Principal Component Analysis Ordination Research Articles

Assessing plant utilisation by communities bordering a protected area in Zimbabwe using utilitarian diversity metrics

Protected areas and their peripheries harbour biodiverse ecosystems which underpin ecosystem service provision to local communities. Understanding the relationship between the species contained within these ecosystems and the utilitarian services they provide is important. However, there is a shortage of quantitative methods for assessing species’ utilitarian roles. We used a dendrogram-based method to quantify utilitarian diversity and an ordination method to determine co-occurrences in three sites at the periphery of Gonarezhou National Park, in Zimbabwe. The use categories for the plants were determined using household questionnaire surveys, and vegetation data was collected via standard plotless sampling techniques. There was higher plant diversity in the sites adjacent to the protected area, i.e. Malipati communal area (S = 45; Simpson’s index = 0.7271) and Gonakudzingwa farms (S = 50; Simpson’s index = 0.9351), with the lowest diversity recorded at the site far from the park, i.e. Chomupani communal area (S = 25; Simpson’s index = 0.6305). Utilitarian diversity was also highest in the areas adjacent to the protected area, with Malipati and Gonakudzingwa having values of 22.2 and 21.4, respectively, while Chomupani attained 20.6. A principal component analysis ordination indicated which utilitarian species occurred in the same areas. Our results contribute to plant conservation by highlighting the utilitarian relationships of species at protected area peripheries. This allows planners and conservationists to set conservation priorities to avoid losing species that contribute the most to ecosystem service provision.

Data-specific substitution models improve protein-based phylogenetics.

Calculating amino-acid substitution models that are specific for individual protein data sets is often difficult due to the computational burden of estimating large numbers of rate parameters. In this study, we tested the computational efficiency and accuracy of five methods used to estimate substitution models, namely Codeml, FastMG, IQ-TREE, P4 (maximum likelihood), and P4 (Bayesian inference). Data-specific substitution models were estimated from simulated alignments (with different lengths) that were generated from a known simulation model and simulation tree. Each of the resulting data-specific substitution models was used to calculate the maximum likelihood score of the simulation tree and simulated data that was used to calculate the model, and compared with the maximum likelihood scores of the known simulation model and simulation tree on the same simulated data. Additionally, the commonly-used empirical models, cpREV and WAG, were assessed similarly. Data-specific models performed better than the empirical models, which under-fitted the simulated alignments, had the highest difference to the simulation model maximum-likelihood score, clustered further from the simulation model in principal component analysis ordination, and inferred less accurate trees. Data-specific models and the simulation model shared statistically indistinguishable maximum-likelihood scores, indicating that the five methods were reasonably accurate at estimating substitution models by this measure. Nevertheless, tree statistics showed differences between optimal maximum likelihood trees. Unlike other model estimating methods, trees inferred using data-specific models generated with IQ-TREE and P4 (maximum likelihood) were not significantly different from the trees derived from the simulation model in each analysis, indicating that these two methods alone were the most accurate at estimating data-specific models. To show the benefits of using data-specific protein models several published data sets were reanalysed using IQ-TREE-estimated models. These newly estimated models were a better fit to the data than the empirical models that were used by the original authors, often inferred longer trees, and resulted in different tree topologies in more than half of the re-analysed data sets. The results of this study show that software availability and high computation burden are not limitations to generating better-fitting data-specific amino-acid substitution models for phylogenetic analyses.

