trichoptera and Odonata in relation of environmental interruptions was done at three different rivers tributaries of Bukit Merah Reservoir, Perak namely Sungai Jelai, Sungai Ara, and Sungai Kurau from October 2013 to January 2014. A total of 1 942 individuals were collected during the 4month of the study. The number of Ephemeroptera was highest, which was found at Sungai Jelai and Sungai Kurau and dominated by Baetis from family Baetidae while at Sungai Kurau dominated by Trichoptera, Hydropsyche from family Hydropsychidae. Ecological and biological indices have been used to evaluate the diversity of Ephemeroptera, Plecoptera, Trichoptera and Odonata at each river. The highest Simpson's diversity index(D=0.893) and Pielou's evenness index(E=0.803) were recorded at Sungai Jelai while Sungai Ara had the highest value of Margalef's richness index(MgR I=5.698). The variance for the assemblages of Ephemeroptera, Plecoptera, Trichoptera and Odonata influenced by9 chemical and physical variables was really a satisfactory with total variance explained of 57.2%. The results of canonical correspondence analysis(CCA) model showed that two groups of insects taxa characterized by water parameters.The first group from the CCA analysis clustered the Ephemeroptera, Plecoptera, Trichoptera and Odonata genera showed that deterioration in dissolved oxygen concentration, pH and nitrate while the second group showed dependence on total dissolved solids(TDS), conductivity, total suspended solid(TSS) and velocity. The study showed that the distribution of Ephemeroptera, Plecoptera, Trichoptera and Odonata taxa was affected by the environmental interruptions such as human residential area, agricultural plantation and river embankment.  相似文献   

2.
2009年5月(平水期)和9月(丰水期)研究了泰州溱湖国家湿地公园11个采样点水体环境特征和大型底栖无脊椎动物群落结构,共获得4门6纲15目40科74属93个大型底栖无脊椎动物分类单元.研究结果显示,物种总分类单元数与总氮含量极显著正相关(n=21,r=0.597,p=0.004),Shannon-Wiener多样性指...  相似文献   

3.
Fossil Trichoptera (caddisfly) remains have been identified and quantitatively recorded in the late-glacial and early-Holocene sediments from Kråkenes Lake, western Norway. The sediment sequence was deposited between 12,300 and 8850 14C BP, covering the Allerød, Younger Dryas, and early-Holocene periods. The first Trichoptera were recorded at 12,000 14C BP, and during the Allerod a diverse assemblage of Limnephilidae taxa developed in the lake. By about 11,400 14C BP the relatively thermophilous Polycentropus flavomaculatus and Limnephilus rhombicus were present, suggesting that the summer water temperature was at least 17 °C. This temperature fell by 5-8 °C at the start of the Younger Dryas, and the thermophilous taxa were replaced within 20-40 14C yrs by Apatania spp., including the arctic-alpine A. zonella, suggesting a maximum summer water temperature of 10-12 °C. The Trichoptera assemblage was impoverished in numbers and in diversity over the next 200 yrs as the severe conditions of the Younger Dryas developed. As soon as temperatures rose and glacial meltwater and silt input ended about 700 14C yrs later, the resident Apatania assemblage expanded immediately, within 10 yrs. About 130 yrs later, thermophilous taxa replaced Apatania, and a much more diverse assemblage than in the Allerod occupied the varied habitats made available by the development of the Holocene lake ecosystem. The 130 yr delay may have been caused by a gradual temperature increase crossing a critical threshold, or by the time taken for thermophilous taxa to migrate from their Younger Dryas refugia.  相似文献   

4.
This study aims to evaluate the effects of variable water flow on macroinvertebrate composition and taxon richness in a semi-arid intermittent stream. Chironomid larvae were the most abundant group of insects in the intermittent stream studied. Nevertheless, their response to flow was similar to the macroinvertebrate fauna as a whole. Macroinvertebrates were more abundant in the late wet phase and in the drying phase. A higher richness was also observed during this period, when new taxa where registered. Discharge, temperature, conductivity and dissolved oxygen were the main variables explaining the variation in richness and density of macroinvertebrate. These variables were also important in explaining the variation in community composition through time. It is suggested that invertebrates cope with the extreme intermittent flows by resilience during variable flows in the wet phase and by resistance during the dry phase. It is however important to notice that frequently high discharges drive the community to lower richness and densities, whereas the resistance during the dry phase is characterized by a taxonomic shift resultant from the survival of the few taxa that supports the initial desiccation and the opportunism of colonizing predaceous taxa overcoming non-resistant taxa.  相似文献   

