Canonical Correspondence Analysis Ordination Research Articles

Agricultural-Derived organochlorine pesticide residues impact on macroinvertebrate community in an Afrotropical Stream

This study evaluated the impact of pesticide application through agricultural activities in Chanchaga River, Nigeria, using macroinvertebrate data sets obtained for six months (September 2021–February 2022). Four (4) stations, characterized by various agricultural activities, were sampled along the river. Analysis of the water samples for organochlorine pesticide residues (OCP) using Gas Chromatography-Mass Spectrometry (GC/MS) at the peak of the two seasons revealed a high concentration of eleven isomers of organochlorine, which ranged from 0.01 to 0.81 μg/L, and a mean concentration that was above international drinking water standards set by the World Health Organization, the Federal Environmental Protection Agency, and the European Union. The mean concentration of detected OCP was recorded as DDT (0.72 μg/L), Dieldrin (0.59 μg/L), Paraquat (0.54 μg/L), Aldrin (0.49 μg/L), Metribuzin (0.48 μg/L), Butachlor (0.47 μg/L), Alachlor (0.28 μg/L), Atrazine (0.23 μg/L), Phenol (0.10 μg/L), Endrin (0.09 μg/L), and Benzene (0.08 μg/L). Atrazine, alachlor, metribuzin, aldrin, phenol, and endrin showed significant differences across the two seasons (p < 0.05), while dieldrin, butachlor, paraquat, benzene, and DDT showed no significant differences across the two seasons (p > 0.05). A total of 622 macroinvertebrate individuals from 19 species in 18 families from 8 orders were collected. More individuals were collected during the dry season (58.17 %) and the wet season (41.83 %). Canonical Correspondence Analysis (CCA) ordination revealed a strong relationship between species abundance and some organochlorine pesticide residues such as DDT, endrin, metribuzin, atrazine, benzene, and dieldrin. The response of macroinvertebrates to OCP indicates that Chanchaga River is a disturbed river, and the indicator organisms (Lestes sp., Coenagrion sp., Zyxomma sp., Appasus sp., Chironomus sp., Lymnaea natalensis, and Caridina nililotica) can also be used for further biomonitoring.

Biological effects of perfluoroalkyl substances on running water ecosystems: A case study in Beiluo River, China

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are emerging contaminants that pose a threat to the biodiversity of the Beiluo River, a polluted watercourse on the Loess Plateau impacted by diverse human activities. However, the occurrence, spatial distribution, and substitution characteristics of PFASs in this region remain unclear. This study aimed to unravel PFAS distribution patterns and their impact on the aquatic ecosystems of the Beiluo River Basin. The total PFAS concentration in the area ranged from 16.64–35.70 ng/L, with predominantly perfluorocarboxylic acids (PFCAs) and perfluorosulfonic acids (PFSAs), collectively contributing 94%. The Mantel test revealed threats to aquatic communities from both legacy long-chain (perfluorooctanoic acid and sodium perfluorooctane sulfonic acid) and emerging (6:2 fluorotelomer sulfonic acid, 2-Perfluorohexyl ethanoic acid, and hexafluoropropylene oxide dimer acid (Gen-X)) PFSAs. The canonical correspondence analysis ordination indicated that trace quantities of emerging PFASs, specifically 2-Perfluorohexyl ethanoic acid and hexafluoropropylene oxide dimer acid (Gen-X), significantly influenced geographical variations in aquatic communities. In conclusion, this study underscores the importance of comprehensively exploring the ecological implications and potential risks associated with PFASs in the Beiluo River Basin.

Responses of arid plant species diversity and composition to environmental factors

An oasis is a unique natural landscape in arid and semi-arid areas, significant for regulating regional microclimates and hydrological processes in deserts. However, little is known regarding the response of natural oasis plants communities to various environmental factors. Nineteen sample plots (50 m × 50 m) were selected in the Daliyabuyi Oasis in the Taklimakan Desert hinterland based on the location of groundwater monitoring wells and 76 vegetation quadrats (25 m × 25 m) were established. A two-way indicator species analysis, Mantel test, detrended correspondence analysis, canonical correspondence analysis (CCA), and hierarchical partitioning were used to provide an in-depth analysis of community classification, species composition, and environmental interpretation of the oasis. A generalized linear model was used to verify the results which showed that the current oasis community could be divided into four types according to the dominant species, which is controlled by soil moisture. Measurement of species composition and distribution of communities showed significant differences between species diversity of individual community types. Variations in groundwater depth affects patterns of species diversity which is sensitive to richness, while the degree of surface water disturbance affects the pattern of species evenness. Moreover, the CCA ordination map showed that community distribution and diversity characteristics have their own preferences in habitat gradients. The study concluded that the species dominance of the community and the composition and distribution are not dominated by a single factor. There are differences in the scale and effect of different water resource types in maintaining community characteristics.

