Main Community Types Research Articles

Quantitative classification and biodiversity characteristics of plant communities in Luoshan Mountain steppe, Ningxia, China

To understand the distribution pattern and influencing factors of plant community and diversity along the altitude gradient, we examined plant community types, plant diversity and phylogenetic diversity of mountain steppe in Luoshan, Ningxia, and analyzed the relationship between the plant community and its diversity and environmental driving factors. The results showed that the main community types in the mountain steppe were Asterothamnus centraliasiaticus community, Caragana tibetica community, Convolvulus tragacanthoides community, Stipa bungeana community, Stipa breviflora＋Ajania achilloides community, Artemisia frigida community, Roegneria alashanica＋S. breviflora＋Hedysarum polybotrys community, S. breviflora＋Stipa grandis community, S. grandis＋S. bungeana community, Cyperus glomeratus community, S. grandis community and Carex aridula community. The distribution of mountain steppe community was mainly affected by altitude, soil alkali-hydrolyzed nitrogen, water content, available potassium, silt and organic matter contents, with altitude and soil water content having the greatest effects (P<0.01). The Patrick index and phylogenetic diversity index (PD) of plant community showed an increasing trend with the altitude increase, the Shannon index and Pielou index showed a unimodal trend, and the phylogene-tic structure gradually changed from aggregation to dispersion. There was a significant positive correlation between species diversity index and PD index. Shannon index was negatively correlated with net relatedness index (NRI). Plant species diversity and phylogenetic diversity of mountain steppe were mainly affected by soil water content, available potassium, total nitrogen, silt and sand contents. NTI was significantly affected by altitude, while the NRI index was significantly affected by soil silt content.

Restoration of aquatic macrophytes with the seed bank is difficult in lakes with reservoir-like water-level fluctuations: A case study of Chaohu Lake in China

Aquatic vegetation in lakes along the middle and lower reaches of the Yangtze River has been seriously degraded by human disturbances such as river–lake disconnection and water eutrophication. Chaohu Lake is a typical lake with reservoir-like water-level fluctuations (WLFs). Since a sluice was built in 1962, the coverage of aquatic vegetation in Chaohu Lake has been very low (0.77%). In this study, field investigations of the aquatic vegetation and seed bank of Chaohu Lake were conducted, and aboveground vegetation diversity was found to be low. Forty-eight species were recorded, of which submerged, floating-leaved, and emergent macrophytes were 1, 5, and 10, respectively. Currently, artificially planted Phragmites australis and Salix communities have become the main community types. A total of 18 aquatic macrophytes were identified in the seed bank, of which the number of submerged, floating-leaved, and emergent macrophytes and hygrophytes were 2, 2, 3, and 11, respectively; the seed density was 2.05, 2.05, 16.93, and 9.30 ind./m2, respectively. The seed density of aquatic macrophytes was much lower in Chaohu Lake than in the lakes with quasi-natural WLFs, and the seeds were mainly distributed in the estuary area. Only two emergent macrophyte species (Typha) germinated in the open water area. Spearman correlation analysis showed that the distance to bank was the main environmental factor that affected aquatic macrophyte diversity and seed density in the seed bank. It is not feasible to promote the natural reconstruction and restoration of aquatic macrophytes in Chaohu Lake by decreasing the water level or increasing water transparency, but the area near the estuary can be identified as a priority restoration area (PRA) for aquatic macrophytes. Artificial transformation of the micro-topography can be used to guide some hydrochorous seeds in the tributaries to the PRA and restore aquatic vegetation in the local area.