5.
Travertine deposits of calcium carbonate can dominate channel geomorphology in streams where travertine deposition creates a distinct morphology characterized by travertine terraces, steep waterfalls, and large pools. Algae and microorganisms can facilitate travertine deposition, but how travertine affects material and energy flow in stream ecosystems is less well understood. Nearly a century of flow diversion for hydropower production has decimated the natural travertine formations in Fossil Creek, Arizona. The dam will be decommissioned in 2005. Returning carbonate-rich spring water to the natural stream channel should promote travertine deposition. How will the recovery of travertine affect the ecology of the creek? To address this question, we compared primary production, decomposition, and the abundance and diversity of invertebrates and fish in travertine and riffle/run reaches of Fossil Creek, Arizona. We found that travertine supports higher primary productivity, faster rates of leaf litter decomposition, and higher species richness of the native invertebrate assemblage. Observations from snorkeling in the stream indicate that fish density is also higher in the travertine reach. We postulate that restoring travertine to Fossil Creek will increase stream productivity, rates of litter processing, and energy flow up the food web. Higher aquatic productivity could fundamentally shift the nature of the stream from a sink to a source of energy for the surrounding terrestrial landscape.  相似文献   

6.
We report here on the first detailed ostracode stratigraphic record to be obtained from late Holocene sediments of Lake Tanganyika. We analyzed four cores, three from the northern lake region and a fourth from a more southern lake locality, that collectively record ostracode assemblages under a variety of disturbance regimes. These cores provide a stratigraphic record of ostracode abundance and diversity, as well as depositional changes over time periods of decades to millennia. We have investigated the fossil ostracodes in these cores by looking at temporal changes of species diversity and population structure for the species present. All four cores provided distinct patterns of ostracode diversity and abundance. BUR-1, a northern lake core obtained close to the Ruisizi River delta, yielded a sparse ostracode record. Karonge #3, another northern core from a site that is closely adjacent to a river delta with high sediment loading, yielded almost no ostracodes. The third core 86-DG-14, taken from a somewhat less disturbed area of the lake, suggests that there have been recent changes in ostracode populations. Through most of the lower portion of this core, ostracode abundance is low and species richness is relatively constant. Above 7 cm there is a marked increase in ostracode abundance and a corresponding decrease in species richness, probably signaling the onset of a major community disturbance, perhaps due to human activities. The southernmost core, 86-DG-32, is from a site that is well removed from influent rivers. Ostracode abundance varies erratically throughout the core, whereas species richness is relatively constant and high throughout the core. The temporal variation evident in ostracode community makeup both within and between the studied cores may be a result of naturally patchy distributions among ostracodes, coupled with local extinctions and recolonizations, or it may reflect inadequate sampling of these high diversity assemblages. In either case, these cores illustrate the potential to obtain high resolution ostracode records from the rich, endemic fauna of Lake Tanganyika that can be used to address questions about the history of community structure and human impacts in this lake.  相似文献   

7.
This paper examines the use of fossil larval trichopteran communities to investigate and describe the flow environment of a paleochannel network in the middle reaches of the River Trent floodplain (UK). Previous research utilising fossil insect communities (principally O. Coleoptera, O. Chironomidae) has focussed upon climate reconstruction. However, larval trichopteran communities (O. Trichoptera) also offer an aquatic signal, giving information regarding channel habitat structure and flow environments. The taxonomic diversity of each fossil community and the categorisation of each taxon into a known flow group, using the “LIFE” methodology, facilitates the reconstruction of the river flow conditions at each site based upon known faunal associations with mean flow velocity. A total of 49 trichopteran taxa were recorded from 17 paleochannels (n = 170 samples). Detrended Correspondence Analysis (DCA) identified a environmental gradient on the first DCA axis that reflected variability in flow, from rapid/fast flow to slow flowing and standing water habitats. In addition, two distinct faunal groups were identified on the second DCA axis characteristic of (i) small nutrient rich lentic habitats; and (ii) larger water bodies displaying features of both lentic, lotic and ephemeral habitats where marginal vegetation is abundant on a mineral substratum. The results demonstrate that larval Trichoptera can be used in paleolimnological research to reconstruct a flow signal and provide additional information regarding the aquatic habitat structure. Their wider use in describing the aquatic environment, in association with other proxies (e.g., Chironomidae and Coleoptera), may provide a more holistic understanding of floodplain paleoenvironment succession.  相似文献   