柯-青冈常绿阔叶林优势树种叶片性状变异及适应策略

PDF HTML阅读 XML下载 导出引用 引用提醒 柯-青冈常绿阔叶林优势树种叶片性状变异及适应策略 DOI: 10.5846/stxb202103100659 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 湖南省教育厅重点项目（17A227）；国家自然科学基金青年科学基金项目（31901136） Variation in leaf functional traits and adaptation strategies of dominant tree species in a Lithocarpus glaber-Cyclobalanopsis glauca evergreen broad-leaved forest 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:厘清叶片功能性状的变异及性状间的权衡关系，对揭示植物对环境变化的响应及适应策略具有重要意义。以中亚热带柯(Lithocarpus glaber)-青冈(Cyclobalanopsis glauca)常绿阔叶林为对象，测量了1 hm2固定监测样地内6个优势树种的叶面积(LA)、比叶面积(SLA)、干物质含量(LDMC)、叶片厚度(LT)、叶片碳(LC)、叶片氮(LN)、叶片磷(LP)含量和叶片碳氮比(LC ∶ LN)8个功能性状，采用多重比较、主成分分析(PCA)法分析了群落叶片功能性状的生活型、种内和种间变异及性状间关系。结果表明：(1)群落内叶片功能性状种内、种间差异显著，变异中等(CV： 0.02-0.59)，其结构性状的可塑性较化学性状保守，变异格局符合"性状空间变异分割假说"；针叶树种的LA、SLA显著低于阔叶树种，常绿树种的LC和LDMC最小，而落叶树种的SLA、LN和LP最大以及LT和LC ∶ LN最小。(2)群落叶片功能性状变异主要来源于生活型和种间变异，种内变异亦有显著贡献；生活型对多数性状的贡献率较大，其对LDMC、LC ∶ LN的贡献分别高达93.11%和91.76%；种间变异(LDMC除外)对结构性状的贡献率均高于化学性状；种内变异对LP的贡献率(23.66%)较种间变异高。(3)叶片性状之间多表现出显著相关关系，针叶树和阔叶树在PCA排序图中聚集于不同区域，叶经济型谱在柯-青冈群落中具有适用性。不同树种通过叶片结构、化学性状之间的权衡策略来适应环境变化，从而实现群落物种共存。结果可为理解森林群落物种的环境适应策略、预测群落动态变化和制定植被恢复措施提供科学依据。 Abstract:Elucidating the variation in leaf functional traits and the trade-off relationships among those traits are of great significances to reveal the response mechanism's and adaptation strategies of plants towards changing environment. The variation of plant functional traits organically links the species adaptation strategy with the ecosystem functions and processes, and the ranges including interspecific and intraspecific variations vary with species and are closely related to environmental gradients. Meanwhile, the leaf economics spectrum (LES) at the global scale can reflects the trade-off relationships between the main structural, chemical and physiological traits. However, local community puts environmental factors and functional traits in the same system, and the main reasons responsible for the variation in functional traits and the applicability of LES still need to be deeply investigated. In this study, we collected 8 leaf functional traits of 6 dominant tree species in a 1 ha permanent monitoring plot of a Lithocarpus glaber-Cyclobalanopsis glauca subtropical evergreen broad-leaved forest, and the studied traits included leaf area (LA), specific leaf area (SLA), leaf dry matter content (LDMC), leaf thickness (LT), leaf carbon (LC), leaf nitrogen (LN), leaf phosphorus (LP) content and carbon-nitrogen ratio (LC :LN). We used multiple comparison and principal component analysis (PCA) to explore the variation in leaf functional traits at the interspecific, intraspecific and life form levels, and to analyze the relationship among those functional traits. The results showed that:(1) Leaf functional traits were significantly different at the intraspecific and interspecific levels in this community. There was a moderate variation with a coefficient variation (CV) ranging from 0.02 to 0.59, and the structural traits were more conservative than chemical traits. The variation pattern of leaf functional traits conformed to "a spatial trait variance partitioning hypothesis". Leaf functional traits significantly differed among life forms, with lower SLA and LA for coniferous tree species compared to those for broad-leaved tree species, lowest LC and LDMC for evergreen trees, yet the deciduous tree species exhibited the highest SLA, LN and LP along with the lowest LT and LC :LN. (2) Life form and interspecific differences contributed the most to the variation in leaf functional traits, and intraspecific differences also contribute significantly to those variations with lower contribution rate. Life forms had relative higher contribution to the variation in most functional traits with the contribution rate reaching 93.11% and 91.76% for LDMC and LC:LN, respectively. The contribution rate of interspecific variation (except LDMC) to structural traits was higher than that to chemical traits. Intraspecific variation had a higher contribution rate to LP (23.66%) than interspecific variation. (3) There was a significant correlation between leaf functional traits. Conifers and broad-leaved trees clustered in different areas of PCA ordination chart. The leaf economics spectrum was applicable in the subtropical evergreen broad-leaved forest, and diverse tree species could coexist in this community by the trade-off strategies among leaf structural and chemical traits. The results could provide a scientific basis for understanding the adaptation strategies of diverse tree species to environment, predicting the dynamic changes of community and formulating vegetation restoration strategy. 参考文献 相似文献 引证文献