Species richness and influencing factors of aquatic plant in the Kaidu River Basin, Xinjiang, China

River is a continuous, flowing, unique, and complete ecosystem. Studies on the aquatic macrophyte richness and its influencing factors were important for river ecology study. In this study, species richness, main aquatic plant community types and their quantitative characteristics, and the influencing factors of aquatic macrophyte in the Kaidu River Basin, Xinjiang, were examined by field investigation. We followed the water-energy hypothesis and habitat heterogeneity hypothesis to explain the geographical pattern of species diversity in the basin. The results showed that there were 71 species of aquatic plants belonging to 24 families and 39 genera in the Kaidu River Basin. The aquatic macrophyte communities could be divided into 10 main community types by cluster analysis, among which Phragmites australis association had the highest species richness, and Typha angustifolia association and Ceratophyllum demersum association had the lowest species richness. Shannon index of the aquatic macrophyte community of Kaidu River Basin was significantly negatively correlated with water pH. Simpson index was significantly negatively correlated with pH and longitude, and significantly positively correlated with altitude. The aquatic plant community types in the basin were mainly affected by altitude, water depth, and water temperature. The species diversity changed little in altitude and longtitude. The water-energy dynamic hypothesis and habitat heterogeneity hypothesis together explained 31.4% of the richness patterns of macrophytes, indicating low exploratory power.

河西走廊水生植物多样性格局、群落特征及影响因素

PDF HTML阅读 XML下载 导出引用 引用提醒 河西走廊水生植物多样性格局、群落特征及影响因素 DOI: 10.5846/stxb201810242298 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 湖北省教育厅项目（T201701）；科学技术部资助项目（2013FY112300）；国家自然科学基金面上项目（31570366） Biogeographic pattern, main community types, and the influencing factors of aquatic macrophytes in the Hexi Corridor of Northwest China Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:水生植物是湿地生态系统重要组成部分，研究水生植物多样性分布格局及其影响因素对地区水生植物资源保护具有重要意义。通过野外调查并结合气候等环境因素，研究了河西走廊主要水生植物群落类型、数量特征、水生植物多样性分布格局及影响因素，并对中域效应假说进行了验证。研究结果表明：（1）河西走廊地区共有水生植物29科42属84种，群落的聚类分析可将河西走廊水生植物群落划分为15个主要群落类型；（2）河西走廊水生植物群落类型主要受到水温、海拔、经纬度等环境因子影响，群落物种多样性指数与盐度以及溶解性固体总量呈显著性相关；（3）河西走廊水生植物多样性空间格局呈现出"∩"型的单峰格局，中域效应模型能较好地解释该地区水生植物多样性水平的纬度格局及海拔垂直分布格局，对该区域水生植物物种丰富度在纬度和海拔梯度上的变异解释率分别为57.56%、63.5%。分析表明，河西走廊水生植物物种丰富度格局由几何（边界）限制和随机过程及其他未知因素共同控制，且几何（边界）限制和随机过程贡献率较大；同时本研究中未考虑的环境异质性、气候、人为干扰等因素也对河西走廊水生植物多样性空间分布产生重要影响。 Abstract:Aquatic plants are an important part of wetland ecosystems. Studies about the distribution pattern of aquatic plants and its influencing factors can provide important background for the regional protection of aquatic plant resources. In this study, the main aquatic plant community types, quantitative characteristics, species richness patterns, and influencing factors of aquatic plants in the Hexi Corridor were studied using field investigation data. The mid-domain effect hypothesis was used to explain geographical diversity patterns of aquatic macrophytes in the region. The main results are as follows:(1) there were 84 species belonging to 42 genera of 29 families of aquatic plants in the Hexi Corridor. Cluster analysis of the community showed that there were 15 main aquatic plant community types in this region; (2) the aquatic plant community types in the Hexi Corridor were mainly affected by environmental factors such as water temperature, elevation, latitude, and longitude. The community species diversity index was significantly correlated with salinity and total dissolved solids; (3) the spatial pattern of aquatic plant diversity in the Hexi Corridor exhibited a unimodal pattern. The mid-domain effect model better explained the latitudinal pattern and the vertical distribution pattern of aquatic plant diversity in the region, with explanation rates reaching 57.56% and 63.5%, respectively. These results indicate that the patterns of aquatic macrophyte species richness in the Hexi Corridor were determined by geometric (boundary) constraints, random processes, and other unknown processes. Geometric (boundary) constraints and random process showed a higher contribution rate on geographic richness gradients. Also, we highlight that unmeasured factors including environmental heterogeneity, climate, and human disturbance may greatly affect aquatic plant species richness in the Hexi Corridor of Northwest China. 参考文献 相似文献 引证文献