8.
陈波  何剑锋 《极地研究》1994,6(2):56-64
本文分析了长城湾夏季作为异养微型浮游生物主要类群的领鞭毛类(choanoflagelates)的生态分布和丰度。共记述7个属的11个种。领鞭毛类是长城湾夏季的一个丰富的类群,其总丰度在5.1×103-5.3×104细胞/升范围。但其最大丰度和最大叶绿素a浓度不在表层,而分别在20米和30米水层。在垂直丰度上领鞭毛类显现随叶绿素a浓度而增减的趋势。根据对40组数据的回归分析表明:长城湾夏季领鞭毛类总丰度和叶绿素a浓度之间存在着正相关关系。长城湾夏季领鞭毛类四个优势种Bicostaspinifera,Crinolinaaperta,Diaphanoecamultiannulata和Parvicorbiculacircularis广泛地分布于自表到底的各水层中,占各水层领鞭毛类总丰度的90%以上。B.spinifera是表层最丰富的种类,占表层领鞭毛类总丰度平均值的41%。D.multiannu-lata在1991年1月25日的20米水层达到2.2×104细胞/升的单种最大丰度  相似文献   

9.
This work reports the results of one year's sampling of aquatic macroinver-brates in various streams with different salinity gradients. The study area was the headwaters of the rivers Guadaíra and Guadalete, located in the same geographical area in south-western Spain. The most interesting feature of the Guadaíra basin is the natural salinity of its waters due to the abundance of gypsum in its headwaters. Lithologically, the headwaters of the Guadalete basin flow over marls, clay, sandstone and limestone. Salinity values in most streams do not reach 1 mS cm–1. At least at the levels of salinity found in the Guadaíra basin headwaters, the existence of a well-structured community of macroinvertebrates can be claimed. Of the groups studied, Diptera and Coleoptera showed the highest species richness, being distributed preferentially at the ends of the conductivity spectrum. Groups including taxa inhabiting waters of low salinty and taxa inhabiting waters with high salinity could be reliable indicators of salinity.  相似文献   

10.
基于2012年7月至2013年8月调查的江西铜钹山自然保护区贝类资源,研究保护区内贝类的物种多样性,以及在不同生境类型下的分布规律和区系与动物地理组成,探索该地区内贝类物种组成和栖息环境之间的关系。通过定性与定量的方法共采得贝类42种及亚种,分别隶属于2纲4目16科28属。其中,淡水贝类15种,分别隶属于2纲3目7科10属;陆生贝类27种,分别隶属于1纲3目9科18属,其中有3种为江西的新记录:小柱倍唇螺(Diplommatina paxillus)、三重真卷螺(Euplecta trifilaris)和小石环肋螺(Plectotropis calculus)。淡水贝类优势种为放逸短沟蜷(Semisulcospira libertine)和小土蜗(Galba pervia),陆生贝类优势种为扁恰里螺(Kaliella depressa)、弗氏巴蜗牛(Bradybaena fortunei)和灰尖巴蜗牛(Bradybaena ravida ravida)。贝类动物地理区系组成以东洋界为主,共22种,占总种数的52.38%。采用Margalef丰富度指数dMA、Shannon-Wiener(1949)多样性指数H'、Pielou均匀度指数JSW对在不同生境类型下的贝类多样性进行分析,结果表明:灌丛生境陆生贝类的丰富度指数和多样性指数均最高,针阔混交林生境的均匀度指数最高。根据Jaccard公式计算并比较铜钹山与邻近自然保护区陆生贝类物种相似性系数发现:铜钹山自然保护区陆生贝类物种较丰富;与阳际峰自然保护区陆生贝类物种相似系数较高,为23.33%,与湖南莽山自然保护区物种相似性系数较低,为6.45%,并对其相似性差异进行了原因分析。  相似文献   