Meta-analysis of Cryogenian through modern quartz microtextures reveals sediment transport histories

ABSTRACT Quantitative analysis of quartz microtextures by means of scanning electron microscopy (SEM) can reveal the transport histories of modern and ancient sediments. However, because workers identify and count microtextures differently, it is difficult to directly compare quantitative microtextural data analyzed by different workers. As a result, the defining microtextures of certain transport modes and their probabilities of occurrence are not well constrained. We used principal-component analysis (PCA) to directly compare modern and ancient aeolian, fluvial, and glacial samples from the literature with nine new samples from active aeolian and glacial environments. Our results demonstrate that PCA can group microtextural samples by transport mode and differentiate between aeolian transport and fluvial and glacial transport across studies. The PCA ordination indicates that aeolian samples are distinct from fluvial and glacial samples, which are in turn difficult to disambiguate from each other. Ancient and modern sediments are also shown to have quantitatively similar microtextural relationships. Therefore, PCA may be a useful tool to constrain the ambiguous transport histories of some ancient sediment grains. As a case study, we analyzed two samples with ambiguous transport histories from the Cryogenian Bråvika Member (Svalbard). Integrating PCA with field observations, we find evidence that the Bråvika Member facies investigated here includes aeolian deposition and may be analogous to syn-glacial Marinoan aeolian units including the Bakoye Formation in Mali and the Whyalla Sandstone in South Australia.

Regeneration of black ash (Fraxinus nigra Marsh.) in hardwood swamps of the Great Lakes – St. Lawrence Forest Region

An inductive, ordination-based approach was used to explore patterns in the microenvironment and natural regeneration of black ash across a range of representative stands in the central Ontario portion of the Great Lakes -St. Lawrence Forest Region (GLSL) near Lake Nipissing, Ontario, Canada. The objective of this study was to describe patterns of regeneration of black ash and determine the associations between multiple indicators of black ash regeneration success and biotic and abiotic factors. Using a randomized sampling design with specific selection criteria, 12 black ash stands were sampled, each with three 400 m2 circular sample plots that contained three 4 m2 sub-plots. A suite of environmental variables such as elevation, topographic wetness index, slope, and soil characteristics (percent moisture, pH, total nitrogen, exchangeable phosphorus, potassium, magnesium) were determined for each stand. Variables capturing regeneration potential, including density, diameter, and height of all germinants, seedlings, saplings and sprouts were also collected. A sample of 15 dominant or co-dominant trees in each stand, as well as numerous black ash seedlings, saplings and sprouts were examined using dendrochronological methods to estimate ages. Principal component analysis ordinations were performed exploring the variation in environment and black ash regeneration variables among the stands. High soil moisture and the presence of canopy gaps, (as indicated by high standard deviation of canopy closure), were key variables associated with greater abundance of regeneration. Black ash was the dominant species in all stands, which were also generally characterized by a common reverse-J diameter distribution. It was observed that black ash in the sapling layer reached substantial ages (up to 60 years), indicating they are capable of withstanding long periods of suppression below the canopy. Collectively, these findings suggest that black ash-dominated stands in the study area are regenerating in multiple cohorts. Based on these patterns, it appears that regeneration in these stands is occurring through gap-phase mechanisms, suggesting single tree selection as the best management option for black ash in the GLSL.