天山林区不同群落土壤水分入渗特性的对比分析与模拟

PDF HTML阅读 XML下载 导出引用 引用提醒 天山林区不同群落土壤水分入渗特性的对比分析与模拟 DOI: 10.5846/stxb201810072160 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（U1503187）；"十二五"农村领域国家科技计划课题（2015BAD07B03-03） Comparative analysis and simulation of soil moisture infiltration characteristics in different communities in the forests of Tianshan Mountains, China Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:土壤入渗特性是影响森林生态水文过程的一个重要环节。为了比较不同群落类型土壤水分入渗特性的差异，在天山中段北坡林区利用环刀法测定天然林、人工林、林窗草地、草地、林缘灌木林、山前灌木林六种群落类型的森林土壤入渗过程，对比分析有机质含量、毛管孔隙度、容重、含水率等土壤理化性质对入渗过程的影响，用三种常用模型进行入渗过程模拟，分析比较这些模型在天山林区的适宜性。结果表明：（1）六种主要群落类型前60 min土壤初始入渗率介于2.63-9.00 mm/min之间，稳定入渗率介于0.85-5.12 mm/min之间，不同群落类型土壤平均入渗率从大到小的排序为：天然林 > 林缘灌木 > 林窗草地 > 草地 > 人工林 > 山前灌木；（2）六种群落类型土壤入渗性能均具有初渗速率 > 平均入渗速率 > 稳定入渗速率的相同趋势；（3）Kostiakov模型对试验六种群落类型土壤入渗过程的拟合精度比较高，适用于描述本研究区域水源涵养林地土壤入渗特征；（4）土壤有机质含量与土壤入渗速率呈正相关，且与初始入渗率达到显著水平；土壤的含水率、土壤毛管孔隙度和土壤容重与土壤入渗能力呈现显著的负相关。通过观测与模拟不同群落类型的土壤水分运动过程，本文可为天山林区生态水文长期定位观测提供有益借鉴。 Abstract:Soil infiltration characteristic is an important link that affects forest ecological hydrological processes. To compare differences in soil-water infiltration characteristics of different community types, the double cutting ring method was used to analyse natural forests, Artificial forest, gap grasslands, grasslands, forest edge shrubs, and piedmont shrubs on the northern slope of the Tianshan Mountains. The effects of soil physical and chemical properties, such as organic matter content, capillary porosity, bulk density, and water content, on the infiltration process were compared and analysed. Thress common models were used to simulate the infiltration process, and the suitability of these models in the area was analysed and compared. The results were as follows:(1) The initial infiltration rate of the soil in the first 60 min in the six main community types was 2.63-9.00 mm/min, and the stable infiltration rate was 0.85-5.12 mm/min. The average soil infiltration rate of the different community types ranged from high to low as follows:natural forest > forest edge shrub > gap grassland > grassland > artificial forest > piedmont shrub. (2) The soil infiltration performance of the six community types showed the same trend:initial infiltration rate > average infiltration rate > stable infiltration rate. (3) The Kostiakov model had a high fitting precision for the soil infiltration process of the six community types and was suitable for describing the soil infiltration characteristics of the water conservation forests in this study area. (4) The soil organic matter content was positively correlated with the soil infiltration rate and reached a significant level with initial infiltration rate; the soil-water content, soil capillary porosity, and soil bulk density were significantly negatively correlated with soil infiltration capacity. Observation and simulation of the soil-water movement process of different community types can provide a useful reference for the long-term observation of ecological hydrology in the forest areas of Tianshan. 参考文献 相似文献 引证文献

Plant communities and environmental factors in the Guayana Highlands: monitoring for conservation under future climate change