11.
Testate amoebae are informative about palaeoecological conditions, but the methods generally used for their analyses in lake sediments differ from those used for their analyses in peats, making comparisons difficult. This study examines how filter mesh size and total number of individuals counted affect species richness, Shannon diversity, equitability, density and assemblage structure. We analysed the complete testate amoeba contents of six sediment samples from Lake Lautrey, France. The abundance of testate amoebae was high (1,403–10,870 shells cm−3), and species smaller than 63 μm in both length and width represented up to 89% of total abundance and 43% of species richness. A simulation showed that using 47- or 63-μm mesh-size filters reduced inter-sample differences and changed the patterns of abundance, species richness and assemblage structure, causing loss of information and leading to potential erroneous palaeoecological interpretation. Rarefaction analyses suggest that although 170 shells are sufficient to assess the general structure of assemblages, such small sample sizes can underestimate species richness by overlooking taxa with relative abundances <4%. Total counts of 400 shells yield better estimates of assemblage structure and recover at least 50% of total species richness, although species with absolute frequencies below 2% may still be missed. Higher counts are required to obtain reliable estimates of species richness and assemblage structure in samples that have high testate amoeba densities but are dominated by a few small taxa. Further studies should determine the bioindicator value and functional roles of small and/or rare species in lakes and thus to what extent overlooking them affects palaeoecological interpretations.  相似文献   

12.
Human impacts to mountain streams   总被引:5,自引:2,他引:5  
Ellen Wohl   《Geomorphology》2006,79(3-4):217
Mountain streams are here defined as channel networks within mountainous regions of the world. This definition encompasses tremendous diversity of physical and biological conditions, as well as history of land use. Human effects on mountain streams may result from activities undertaken within the stream channel that directly alter channel geometry, the dynamics of water and sediment movement, contaminants in the stream, or aquatic and riparian communities. Examples include channelization, construction of grade-control structures or check dams, removal of beavers, and placer mining. Human effects can also result from activities within the watershed that indirectly affect streams by altering the movement of water, sediment, and contaminants into the channel. Deforestation, cropping, grazing, land drainage, and urbanization are among the land uses that indirectly alter stream processes. An overview of the relative intensity of human impacts to mountain streams is provided by a table summarizing human effects on each of the major mountainous regions with respect to five categories: flow regulation, biotic integrity, water pollution, channel alteration, and land use. This table indicates that very few mountains have streams not at least moderately affected by land use. The least affected mountainous regions are those at very high or very low latitudes, although our scientific ignorance of conditions in low-latitude mountains in particular means that streams in these mountains might be more altered than is widely recognized. Four case studies from northern Sweden (arctic region), Colorado Front Range (semiarid temperate region), Swiss Alps (humid temperate region), and Papua New Guinea (humid tropics) are also used to explore in detail the history and effects on rivers of human activities in mountainous regions. The overview and case studies indicate that mountain streams must be managed with particular attention to upstream/downstream connections, hillslope/channel connections, process domains, physical and ecological roles of disturbance, and stream resilience.  相似文献   

13.
This study was conducted in the arid Mediterranean Reserve located in northern Jordan, representing a continuous grazed arid rangeland ecosystem. Quantitative analyses on species diversity in addition to phytogeographical analysis were conducted. Some ecological parameters such as, life forms, growth forms, species density and frequency were investigated. A total of 93 vascular plant taxa belonging to 78 genera and 26 families were reported. This constitutes about 4.3% of the total flora of Jordan. Reported taxa include 13 species of grasses, 69 forbs and 10 shrubs and semi-shrubs. The botanical survey pointed to the presence of four rare species in Jordan. Plant species were classified into 28 functional groups. Pairwise correlation analyses among the most abundant species, showed that neutral associations dominated (75%) those communities, followed by positive associations (19%), while only (6%) showed negative association. Positive association may be attributed to direct facultative mutualism, or to physical environmental heterogeneity. Such a positive cooperation in the plant community can significantly maintain species diversity in adverse environments.The relationship between primary productivity and species richness showed a humpbacked pattern. Maximum richness corresponded to a biomass level of 300–400 g m−2. However, a sinusoidal curve-fitting model explained the relationship between graminoids biomass and species richness. These findings pointed to the adaptation of plant taxa to livestock grazing and to the small-scale spatial and environmental heterogeneity in arid Middle Eastern Mediterranean rangelands. Results suggest that optimal biodiversity conservation for the arid Middle Eastern grazing lands should consider their high level of spatial heterogeneity. Rangeland managers should adopt grazing plans that apply a range of grazing pressure across the area so as to maintain diversity at local and regional scales.  相似文献   