Standing Vegetation Exceeds Soil Microbial Communities in Soil Type Indication: A Procrustes Test of Four Salt-Affected Pastures

Organisms with different life histories are able to act as indicators of different characteristics of their environment. Here, we compared the precision of habitat indication by the vegetation and soil microbial communities in four salt-affected pastures: annual open salt sward, Pannonic Puccinellia limosa hollow, Artemisia saline puszta and grassy saline puszta. Dissimilarity of habitats was evaluated by standardized principal component analysis (PCA) based on four different datasets: catabolic profiles of microbial communities in June (a) and September (b), composition of vascular vegetation (c) and physical and chemical properties of the soil (d). Procrustes analysis was used to quantify the resemblance between pairs of PCA ordinations based on soil properties (d) and various biotic communities (a, b, c). PCA ordination based on vegetation most closely matched the soil data-based ordination, thus vegetation appears to better indicate habitat conditions than soil microbial communities do. For microbial communities, a better agreement with the soil data-based ordination was reached in September than in June. Most probably, the long-lived sedentary habit of perennial plants in these communities requires adaptation to long-term average habitat conditions. In contrast, short-lived soil microbes can quickly follow environmental changes, thus the composition of soil microbial communities better reflect actual soil conditions.

Functional relationship between woody plants and insect communities in response to Bursaphelenchus xylophilus infestation in the Three Gorges Reservoir region.

To study the effect of the invasion of Bursaphelenchus xylophilus on the functional relationship between woody plants and insect communities, the populations of tree species and insect communities were investigative in the Masson pine forests with different infestation durations of B. xylophilus. In this study, the number of Pinus massoniana began to decrease sharply, whereas the total number of other tree species in the arboreal layer increased gradually with the infestation duration of B. xylophilus. The principal component analysis ordination biplot shows that there was a significant change in the spatial distribution of woody plant species in different Masson pine forest stands. Additionally, a total of 7,188 insect specimens were obtained. The insect population showed an upward trend in stand types with the increase of pine wilt disease infection periods, which demonstrated that the insect community had been significantly affected by the invasion of B. xylophilus. However, the insect diversity indexes were not significantly different among Masson pine forest stands. The structure of insect functional groups changed from herbivorous (He) > omnivorous (Om) > predatory (Pr) > parasitic (Pa) > detritivorous (De) in the control stand to He > Pa > Om, De > Pr after B. xylophilus infestation in the forests. The results showed that the populations of He, Pa, and De increased after the invasion of B. xylophilus, but the populations of Pr decreased. Moreover, the redundancy analysis ordination biplots reflected the complicated functional relationship between woody plant communities and insects after the invasion of B. xylophilus. The present study provides insights into the changes in the community structure of woody plants and insects, as well as the functional relationship between woody plant communities and insect communities after invasion of B. xylophilus.

The influence of environmental factors on the distribution and composition of plant species in Oued Charef dam, northeast of Algeria

Abstract. Moualki N, Boukrouma N. 2021. The influence of environmental factors on the distribution and composition of plant species in Oued Charef dam, North East of Algeria. Biodiversitas 22: 346-353. Identification of the primary factors that influence the ecological distribution of species groups is important to managers of Oued Charef dam in northern Algeria. This study aimed to identify main ecological species groups, describe the site conditions associated with these species groups, and the relationships between environmental factors and the distribution of ecological species groups using Ward’s cluster analysis for classification and principal component analysis (PCA). For this purpose, 50 plots (200 m2 each) were sampled using the Braun- Blanquet method. Soil samples were collected and analyzed to study soil properties. Multivariate analysis methods were used to classify and determine the relationship between species composition and environmental factors and to recognize ecological species groups. The R i386 (version 4.0.3) software was used for data analyzing. Ward's cluster analysis when applied on terrestrial species data gives three groups distinctly distributed on ordination plan. In cluster groups of terrestrial species Group (1) is dominated by Daisies chrysanthemum, Group (2) by Cynodon dactylon L, and Group (3) dominated by Fumana thymifolia. The groups of terrestrial species are readily superimposed on PCA ordination plane. The most important environmental factors associated with terrestrial species composition in Oued Charef dam communities were conductivity (EC), FSA, FSI, clay, salinity, phosphorus (PO4), TN (nitrogen), nitrates (NO3), and nitrites (NO2). While among the edaphic factors only pH showed a negative correlation to plant species this may due to the anthropogenic disturbances however further studies are needed to explore the rest of parts of the said regions. This study gives important insights on ecological relationships between plant biodiversity and soil chemical in a primary wetland ecosystem in northeast of Algeria.