The Guayana Highlands (GH) constitute a highly diverse, but relatively poorly studied Neotropical biome, comprised of ∼50 flat-topped mountain summits (called tepuis). Previous studies based on warming forecasts for the region suggested that an upward displacement of environmental conditions of 500–700 m could occur by 2100, potentially resulting in the extinction of c. 50% of its endemic flora due to total habitat loss. To assess the ecological responses of the species to climate change, and select the appropriate conservation measures, long-term monitoring of the GH plant communities will be necessary. In this study, the baseline state for future comparisons was established for the best explored tepui in terms of its flora, Roraima-tepui (2810 m), through a floristic characterization of its different vegetation types. We also identified the environmental gradients underlying the major plant communities, and assessed the effects of human activities on the chemistry of soils and water at three field camps. Our results yielded five main community types: three meadows, one shrubland, and one forest, with their corresponding diagnostic species. The herbaceous communities were mainly influenced by the presence of flat sandy soils, with varying flooding capacity. Shrublands and forests were characterized by irregular organic soils with very low pH. Finally, pH values below 3 were measured on an organic soil of a field camp, although further studies will be necessary to attribute this deviation to human activities.

Microbial biofilms associated with intravascular catheter-related bloodstream infections in adult intensive care patients.

Catheter-related bloodstream infection (CRBSI) is one of the most serious complications in hospitalised patients, leading to increased hospitalisation, intensive care admissions, extensive antibiotic treatment and mortality. A greater understanding of these bacterial infections is needed to improve the prevention and the management of CRBSIs. We describe here the systematic culture-independent evaluation of intravascular catheter (IVC) bacteriology. Twelve IVCs (6 central venous catheters and 6 arterial catheters) were collected from 6 patients. By using traditional culture methods, 3 patients were diagnosed with catheter colonisation including 1 patient who also had CRBSI, and 3 had no colonisation. From a total of 839,539 high-quality sequence reads from high-throughput sequencing, 8 microbial phyla and 76 diverse microbial genera were detected. All IVCs examined in this study were colonised with complex microbial communities including "non-colonised IVCs," as defined using traditional culture methods. Two main community types were observed: Enterobacteriaceae spp., dominant in patients without colonisation or CRBSI; and Staphylococcus spp., dominant in patients with colonisation and CRBSI. More diverse pathogens and a higher microbial diversity were present in patients with IVC colonisation and CRBSI. Community composition did not appear to be affected by patients' antibiotic treatment or IVC type. Characterisation of these communities is the first step in elucidating roles of these pathogens in disease progression, and to ultimately facilitate the improved prevention, refined diagnosis and management of CRBSI.

The Relationships among Community Type, Peat Layer Thickness, Belowground Carbon Storage and Habitat Age of Mangrove Forests in Pohnpei Island, Micronesia

This paper quantifies the relationships among community type, peat layer thickness and habitat age of the mangrove forests in Pohnpei Island, Micronesia and provides a discussion concerning the primary succession and the belowground carbon storage of the main mangrove community types. The ages of the habitat were estimated from a relationship between the thickness of the mangrove peat layer and the formative period, which was decided by calibrated radiocarbon ages. Mangrove communities in the coral reef type habitat were generally arranged in the following order, from seaward to landward: 1) the Rhizophora stylosa or Sonneratia alba community (I or II communities), 2) the typical subunit of the S. alba subcommunity of the Rhizophora apiculata— Bruguiera gymnorrhiza community (III(2)a subunit) and 3) the Xylocarpus granatum subunit of the same subcommunity of the same community (III(2)b subunit). Their habitat ages were estimated to be younger than 460 years, between 360 and 1070 years and between 860 and 2300 years, respectively. Based on these results and other evidences such as photosynthetic characteristics and pollen analysis derived from the previous studies, the primary succession was inferred to have progressed in the order mentioned above. Belowground stored carbon for the main community types in the coral reef type habitat were estimated to be less than 370 t C ha-1 for the I and the II communities, between 290 and 860 t C ha-1 for the III(2)a subunit and between 700 and 1850 t C ha-1 for the III(2)b subunit.