14.
As saline streams are geographically widespread in arid and semiarid regions, flow intermittence frequently occurs as another stressor factor apart from salinity. Rambla Salada is a temporary naturally saline stream with an intermittent reach upstream. This stream is an ideal scenario to study the effects of intermittent stream flow on macroinvertebrate community composition and biological traits in a naturally saline Mediterranean stream. This study analysed three sites with different hydrological regimes (one intermittent and two perennials). Flow intermittence exerted low pressure on the macroinvertebrate composition and biological traits which led to the loss of drought-intolerant species and taxa rather than acting as a selective force to promote desiccation-resistant taxa. Macroinvertebrate community at the intermittent site was a subset of the community found in perennial sites, and the presence of flier taxa at this site helped avoid flow cessation. These minor changes have consequences to assess the ecological quality of these saline temporary streams in the context of the Water Framework Directive, given the major differences revealed by some indices between the intermittent and perennial sites as the former obtained lower values due to the presence of few desiccation-intolerant species, which significantly increased the value of those biological indices.  相似文献   

15.
Patterns of plant diversity were examined across 24 ironstone ranges in arid south western Australia. The high levels of beta diversity displayed between ranges primarily resulted from high turnover of perennial species and was not influenced by the lower species richness on the more arid ranges. The variance in composition of the vegetation across the ranges was evenly distributed between the broad spatial pattern and environmental factors measuring climate gradients, local site variables and soil chemistry. In contrast broad scale spatial and climatic gradients were most important in explaining the variance in perennial species richness. Ranges along the boundary of the Arid Zone appear to have acted as refugia during the climatic cycles of the Tertiary with several hotspots of species endemism and taxa with distributions centered on these ranges. On the more arid ranges these specialist ironstone taxa are largely absent. The variation in richness of these specialists taxa was strongly influenced by patterns in soil chemistry in addition to the broad scale spatial and climate gradients. The concentration of the ironstone specialist taxa is largely coincidental with the most prospective areas for iron ore mining and this will provide considerable challenges in conserving these unique ecosystems.  相似文献   

16.
Chironomid analysis was performed on late-glacial sediment from four New Brunswick lakes in order to gain basic ecological information regarding the richness and diversity of late-glacial chironomid assemblages, and to compare the pattern of succession at each site. At all sites, the richness and diversity of the larval assemblages were lowest immediately following deglaciation and during the Younger Dryas, corresponding to the coldest times of the late-glacial period. Although cold-stenothermous taxa are characteristic of sediments deposited immediately following deglaciation, as well as during the Killarney Oscillation and Younger Dryas cooling events, the constituent taxa are different at each site. During the intervening warm periods, the larval assemblages at each site are also dissimilar, with the more southern sites containing a greater variety of temperate littoral taxa. This raises the possibility that a north-south temperature gradient existed during the warm intervals of the late-glacial period in New Brunswick.  相似文献   