Properties of alluvial and non-alluvial soils in fragmented mixed deciduous forest patches in southern Québec, Canada

Soils and tree species are studied in mixed temperate forests along the Coaticook River (Southern Québec, Canada) to examine the effect of frequent floods on soil properties and vegetation. The soils and tree stands are located in the flood zones (FZ) and no-flood zones (NFZ) in 49 quadrats. Different statistical analyses were carried out on soils and tree data, including ANOVA, Kruskal-Wallis, Principal Component Analysis (PCA) and Canonical Correlation Analysis (CCA) ordinations. The variables used for soil property analysis were pH, total organic carbon, total nitrogen, C/N ratio, total sulfur, Fe + Al, texture, bulk density, soil moisture, and soil biomass (litter), while the vegetation variables consisted of the number of tree species, their density, and the diameter and measurement of the basal area. The soil property analyses show significant differences between alluvial and non-alluvial soils, including organic carbon, nitrogen, pH, Fe + Al, soil moisture, texture, and plant litter thickness (cm). The PCA ordination realized on soil variables shows two distinct axes, including a first axis (PC1) grouping TOC, TN, TS, soil moisture and pH variables, and accounting for 35% of the total variation, and a second axis (PC2) that includes textural variables (clay and silt) and representing 21% of the total variability. The species richness and diversity analyses did not show statistical differences for the tree species between the two zones that were analyzed (FZ and NFZ), although some tree species are associated with the specific edaphic conditions. The results of the CCA ordination conducted on soil and vegetation data revealed that the tree communities have a significant response to soil variables and flood frequency. All the variables that were studied account for 40% of the variation in species composition based on soil properties. This study shows that successive floods affect soil properties, including depletion of soil organic carbon and nitrogen, and that floods and soil conditions can have a direct effect on the distribution of certain tree species.

Evolution Characteristics of Groundwater Level and its Relation to Low-Carbon Development in Southern Horqin Sandy Land, China

With remarkable impacts of climate change and anthropogenic activities, the Horqin Sandy Land presents southward invading trend, which threatens the city development in southern water shortage cities. Therefore, to prevent the sandy land from southward invading and to protect the city water security, it is of great importance to reasonably explore the groundwater in southern Horqin Sandy Land. Based on the data of groundwater level, precipitation, temperature, population, etc. from 1997 to 2016 in Kangping County, this paper focused on evolution characteristics analysis and genesis analysis of the groundwater level in Kangping County. The results show a significant decrease of groundwater level from 2014 to 2016, with a substantial increase of population in 2015. The PCA (Principal Component Analysis) ordination showed that the groundwater level in the south, middle and north of Kangping county was positively related to each other. The groundwater level had a significantly negative correlation with population and temperature, while a remarkably positive correlation with precipitation. It is calculated that the annual extraction of groundwater by thermal power generation in Kangping County releases about 18,740 t of CO2. As population increases, the groundwater level will continue to decrease, the carbon emissions will increase as well. It is suggested to reduce thermal power generation pattern by developing the abundant local wind and solar energy resources, thus achieving the low-carbon development in water shortage cities.

Brotherhoods of relative entropy, boolean operators and principle component analysis for a gradient of living communities

It is well known that gradient values of the living communities are the most important and valuable data to examine and explain community-environmental relationships. On this context, the purpose of the present study is to find an answer to the question that is how to generate a gradient of living communities along the PCA (Principal Component Analysis) ordination axes by using relative entropy (D[p(x) | |q(x)]), a measure of the non-symmetric difference between two probability distributions, p and q. A hypothetic data matrix composed of 3 plant communities was subjected to relative entropy. Relative entropy could not be calculated from original data since the hypothetic data matrix includes zero values. The data matrix was, therefore, re-arranged by increasing the marginal entropy of each of the communities. Thus shaded relative entropies (D∎[p(x) || q(x)]) among the communities were successfully calculated. Next, the locations of the resulted matrix in which each community shares a cell with itself were analyzed using Boolean Operators and principle component analysis (PCA). Lastly, the last PCA was applied in order to determine the locations of the plant communities along the ordination axes. The results of such approach were compared to the results obtained from the original data by using cluster analysis. The results were found very similar as a result of this comparison and, it was formed an opinion to be able to successfully use the combinations of shaded relative entropy and Boolean operators for a gradient of the living communities along the PCA ordination axes.