Timberline meadows along a 1000-km transect in NW North America: species diversity and community patterns

Question The mountains of NW North America are home to natural meadows that cover large areas at the timberline. The vegetation of these meadows has been the topic of few local studies, and little is known of species composition turnover across mountain ranges and along the latitudinal gradient. We sampled and analyzed community composition along a 1000-km gradient to answer the following questions: (1) what are the main community types in timberline meadows; (2) what are the most important abiotic gradients underlying their composition; and (3) how is species diversity related to environmental factors and how does it change along the latitudinal gradient? Location SE and central British Columbia (Canada), NW Montana (USA). Methods We recorded data on cover and presence/absence of vascular plant, bryophyte and lichen species, as well as structure and environmental properties in 4 m × 4 m plots (n = 112). Using the OptimClass approach, we classified plots into distinct community types. We used NMDS and multiple regressions to analyse the relationship between composition, species richness and environmental and geographic gradients. Results Despite drawing from a large geographic area, our classification revealed only four meadow communities. Mesic meadows were the most frequent and had a pronounced species turnover along latitude, resulting in two distinct community types. In addition, a three-dimensional ordination showed that vegetation structural properties, macroclimate and geographic predictors were important underlying gradients for species composition. Vascular species richness increased with soil pH, and exhibited a quadratic relationship with litter cover and latitude. Furthermore, in the latter case, it increased towards the southern and northern ends of our gradient. Conclusions Detection of only four meadow communities along the 1000-km sampling gradient suggests a relatively recently established flora and a lack of regional differentiation consistent with the low level of endemism in the region. Higher vascular species diversity at the northern and southern edges of our gradient may reflect the geographic proximity to areas unglaciated during the Pleistocene, and suggests that areas farthest from the unglaciated edge may be experiencing colonization debt.

On characters of plant community of rock vegetation of Danxia landform in Xinchang of Zhejiang

Take Changyanshijiufeng and Qianzhangyougu in Xinchang, Zhejiang as examples ,this paper made a survey on the rock vegetation in Danxia landform. The results showed that 30 families, 39 genus and 48 species vascular plants were found there. The main community types were Form. Neyraudia montana, Form. Orostachys erubescens+Sedum polytrichoides , form. Ficus pumila and so on. The composition of flora was complex, and the north temperate and pantropic floristic elements occupied a certain proportion with especially obvious transitional character. The order of species richness and diversity index were: herb layershrub layermoss layer, and the evenness index was: shrub layer moss layerherb layer.

Land degradation and vegetation distribution in Chott El Beida wetland, Algeria

The aim of this study is to explore the environmental factors that determine plant community distribution in northeast Algeria. This paper provides a quantitative analysis of the vegetation–environment relationships for a study site in the Chott El Beida wetland, a RAMSAR site in Setif, Algeria. Sixty vegetation plots were sampled and analysed using TWINSPAN and Detrended Correspondence Analysis (DCA) in order to identify the principal vegetation communities and determine the environmental gradients associated with these. 127 species belonging to 41 families and 114 genera were recorded. Six of the recorded species were endemic representing 4.7% of the total species. The richest families were Compositae, Gramineae, Cruciferae and Chenopodiaceae. Therophytes and hemicryptophytes were the most frequent life forms. The Mediterranean floristic element is dominant and is represented by 39 species. The samples were classified into four main community types. The principal DCA axes represent gradients of soil salinity, moisture and anthropogenic pressure. The use of classification in combination with ordination techniques resulted in a good discrimination between plant communities and a greater understanding of controlling environmental factors. The methodology adopted can be employed for improving baseline information on plant community ecology and distribution in often critically endangered Mediterranean wetland areas.

Environmental factors and vegetation composition, Lefka Ori massif, Crete, S. Aegean