17.
The position of mountain streams high in the channel network and their proportional dominance mean that channel modifications and adjustments within these systems will have important implications for downstream processes and linkages. This study develops an analysis framework for examining the catchment-scale distribution of reach morphologies, and the relationship among reach type, catchment lithology and flow competence in southeast Australian mountain streams. The analysis framework is applied to three catchments which have contrasting proportions of the two dominant lithologies of the region, Devonian granites and Ordovician metasediments.The model successfully delineated 68% of reach types, and the resultant spatial maps allowed the effects of stream network position and catchment specific controls on channel morphology to be evaluated. Maximum lengths of the majority of reach morphology types were in second-order streams and the maximum number of morphology types (six) was present in third-order streams, with dramatic reductions in reach type variability as the network expands. The position of catchment lithology within the channel network structure was recognized as more important than the aerial extent of a particular lithology on the distribution and abundance of reach morphologies. The model provides an important tool in the management of channel networks for the protection or restoration of ecological diversity, by identifying river segments and tributaries with high morphological diversity.  相似文献   

18.
干旱荒漠螨类和跳虫对降雨的响应   总被引:1,自引:1,他引:0  
目前关于降水变化如何影响和调控荒漠土壤动物分布及多样性的形成与维持生态学机制的认识非常有限。通过对自然降雨后红砂和泡泡刺灌丛下螨类和跳虫群落的动态监测,揭示荒漠小型节肢动物群落组成及多样性对降雨变化的响应规律。结果表明:干季降雨对两种灌木下小型节肢动物、螨类和跳虫数量及类群丰富度影响较小,而湿季降雨对两种灌木下螨类和跳虫数量及类群丰富度影响较大。如7月24.8 mm和8月6.8 mm降雨后两种灌木下小型节肢动物群落、螨类和跳虫的数量及类群丰富度均显著高于5月4.0 mm、6月14.8 mm和6.6 mm的降雨。6月14.8 mm和6.6 mm降雨后两种灌木下小型节肢动物群落在第2天和3天出现峰值;而7月24.8 mm降雨后两种灌木下小型节肢动物群落均呈现先降低后增加的模式;8月6.8 mm降雨后红砂灌丛下小型节肢动物群落呈降低的趋势,而泡泡刺灌丛下小型节肢动物群落变化较小。泡泡刺灌丛下螨类数量及类群丰富度均高于红砂灌丛,而两种灌木下跳虫数量及类群丰富度相差较小,这可能会影响湿季荒漠小型节肢动物群落对自然降雨变化的响应模式。  相似文献   

19.
中国植物地理学从20世纪20年代初创到当前繁荣经历了100年的发展,近30年来测序技术和生物信息技术的进步,促进了分类、进化和生态等学科交叉融合,中国植物地理学在诸多方面取得了突破性进展,主要包括:① 植物类群和区系在中国整体上按纬度、经度和海拔呈现出规律性;物种丰富度、系统发生多样性和特有性热点集中分布在南部山地,少数分布在北方山地和干旱地区。② 关于大尺度植物多样性格局及形成机制,多数热带起源科的物种多样性格局受冬季低温的限制,而多数温带起源科的物种多样性格局由末次冰期以来的气候变化主导;中国山地植物和群落具有显著的垂直地带性和空间分布异质性,热量因子是中国高山植物区系地理分异的首要气候因子。③ 中国大多数现生被子植物属(约66%)是在中新世及其以后分化;500 mm年等降水线是中国植物区系年龄和植被分区最重要的分界线;中国植物区系、区系中的特征或关键类群的起源和多样化与青藏高原抬升和亚洲季风加强密切相关。未来,时间和空间的结合仍是植物地理学研究的主旋律,类群、群落和区系分化时间的估算及物种分布数据的分辨率是研究者关注的焦点,植物大数据的持续积累和完善将为学科发展提供强大动力和广阔前景。  相似文献   

20.
珠海市重要湿地鱼类多样性   总被引:1,自引:1,他引:0  
2015年10月,调查了珠海湿地水域的鱼类资源。共采集鱼类样品261尾,隶属于7目16科22属23种,其中鲱形目2科3属4种;鲤形目2科6属6种;鲶形目1科1属1种;鲻形目1科1属1种;合鳃鱼目1科1属1种;鲈形目8科9属9种;鲽形目1科1属1种。Margalef物种丰富度指数为1.022~2.635;Simpson指数为0.365~0.765;Shannon-wiener多样性指数为0.722~1.961;Pielou均匀度指数为0.448~0.765。珠海湿地水域的鱼类群落多样性较低,各样点间的鱼类组成差异明显。  相似文献   

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