Weed species composition and density under conservation agriculture with varying fertiliser rate

Conservation agriculture (CA) is a sustainable management system that optimises yield while reducing input costs. However, reduction in tillage intensity and frequency as practised under CA generally alters weed densities and composition. The objective of the study was to evaluate the effect of tillage, cropping system and fertiliser rate on weed density and diversity under CA systems compared with conventional tillage (CT). An on-station field trial with a split-plot, randomised complete block design, was used and included two tillage systems, three cropping systems and two fertiliser levels. Reduced tillage had significantly (p < 0.05) higher weed density (42 m−2) but lower weed biomass (154 g m−2) in contrast to CT with lower weed density (36 m−2) and higher weed biomass (242 g m−2). In a principal component analysis ordination, Datura ferox and Tribulus terrestris were more strongly associated with high fertiliser rate, whereas Zinnia peruviana was associated with CT. The increase in weed density and diversity under reduced tillage is likely to restrain the adoption of CA. Therefore, there is a need for alternative weed management options depending upon the weed spectrum, cropping system and fertiliser management.

Restoration prioritization for industrial area applying multiple potential natural vegetation modeling

Scaling‐up ecological restoration demands the involvement of private sector actors. Experience regarding science‐based habitat restoration programs in the sector should be made available to support further joint projects. In our case, hierarchical restoration prioritization was applied to select best target for habitat reconstruction at a Hungarian industrial area. Multiple potential natural vegetation model, a novel approach, supported restoration prioritization satisfying both ecological (sustainability and nature conservation value) and other needs (feasibility, rapid green surface, amenity, and education value). The target that met all priorities was the open steppe forest that has a mosaic arrangement with open and closed sand steppes. The potential area of this xero‐thermophile oak wood is expected to expand in Hungary with climate change, therefore the selected target has a likelihood of long‐term sustainability, if established. A matrix of sand steppes was created first at the factory area in 2014–2015, and tree and shrub saplings were planted in this matrix. The seeding induced rapid changes in vegetation composition: the second year samples became close to reference sand steppes in the principal component analysis ordination space. Tree and shrub survival was species dependent, reaching a maximum of 52 and 73% for tree and shrub species, respectively. One tree and 2 shrub species did not survive at all. Altogether 53 of 107 target species have established. So far, restored vegetation development confirmed the suitability of the applied hierarchical prioritization framework at factory scale.

The PCA index for measuring functional diversity and its application to Juglans mandshurica communities in the Beijing mountains, China

Methods for measuring functional diversity are essential for functional studies of plant communities. A useful method, the PCA index, based on principal component analysis ordination of functional trait data was introduced and applied to functional diversity analysis of Juglans mandshurica communities in the Beijing Mountains. Thirty-five [Formula: see text] quadrats were established in Juglans mandshurica communities. Species composition, functional traits and environmental factors were measured and recorded. The four common indices, FAD, MFAD, FDp and FDc, were used and compared with the PCA index in the analysis. The results showed that the PCA index was successful in quantifying functional diversity and describing its relationships with environmental variables; therefore, it was an effective index in functional diversity analyses. Functional diversity in Juglans mandshuricacommunities varied widely. Elevation and aspect were the key factors affecting functional diversity in communities. Functional diversity increased with elevation increases and with the change in aspect from North to South. Functional diversity was significantly correlated with species richness and heterogeneity.

Vegetation composition differentiation and species-environment relationships in the northern part of Isfahan Province, Iran