Characterizing Uncertainty and Enhancing Utility in Remotely Sensed Land Cover Using Error Matrices Localized in Canonical Correspondence Analysis Ordination Space

In response to uncertainty in remotely sensed land cover products, there is continuing research on accuracy assessment and analysis. Given reference sample data, accuracy indicators are commonly estimated based on error matrices, from which areal extents of different cover types are also estimated. There are merits to explore the ways utilities of land cover products may be further enhanced beyond map face values and conventional area estimation. This paper presents an integrative method (CCAErrMat) for uncertainty characterization and utility enhancement. This works through reference-map cover type co-occurrence analyses based on error matrices localized in canonical correspondence analysis (CCA) ordination space rather than in geographic space to overcome the sparsity of reference sample data. The aforementioned co-occurrence analyses facilitate quantification of accuracy indicators, identification of correctly classified and perfectly misclassified pixels, and prediction of reference class probabilities, all at individual pixels. Moreover, these predicted reference class probabilities are used as auxiliary variables to formulate model-assisted area estimation, further enhancing map utilities. Extensions to CCAErrMat are also investigated as a way to bypass the pre-computing of map class occurrence pattern indices as candidate explanatory variables for CCAErrMat, leading to two variant methods: CCACCAErrMat and CNNCCAErrMat. A case study based in Wuhan municipality, central China was undertaken to compare the proposed method against alternative methods, including CCA-separate and CNN-separate. The advantages of CCAErrMat and CCACCAErrMat were confirmed. The proposed method is recommendable for characterizing uncertainty and enhancing utilities in land cover maps by analyzing locally constrained error matrices. The method is also cost-effective in terms of reference sample data, as requirements for them are similar to those for conventional accuracy assessments.

Relationship between species distribution of sandy alpine grasslands and microtopography in the source regions of Yangtze river

Dynamic of sandy alpine grasslands affect the progress and reversal of desertification in source regions of the Yangtse Rivers. To understand geomorphic driving mechanism of species distribution pattern, we examined the species compositions and delineated the most important landform factors influencing species distribution of sandy alpine grassland using two-way indicator species analysis (TWINSPAN), detrended correspondence analysis (DCA), and canonical correspondence analysis (CCA). Field survey were conducted in summer of 2016 using stratified random methods in hilly sloped lands, floodplains, foothills, and valley land of study region. In total, 29 plant species grouped into 27 genera and 16 families were identified. Leymus secalinus, Elymus dahuricus and Corispermum declinatum are the dominant species of sandy alpine grassland communities in different microtopography. The present vegetation reflected xerosere character, which indicated that desertification of alpine grassland is in progress. Standard frequency distribution of species varied with different microtopography, the proportion of dominant species was generally lower than rare species, and the vegetation community was in a highly successional stage. Seven groups were distinguished through TWINSPAN, distribution of which in the DCA ordination graph showed species with similar ecotype is clustered together. The results of the CCA ordination revealed that slope and aspect are the dominant factors among microtopography determining the species distribution of sandy alpine grassland.

Temporal distribution of fishery resources in Payra River: relationship with climatological changes, ecological assessment, and threat assessment

The Payra river is one of the large coastal rivers in Bangladesh which supports incredible fish species and has been affected by extensive human disturbance due to huge fishing pressure. The present study provides information about the temporal diversity of finfish and shellfish concerning climatological variables and ecological pollution along with threat assessment in the Payra river, Bangladesh. During the entire study, a total of 61 species including 56 finfish and 5 shellfish species were recorded under 22 families belonging to 11 orders. The order-wise fish species availability showed that the Perciformes (29.49%) was the dominant order based on species richness. Among them, 4 endangered, 6 vulnerable, 4 near threatened, 42 least concern, and 5 data deficient species were found. During the study period, the average Shannon-Weaver diversity index value was (3.33 ± 0.12) indicating a good spread of fish population in the Payra river. Average Margalef richness index value was found (7.60 ± 0.32), Pielou's evenness index (0.48 ± 0.05), and Simpson dominance index (0.93 ± 0.02) in the Payra river. The dominance and Richness index value indicates a clear water environment with slight pollution in the Payra river. Ten different kinds of fishing gears were identified under 3 major groups including 5 nets, 3 hooks and lines, and 2 traps. Canonical correspondence analysis ordination plot showed that rainfall was the most influencing driving force among the meteorological parameters. The cluster analysis based on the Bray-Curtis similarity matrix showed that the winter season formed a separate cluster. In the recapitulation, the Payra river is a highly productive system that provides a favorable environment for a large variety of finfish and shellfish species assemblages. The findings of the conducted study are expected to be helpful for the respective researchers, policymakers, managers, and conservationists for the sustainable management of this water body and the interconnected surrounding neighboring countries.