ABSTRACTAim The aim of this study was to explore the environmental factors that determine the spatial distribution of oro‐mediterranean and alti‐mediterranean plant communities in Crete.Location The paper provides a quantitative analysis of vegetation–environment relationships for two study areas within the Lefka Ori massif Crete, a proposed Natura 2000 site.Methods Eleven environmental variables were recorded: altitude, slope, aspect, percentage of bare rock, percentage of unvegetated ground, soil depth, pH, organic matter content and percentages of sand, silt and clay content. Classification of the vegetation was based on twinspan, while detrended correspondence analysis (DCA) and canonical correspondence analysis (CCA) were used to identify environmental gradients linked to community distribution.Results One hundred and twenty‐five species were recorded from 120 plots located within the two study areas. Forty‐seven of the recorded species are endemic, belonging to 35 families. Hemicryptophytes and chamaephytes were the most frequent, suggesting a typical oro‐mediterranean life form spectrum. The samples were classified into five main community types and one transitional. The main gradients, identified by CCA, were altitude and surface cover type in the North‐west site, while in the Central site the gradients were soil formation‐development and surface cover type.Main conclusions The use of classification in combination with ordination techniques resulted in a good discrimination between plant communities and a greater understanding of controlling environmental factors. The methodology adopted can be employed for improving baseline information on plant community ecology and distribution in Mediterranean mountain zones.

Testing the predictivity of ecological indicator values. A comparison of real and `virtual' relevés of lichen vegetation

A complex database on the lichens of Italy was used to combine ecological indicator values assigned to each species (pH, eutrophication, light and aridity), in such a way as to simulate `virtual habitats' from a beech forest of northern Italy. For each habitat, a list of species was obtained (`virtual releve'). A matrix of real and virtual releves was submitted to classification and ordination, obtaining six main community-types, all of which include both real and virtual releves. Two ordinations of species were carried out, one on the matrix of real releves, the other on that of virtual releves: their comparison shows that the consistency and the resolving power of the indicator values was high, but it also permits to detect and correct some errors. The results indicate a high predictivity of the indicator values for constructing ecological scenarios.

Density, biomass and community structure of demersal fishes off the Pacific coast of northeastern Japan

Demersal fish communities were studied on the lower continental shelf and the upper continental slope along the Pacific coast of northeastern Japan. Species composition, number and weight of each species were examined based on otter trawl samples at 45 stations. Mean density and biomass of demersal fishes were 131 ha ‐1 and 21 kg ha ‐1 , respectively. The ten most abundant species comprised of about 95% of total number and weight of overall catch indicating simple species composition. Gadiform fishes Theragra chalcogramma, Gadus macrocephalus and Physiculus maximowiczi were the most important species by number, weight and frequency of occurrences, and three main community types represented by the three key species were recognized. Theragra-dominant community showed higher density and biomass, and lower diversity than Physiculus-dominant community did. Species diversity of demersal fish community was negatively correlated to density and biomass. Density and biomass of demersal fish community were high on the uppermost slope, and the high abundance resulted from low-diversity communities dominated by T. chalcogramma and G. macrocephalus.

An integrated approach to hydropower impact assessment

The submerged aquatic vegetation of 17 Norwegian lakes is described and related to the environmental impacts that result from hydro-electric power (HEP) use of these lakes. Largely based upon physiognomical features, three main community types are discerned. These are denoted as (a) shallow-water, (b) mid-depth, and (c) deep-water community, respectively. The aquatic macrophytes are classified into a plant strategy framework. This classification suggests that these macrophytes frequently exhibit combined traits of the ‘S’ (stress-tolerating), ‘R’ (ruderal), and ‘C’ (competitive) strategies. A plant-strategy index for the lakes is derived from the species classification and related to their HEP use.

Vegetation and soils of North Island, Foveaux Strait, New Zealand

Abstract The vegetation and soils of North Island, in the north-east group of muttonbird islands in Foveaux Strait, are described. The flora consists of 10 ferns, 6 monocotyledons, 35 dicotyledons, and 8 adventives (59 species). The main community types are coastal ledge and rock communities, cliff communities of herbaceous plants, coastal shrubland of Hebe elliptica, Olearia angustifolia, and Senecio reinoldii encircling the island and giving way to Myrsine chaihamica low forest on the plateau and with Myrsine australis low forest in the centre of the island. Scattered over the island are patches of Muehlenbeckia australis and Histiopteris incisa The island is capped with a loess deposit some metres deep which appears to have been largely derived from Foveaux Strait during episodes of low sea level during the Pleistocene. The soils contain many seal gastroliths and have also been strongly influenced by the large colonies of petrels. Chemical analysis of one soil profile under Myrsine australis low forest...