Effects of Soil Properties on the Distribution of Woody Plants in Communally Managed Rangelands in Ngaka Modiri Molema District, North-West Province, South Africa

Soil properties are important drivers of species distribution and community structure in grassland. This study was undertaken to assess the influence of soil properties on woody plant distribution around six selected communally managed rangelands in the District. At each communal rangeland, a total of 25 plots of 20 × 20 m were surveyed to record the density, frequency, and composition of woody species. Soil samples were collected for thirteen soil variables. A Tukey HSD (Tukey’s honestly significant difference) post hoc test was used to compare soil properties and canonical correspondence analysis (CCA) to relate the soil properties to the woody species distribution. The study recorded a total of 17 woody species in 9 families. Fabaceae was the most dominant family, and Senegalia mellifera was the most abundant and frequent encroaching species. Most of the species were native, whereas Prosopis velutina was the only invasive alien species recorded. Senegalia mellifera, P. velutina, and Terminalia sericea were considered the most encroaching in the study sites, with densities exceeding 2000 TE ha-1 (i.e., tree equivalent). CCA results exhibited the strong effect of soil variables on the distribution of woody plant species. CCA ordination analyses showed that K was the most influential soil variable on woody species distributions, followed by Mg, CEC, Na, pH, sand, clay and silt. In terms of woody distribution, the CCA diagram showed similarities between Disaneng, Logageng and Tshidilamolomo. This study provides baseline information on woody species diversity for future management of this ecosystem.

Drivers of Native Species Regeneration in the Process of Restoring a Dry Evergreen Forest from Exotic Tree Plantations in Northeastern Thailand

Establishment of exotic plantations is one of the most effective ways to induce natural regeneration for the restoration of degraded lands, as it has the potential to improve soil properties and creates favorable microclimates. This study aims to determine the effects of stand structure and composition as well as environmental factors under the canopies of three exotic plantations in northeastern Thailand on the regeneration of native species. For each plantation, we conducted three 10 m × 150 m transect lines with fifteen 10 m × 10 m subplots along a forest remnant gradient. The canonical correspondence analysis (CCA) was used to identify the environmental factors responsible for the differences in natural regeneration among these stands. Three exotic plantations had different stand structure in terms of number of tree species, basal area, and tree density but similar dominant native tree species. Across all stands, 74 native tree species, 60 genera, and 30 families were observed. Some physical and chemical properties in the topsoil were significantly different between species but similar among stands within a species. On the other hand, differences in environmental factors such as RLI were significant among species and stands within a species. The CCA ordination identified that the soil particles, soil pH, and light intensity were key factors influencing the native species composition, which could be categorized into three groups: drought-tolerant pioneer species; light-demanding pioneer species; and shade-tolerant climax species. However, most of the climax species were incapable of regenerating and maturing along the forest edge gradient to plantation stands. To accelerate the restoration process by converting these old exotic plantations to a dry evergreen forest, further research is required to determine the appropriate canopy management and/or dominant climax species for planting beneath their canopies.

入侵植物藿香蓟与常见伴生杂草的生态位特征

PDF HTML阅读 XML下载 导出引用 引用提醒 入侵植物藿香蓟与常见伴生杂草的生态位特征 DOI: 10.5846/stxb202104060881 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 浙江省自然科学基金项目(LY20C030002);浙江省教育厅一般项目(Y202045218) Niche characteristics of the invasive plant Ageratum conyzoides and its commonly associated weeds 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:基于传统生态位理论的生物入侵机制假说认为外来种和土著种生态位的差异是决定入侵成功与否和危害程度的关键。藿香蓟(Ageratum conyzoides L.)是一种在我国南方快速蔓延的恶性入侵种。为了了解藿香蓟与其他杂草在群落中的生态关系,探究造成藿香蓟成功入侵的可能机制及危害,在浙西南的丽水市开展了杂草群落调查,计算了藿香蓟和16种常见本地杂草的生态位宽度、生态位重叠和种间相关系数,并对主要物种进行典范对应分析(CCA)排序。结果表明(1)藿香蓟与常见本地杂草间的生态位重叠度显著高于本地杂草间的生态位重叠度,这与藿香蓟具有最大的生态位宽度有关;(2)藿香蓟与常见本地杂草的Pianka生态位重叠指数介于0.04-0.296之间,重叠度处于中下水平;(3)常见本地杂草对于藿香蓟的n-维超体积生态位重叠值显著高于藿香蓟对于常见本地杂草的n-维超体积生态位重叠值;(4)藿香蓟在CCA排序图上处于较中心的位置,说明其具有较高的中生性;不仅如此,外来杂草和本地杂草在排序图上充分混杂,说明外来种相对于本地种并无明显特化;(5)群落中大多数常见杂草间未出现显著种间负相关,仅7个种对显著正相关,大多数种对不相关。总的来说,丽水农村的杂草群落稳定较差,资源相对充足,种间生态位重叠较低,本地植物对于藿香蓟的竞争阻抗较小,加上藿香蓟本身较大的生态位宽度,导致了藿香蓟在本地区广泛而严重的入侵。 Abstract:According to the hypothesized mechanism of biological invasion, which is based on traditional niche theory, niche differentiation between alien species and native species is the key to the success of invasion and the damage it causes. Ageratum conyzoides L. is a malignant invasive species that is spreading rapidly in southern China. In order to understand the ecological relationships between A. conyzoides and native weeds in the community and to explore the possible mechanism of A. conyzoides invasion and its harmfulness, an investigation of the weed community was carried out in southwestern Zhejiang Province (28°06'-28°44'N, 119°32'-120°08'E) from 2014 to 2016. A total of 109 plots (1 m×1 m) and 286 plant species were investigated in the following habitats: roadside, abandoned farmland, streamside, and open forest. For each plot, all aboveground plant material was harvested, classified, and weighed according to species. In addition, slope, aspect, and altitude of the plot as well as the rate of sunshine arriving at the plot were measured. Moreover, pH value and the contents of total nitrogen, alkaline nitrogen, effective phosphorus, available potassium, and organic material in superficial soil (0-10 cm depth) of each plot were tested. Levin's niche breadth, Pianka's niche overlap, probability of n-dimensional niche overlap, and interspecific correlation coefficients of A. conyzoides and 16 common native weeds were calculated, and a canonical correspondence analysis (CCA) was conducted. The results showed that (1) the degree of niche overlap between A. conyzoides and common native weeds was significantly higher than that between any two native weeds, due to the largest niche breadth of A. conyzoides. (2) The Pianka niche overlap index between A. conyzoides and common native weeds was in the middle or lower level of 0.04-0.296. (3) The probabilities of n-dimensional niche overlap of common native weeds with A. conyzoides were significantly higher than those of A. conyzoides with common native weeds. (4) A. conyzoides was distributed in the central region of a CCA ordination chart, which indicated that A. conyzoides was a mesophilic species; moreover, exotic weeds (including A. conyzoides) and native weeds were fully mixed in the ordination chart, which indicated that there was no obvious specialization of exotic species relative to native species; and (5) there were no significantly interspecific negative correlations among the 17 common weed species; only 7 species pairs showed significantly positive correlation, and most species did not correlate with each other. In general, the weed community in the rural areas of southwestern Zhejiang Province is unstable, with relatively sufficient resources and low niche overlap among species. Low competition resistance from native plants and large niche width of A. conyzoides lead to extensive and serious invasion of A. conyzoides in the rural area of southwestern Zhejiang Province. 参考文献 相似文献 引证文献

1206. Effects of Climatic Variability on Lyme Disease Outbreaks in California

BackgroundClimate change has increased the risk of tick borne infections. The life cycle and prevalence of deer ticks are strongly influenced by temperature. Warmer temperatures associated with climate change are projected to increase the range of suitable tick habitats driving the spread of Lyme disease (LD). Short winters could also increase tick activity increasing the risk of exposure. This study examines the relationship between LD incidence and temperature-precipitation and their anomalies in CA counties.MethodsTrends and relationships of Lyme Disease (LD) cases and climatic factors were analyzed among the California counties from 2000 to 2019. Lyme disease tabulate data and climatic data were obtained from Centers for Disease Control, and NOAA, and Climate Data Guide respectively. Canonical correspondence analysis (CCA) was performed using variables: (i) LD cases, (ii) precipitation & anomaly, and temperature & anomaly. The CCA ordination explained the variability between LD cases and climatic variables. Biplots were used to visualize the associations between LD cases and climatic anomalies.ResultsWe compared the countywide LD cases in relation to climatic factors in California from 2000 to 2019. A total of 96 cases in 2000, 117 cases in 2009, and 144 cases in 2019 were reported in the 55 counties of California. Santa Clara reported the highest LD cases in 2003 (23 cases; 16%), followed by Los Angeles in 2013 (20 cases; 18%) and Santa Cruz in 2017 (19 cases; 13%). CCA ordination showed distinguishable clustering patterns between southern California counties (Santa Clara, Santa Cruz, Alameda, and San Diego) and northern coast and Klamath mountains range (Humboldt, Trinity, Shasta, and Siskiyou) regions (Fig. 1). Moderate mean annual temperature (56.5 °F - 62.5 °F) and temperature anomaly (3.8 °F - 5.5 °F) were the most important variable predictor for high LD outbreak. The CCA ordination shows the relationships between Lyme Disease and climatic variables for the 55 Counties of California. The bottom right circle represents Lyme cases positively correlated with temperature anomaly (3.8 °F - 5.5 °F) and moderate annual mean temperature (56.5 °F - 62.5 °F). The upper left circle represents Lyme cases negatively correlated with mean annual precipitation.ConclusionModerate temperature with low moist spell anomalies in the south neighboring CA counties showed a positive influence on LD outbreak. The climatic conditions in those areas suitable for Oak trees and masting acorn resulting in the establishment of tick and host (deer) populations. We recommend robust surveillance and lab testing for patients with a history of tick bites in these regions.Disclosures All Authors: No reported disclosures

Plant community C:N:P stoichiometry is mediated by soil nutrients and plant functional groups during grassland desertification

Grassland has sustained serious desertification due to inappropriate human activity in arid and semi-arid areas. This desertification has disrupted ecosystem structure and function. However, desertification on the grassland's C:N:P stoichiometry (Carbon, Nitrogen, and Phosphorus) are poorly understood, which undermines management and restoration of desertified grassland. To improve our knowledge, we studied a desertification gradient in Northeastern China's Horqin Sandy Land to determine the effects of desertification on ecosystem function, the plant community, and soil C:N:P stoichiometry. The soil and plant community C, N and P pools decreased during desertification. Under severe desertification, the soil C:N decreased by 17.4%, versus 39.2% for C:P and 50.1% for N:P. This implies non-proportional losses of soil organic C and nutrients, with the greatest loss for organic C, followed by total N and total P. Plant aboveground C:N and C:Pand belowground C:N increased, suggesting increased nutrient utilization efficiency. Canonical correspondence analysis ordination showed that soil N and P significantly affected the plant species composition, which was associated with plant C:N:P. The desertified grassland's fertility (especially N) directly determined the plant community C, N, and P concentrations and C:N:P ratios. The increased dominance of two psammophytes, Agriophyllum squarrosum and Artemisia halodendron decreased plant community C, N, and P concentrations, but increased C:N and C:P. Thus, plant community C:N:P stoichiometry was mediated by soil nutrients and plant functional groups driven by soil nutrient changes during desertification. The soil nutrient imbalance potentially changed plant community composition, this then altered the soil chemical composition because plant species differ in their element contents and litter inputs. Hence, species with high N content could improve grassland restoration by mitigating N limitations. The native psammophytes A. squarrosum and A. halodendron, with high stress resistance and resource utilization efficiency, could be applied in desertified grassland restoration.

The influence of environmental factors on species composition and distribution in a community forest in Northern Thailand

Understanding the environmental factors that influence tree species composition is essential for successful management of biodiversity and sustainable use of community forest resources. This study aims to assess tree species composition and distribution in the deciduous Ban Mae Chiang Rai Lum Community Forest in Northern Thailand and to analyze the influence of environmental factors on tree biodiversity in the forest. We conducted a stratified systematic sampling of the forest’s total area of 3925 ha, and twenty-five 0.16 ha survey plots were established in three different stands of the deciduous forests to estimate and characterize the difference in biological diversity among the stands. Canonical correspondence analysis (CCA) was used to investigate the environment factors affecting such differences in biodiversity of the stands. The results showed a high diversity of trees in the forest as 197 species, 144 genera, and 62 plant families were recorded. The CCA ordination identified the environmental factors—the most important of which were elevation, distance to streams, soil moisture, organic matter, and distance to communities—that significantly influenced the diversity and distribution of tree species (p < 0.05) in the community forest. Our findings indicate that the implementation of drought reduction measures such as building check dams, fire protection, and monitoring community forest-product usage would be recommended to further biodiversity conservation and the sustainable use of community forest resources.

Floristics and soil characteristics of Ohud mountain, Al-Madinah Al-Munawarah, Western Saudi Arabia

Ohud mountain is one of the main important historic sites in the Arab Peninsula, and it is distinguishable over the rest of the mountains in the region. No extensive floristic survey has been carried out on Ohud mountain because of the rugged topography of this mountain. The current study investigates the floristic diversity and the correspondence of environmental factors of the phytogeographical distribution of plants, based on the floristic analysis of the present region. The research question is about the relationships between the species diversity and the human impacts of populated area at lowlands around Ohud mountain. A total of 59 species belonging to 56 genera and 28 families were recorded. Asteraceae had the highest contribution, about 12% of the total plant species. The analysis of the life forms demonstrated the prevalence of therophytes (68%) followed by chamaephytes (24%), indicating the adaptation of these life forms to hyperarid conditions. The chorological analysis indicated the predominance of the bi-regional taxa over the other phytochoria. Most of the recorded plant species belong to Saharo-Arabian and Sudano-Zambezian (24%) phytochoria. TWINSPAN analysis was performed to detect the indicator species of different vegetation groups and confirmed by detrended correspondence analysis (DCA or DECORANA). It is concluded that species richness and diversity revealed clear variation along the mountain and among the studied sites. Plant species diversity and richness were more pronounced in the intermediate portion of the elevation gradients across the mountain, with a decrease in the high altitudinal belts. The decrease was also recorded at the lower altitudes, where human impacts clearly affected vegetation; leading to a decrease in alpha diversity. In addition, the beta diversity among moderately highlands and lowlands was considerably high indicating the heterogeneous species composition among the studied sites along mountain elevations. The general pattern of vegetation groups distribution is controlled by a number of environmental factors; such as latitude, longitude, elevation, organic matter and some anions and cations. A Canonical Correspondence Analysis (CCA) ordination revealed that the vegetation structure has a strong association with the latitude of the mountain followed by organic matter and Magnesium. It is recommended that the populated area should be subjected to restoration of mountain ecosystem that might be degraded by human activities.

Refining Land-Cover Maps Based on Probabilistic Re-Classification in CCA Ordination Space

Due to spatial inhomogeneity of land-cover types and spectral confusions among them, land-cover maps suffer from misclassification errors. While much research has focused on improving image classification by re-processing source images with more advanced algorithms and/or using images of finer resolution, there is rarely any systematic work on re-processing existing maps to increase their accuracy. We propose refining existing maps to achieve accuracy gains by exploring and utilizing relationships between reference data, which are often already available or can be collected, and map data. For this, we make novel use of canonical correspondence analysis (CCA) to analyze reference-map class co-occurrences to facilitate probabilistic re-classification of map classes in CCA ordination space, a synthesized feature space constrained by map class occurrence patterns. Experiments using GlobeLand30 land-cover (2010) over Wuhan, China were carried out using reference sample data collected previously for accuracy assessment in the same area. Reference sample data were stratified by map classes and their spatial heterogeneity. To examine effects of model-training sample size on refinements, three subset samples (360, 720, and 1480 pixels) were selected from a pool of 3000 sample pixels (the full training sample). Logistic regression modeling was employed as a baseline method for comparisons. Performance evaluation was based on a test sample of 1020 pixels using a strict and relaxed definitions of agreement between reference classification and map classification, resulting in measures of types I and II, respectively. It was found that the CCA-based method is more accurate than logistic regression in general. With increasing sample sizes, refinements generally lead to greater accuracy gains. Heterogeneous sub-strata usually see greater accuracy gains than in homogeneous sub-strata. It was also revealed that accuracy gains in specific strata (map classes and sub-strata) are related to strata refinability. Regarding CCA-based refinements, a relatively small sample of 360 pixels achieved a 3% gain in both overall accuracy (OA) and F0.01 score (II). By using a selective strategy in which only refinable strata of cultivated land and forest are included in refinement, accuracy gains are further increased, with 5–11% gains in users’ accuracies (UAs) (II) and 4–10% gains in F0.01 scores (II). In conclusion, on condition of refinability, map refinement is well worth pursuing, as it increases accuracy of existing maps, extends utility of reference data, facilitates uncertainty-informed map representation, and enhances our understanding about relationships between reference data and map data and about their synthesis.

Moss-inhabiting diatoms as ecological indicators in Neora Valley National Park (Eastern Himalaya), India

Terrestrial mosses which retain moisture provide a suitable ambience for diatoms colonization and suitable experimental platforms for observing climate change impact. The distribution and diversity patterns of such epibryic diatom communities are governed by various biotic and abiotic factors of moss habitats. The present study is first of ever attempt to investigate the moss-inhabiting diatoms in relation to various abiotic environmental variables from the Indian Himalayan Region (IHR). Samples were collected from 23 different sites in the Neora Valley National Park in Eastern Himalayas and analyzed through standard methods. Two-way indicator species analysis (TWINSPAN) and cluster analysis (CA) performed to classify the samples and habitats while direct canonical correspondence analysis (CCA) was used to determine the linkage between moss-inhabiting diatom species from various sample and abiotic environmental gradients. A total of 27 diatoms found colonizing on terrestrial moss patches from 23 sites of the park. CCA ordination plots showed that pH, conductivity and relative humidity were the primary factors influencing the diatom diversity and distribution, but altitude and temperature had no influence on the species distribution. But, correlation study on the average valve length of the most abundant and frequent taxa of Neora Valley National Park, i.e. Eunotia paludosa, E. bigibba and Hantzschia amphioxys, in relation to the environmental variables like, altitude, moisture content, relative humidity and temperature revealed a significant inference. The average valve length of these three diatoms decreases in warmer and drier climatic conditions at lower altitudes. Thus, these can be considered as potential indicator species to observe any climate change.

Canonical Correspondence Analysis Ordinations and Competitor, Stress Tolerator, and Ruderal Strategies of Coastal Dune Plants in South Korea

Lee, J.-S.; Son, D.-H.; Lee, S.-H.; Myeong, H.-H.; Cho, J.-S.; Lee, J.-C.; Lee, J.-Y.; Park, C.-S., and Kim, J.-W., 2020. Canonical correspondence analysis ordinations and competitor, stress tolerator, and ruderal strategies of coastal dune plants in South Korea. Journal of Coastal Research, 36(3), 528–535. Coconut Creek (Florida), ISSN 0749-0208.The distribution of plant communities in the sand dunes of the SW coasts of South Korea was studied, along with environmental factors and plant traits, by canonical correspondence analysis (CCA). The competitor, stress tolerator, and ruderal (CSR) ecological strategies were also evaluated. The coastal sand dune plants were classified into two plant trait groups in the CCA biplot diagram. First, vegetation was correlated with leaf dry weight, canopy height, specific leaf area, leaf dry matter content, and lateral spread. Second, it was correlated with the flowering period and flowering start. Coastal sand dune plants were classified into three soil factor groups in axes 1 and 2 of the CCA biplot diagram. First, the vegetation was correlated with total nitrogen (T-N), K+, Silt, Mg2+, Na+, and clay contents. Second, it was correlated with Ca2+. Third, it was correlated with the sand contents. To elucidate the relative significance of competition, stress, and disturbance in the distribution process of plant communities, the CSR distribution model was adopted. Many coastal plants (12 species) showed competitor-ruderal/competitor-stress-tolerant-ruderal strategies: Artemisia fukudo, Atriplex gmelinii, Carex kobomugi, Calystegia soldanella, Digitaria ciliaris, Linaria japonica, Messerschmidia sibirica, Oenothera bieenis, Salicornia europaea, Salsola komarovii, Suaeda glauca, and Suaeda maritima. The four species with stress-tolerant-competitor/competitor-stress-tolerant-ruderal strategies were Carex pumila, Imperata cylindrica var. koenigii, Limonium tetragonum, and Zoysia sinica. Conyza canadensis, Ischaemum anthephoroides, Phragmites communis, and Vitex rotundifolia displayed competitor/stress-tolerant-competitor, competitor-ruderal, stress-tolerant-competitor, and C/SC strategies, respectively. The differences in distribution and restoration patterns of the CCA diagrams and CSR triangles may be attributable to different adaptions of plant traits or soil factors.

被遗忘的城市“生境”:重庆市墙体自生植物调查分析

PDF HTML阅读 XML下载 导出引用 引用提醒 被遗忘的城市“生境”:重庆市墙体自生植物调查分析 DOI: 10.5846/stxb201804130848 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划课题（2017YFC0505705）；国家自然科学基金项目（51408584） Forgotten urban habitats: Analysis of spontaneous vegetation on the urban walls of Chongqing City 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:被称为"钢筋水泥森林"的现代城市存在大量的墙体，包括建筑外墙、独立围墙、挡土墙等类型。通常情况下，这些完全硬质化的界面不会被认作为生境或栖息地。以典型山城重庆市为例，探索城区范围内墙体成为城市生境的可能性。于2017年9-11月对重庆主城区共120块墙，包含359个4×1 m小样方，调查墙面上自生植物的物种、覆盖度等信息；记录墙体4类特征共22个因子作为生境影响因素；并采用方差分解和典范对应分析（CCA）排序法研究影响因素与自生植物组成和分布的关系。结果表明：（1）市区墙境自生植物丰富，共记录到70科149属193种，以菊科植物种类最丰富，其次是禾本科和荨麻科。优势种包括蜈蚣草（蕨类）、井栏边草（蕨类）、构树幼苗（乔木）、贯众（蕨类）和黄葛树幼苗（乔木）。相比平面环境的自生植物以旱生为主，墙体上喜阴湿的蕨类植物占明显优势，反映出墙体作为生境的独特性，可以作为城市生态空间的有效补充。（2）墙体4类特征共解释自生植物组成与分布变化的14.4%，植物传播、定植与构建是一个综合复杂的过程，受各种随机因素影响；此外，本文所选因素也未考虑更大尺度的周边景观等因素。所有因子中，墙体高度、藤蔓覆盖度和墙体遮阴率是影响植物变化的主要因子，且与CCA排序第1轴相关性最强。这些因子均与墙体自身湿度有关，表明水分在决定墙面植物组成与分布起主要作用，植物在墙面沿水分呈梯度分布。讨论了本研究对现代城镇绿化的启示，从自然做功的角度提升城市生态系统服务，为城市生态设计与低成本管理提供科学依据。 Abstract:Cities are known as "concrete forests," and they have substantial walls of many types, including buildings, free-standing (boundary), and retaining (those used for reinforcing slopes or to confine river channels). Generally, these completely concrete walls are not considered as habitats. Using a typical mountainous city, Chongqing, as the case study, we aimed at exploring the possibility that urban walls can act as habitats in cities. From September to November 2017, we surveyed 120 walls, across 359 sampling quadrates, to obtain spontaneous vegetation data and associated wall characteristics. The effects of wall characteristics on the variation of spontaneous vegetation was calculated using variance partitioning and canonical correspondence analysis (CCA) ordination method. Vascular plants totaled 193 species in 149 genera from 70 families. The Compositae family had the greatest number of species and was followed by Gramineae and Urticaceae. The dominant species included Pteris vittata, Pteris multifida, seedlings of Broussonetia papyrifera, Cyrtomium fortune, and seedlings of Ficus virens. They occurred in more than 40% of all quadrates. The wall vegetation showed a diverse range of plant life-forms (i.e., woody, fern, and vine). Compared to xerophytes that dominate planar environments, more fern species inhabited the walls. This finding is consistent with that of other studies. This reflects the uniqueness of walls as habitats, and urban walls can act as a valuable complement to urban ecological spaces. The explanatory power of all four wall characteristics was low (14.4%). The spontaneous species assemblage was a complex process, and it was influenced by environmental stochasticity. Additionally, the unexplained portion may come from the influence of the large-scale landscape context. Among all the variables, wall height, vine coverage, and wall shade were the most important factors that influenced vegetation composition and distribution, and they had the highest correlation with the first constrained axis of the CCA ordination. All variables were relevant to wall humidity. This indicates that moisture plays a decisive role in structuring vegetation on urban walls. Lastly, we discussed the implications of this study on greening and landscaping contemporary cities. Urban biodiversity improvement can be done by "allowing nature to work". Our study also provides scientific support for urban ecological design and low-cost management. 参考文献 相似文献 引证文献

Classification and ordination of the main plant communities of the Eastern Hajar Mountains, Oman

This article presents a quantitative description of the plant communities of the Eastern Hajar Mountains of Oman and the primary environmental variables affecting their composition and distribution. Species inventories and environmental data were collected from 110 vegetation plots covering elevation from 1000 m to the highest point in the mountains at about 2200 m. Measurements of 12 environmental variables were used in the analysis: aspect, slope, annual rainfall, soil pH, salinity, soil nutrients (N, P, K, Ca) and soil texture (clay and silt). Two Way Indicator Species Analysis (TWINSPAN) classification, Detrended Correspondence Analysis (DCA) and Canonical Correspondence Analysis (CCA) ordinations showed four well-distinguished plant communities. Although some species overlap occurred in the transition zones between the communities, these plant communities were characteristic for their zones. Annual rainfall, total nitrogen and total calcium were the most important environmental factors affecting the distribution of plant communities. The high-altitude community was always distinctly identified using all different data treatments, while the lower-altitude communities tended mostly to overlap. Any grazing effect on plant community distribution appears to be overridden by the other environmental variables.

Phylogeny and distribution of Bradyrhizobium symbionts nodulating cowpea (Vigna unguiculata L. Walp) and their association with the physicochemical properties of acidic African soils

In the N2-fixing symbiosis, the choice of a symbiotic partner is largely influenced by the host plant, the rhizobial symbiont, as well as soil factors. Understanding the soil environment conducive for the survival and multiplication of root-nodule bacteria is critical for microbial ecology. In this study, we collected cowpea-nodules from acidic soils in Ghana and South Africa, and nodule DNA isolates were characterized using 16S–23S rRNA-RFLP, phylogenetic analysis of housekeeping and symbiotic genes, and bradyrhizobial community structure through canonical correspondence analysis (CCA). The CCA ordination plot results showed that arrow of soil pH was overlapping on CCA2 axis and was the most important to the ordination. The test nodule DNA isolates from Ghana were positively influenced by soil Zn, Na and K while nodule DNA isolates from South Africa were influenced by P. The amplified 16S–23S rRNA region yielded single polymorphic bands of varying lengths (573–1298bp) that were grouped into 28 ITS types. The constructed ITS-dendrogram placed all the nodule DNA isolates in five major clusters at low cut-off of approx. 0.1 Jaccard’s similarity coefficient. The phylogenetic analysis of 16S rRNA and housekeeping genes (glnII, gyrB, and atpD) formed distinct Bradyrhizobium groups in the phylogenetic trees. It revealed the presence of highly diverse bradyrhizobia (i.e. Bradyrhizobium vignae, Bradyrhizobium elkanii, Bradyrhizobium iriomotense, Bradyrhizobium pachyrhizi, and Bradyrhizobium yuanmingense) together with novel/unidentified bradyrhizobia in the acidic soils from Ghana and South Africa. Discrepancies noted in the phylogenies of some nodule DNA isolates could be attributed to horizontal gene transfer or recombination.

Spatial pattern of plant diversity in a group of uninhabited islands from the perspectives of island and site scales

Uninhabited islands are important for providing isolated habitats for unique biological resources, and revealing the spatial pattern of plant diversity is of great significance for the island biodiversity conservation. A total of 15 uninhabited islands in Miaodao Archipelago, a group of typical uninhabited islands in North China, were selected as the study area. The multiple gradients at island and site scales were identified and quantified based on field investigation and remote sensing methods, and seven “from macro to micro” aspects, including morphology, proximity, landscape, terrain, atmosphere, soil, and vegetation, were selected to cover all aspects of factors influencing the plant diversity. Then, the single and comprehensive effects of the multiple gradients on the spatial pattern of plant diversity at the dual scales were analyzed using methods of regression analysis and canonical correspondence analysis ordination. Results indicated that 130 plant species were recorded. The species accumulation curves proved the sufficiency of the numbers of sampling sites and islands to represent the overall characteristics of plant diversity. The species composition on the uninhabited islands possessed common characteristics with the neighboring inhabited islands and mainland, meanwhile, showed unique features on the dominant species. The α diversity showed distinct spatial heterogeneities at the dual scales; the β diversity indicated the great difference of species composition within an island and among different islands. At island scale, island area, vegetation condition, and terrain complexity contributed the most to the spatial pattern of plant diversity. At site scale, biodiversity indices changed irregularly along the multiple gradient factors, yet all aspects of gradients showed significant effects on the species composition and distribution. The island area played a fundamental role in determining the α diversity at island scale and generating the β diversity within an island, however, was not significantly correlated with the diversity at site scale.