A considerable proportion of Iran’s territory is covered with arid and semi-arid rangelands and mismanagement and overexploitation of those rangelands have resulted in serious ecological degradation. Thus, the need is pressing to examine the present species composition and the relationships with environmental factors for providing the needed scientific references to species conservation and ecological rehabilitation efforts. The aims of this study were to examine the species composition and to delineate the most important factors influencing the distributions of plant species and groups in the northern rangelands of Isfahan Province (Iran) using two-way indicator species analysis (TWINSPAN), detrended correspondence analysis (DCA), principal component analysis (PCA), and canonical correspondence analysis (CCA). Field investigations were conducted in the growing season of 2014 using stratified random method in 22 homogeneous sampling units. In total, 75 plant species belonging to 52 genera and 19 families were identified. The most important families were Asteraceae and Papilionaceae, the most important genera were Astragalus, Cousinia, and Acanthophyllum, and the most important species were Artemisia aucheri and Artemisia sieberi. Plant species were classified into 10 groups using TWINSPAN. DCA was used to estimate the magnitude of changes in species composition along the first two ordination axes to provide gradient length estimations for PCA and CCA ordinations. The first three PCA axes and the first three CCA axes demonstrated similar cumulative percentage of variance, indicating that the environmental factors (selected by PCA) used in CCA ordination were acceptable for explaining the species composition and the distributions. CCA ordination showed that the first axis was closely related to elevation, slope, surface bare soil cover, surface litter cover, gravel proportion, organic matter, total nitrogen, CaCO3 content, and grazing intensity and that the second axis was closely related to sand proportion, silt proportion, clay proportion, and saturation percentage. Among these factors, elevation was the most effective factor to separate the plant groups and grazing was the major cause of rangeland degradation.

Niche-breadth of freshwater macrophytes occurring in tropical southern African rivers predicts species global latitudinal range

The study tested the hypothesis that measurement, using multivariate Principal Components Analysis (PCA), of the niche-breadth of river macrophyte species in southern tropical Africa, may predict their larger-scale biogeographical range. Two measures of niche-breadth were calculated for 44 riverine macrophyte species, from 20 families commonly occurring in Zambia, using an approach based on PCA ordination with 16 bio-physico-chemical input variables. These included altitude, stream order, stream flow, pH, conductivity and soluble reactive phosphate concentration (SRP). In the absence of additional chemical water quality data for Zambian rivers, invertebrate-based measures of general water quality were also used. These were benthic macroinvertebrate Average Score per Taxon (ASPT), and individual abundance of nine macroinvertebrate families with differing water quality tolerance, indicated by their Sensitivity Weightings within the Zambian Invertebrate Scoring System (ZISS). Macrophyte large-scale latitudinal range was derived from world geopositional records held by online databases, and additional records held by the authors. The two niche-breadth metrics divided the species into narrow-niche and intermediate/broad-niche categories, showing significant variation (from one or both of correlation and ANOVA test outcomes) in altitude, stream flow, conductivity, SRP, pH and ASPT, but not stream order. Macrophyte alpha-diversity (as a measure of number of individual niches co-existing per habitat) showed no significant relationship with individual species niche-breadth. Narrow-niche species included a higher proportion of Afrotropical endemics than did species with broader niche size. There were significant predictive relationships between macrophyte niche-breadth and latitudinal range of the target species at global and Afrotropical scales, but not for the Neotropics.

Impact of sample size on principal component analysis ordination of an environmental data set: effects on eigenstructure

Abstract In this study, we used bootstrap simulation of a real data set to investigate the impact of sample size (N = 20, 30, 40 and 50) on the eigenvalues and eigenvectors resulting from principal component analysis (PCA). For each sample size, 100 bootstrap samples were drawn from environmental data matrix pertaining to water quality variables (p = 22) of a small data set comprising of 55 samples (stations from where water samples were collected). Because in ecology and environmental sciences the data sets are invariably small owing to high cost of collection and analysis of samples, we restricted our study to relatively small sample sizes. We focused attention on comparison of first 6 eigenvectors and first 10 eigenvalues. Data sets were compared using agglomerative cluster analysis using Ward’s method that does not require any stringent distributional assumptions.

Patterns of AllocationCSRPlant Functional Types in Northern Europe

Morphological and physiological parameters of 76 vascular plant species typical for Northern Europe were analyzed using Grime’s classification.Cspecies (competitors) have high levels of canopy height, leaf dry weight, and maximal lateral spread.Rspecies (ruderal) have low leaf dry weight, longer flowering period, high rate of photosynthetic capacity and respiration, and high nitrogen content in the leaves. Stress-tolerant (S) species prevailing in habitats with limited resources are small and have low rate of photosynthetic activity and respiration. Principal component analysis (PCA) ordination showed a clear separation of species of different plant functional types according to their morphological and physiological parameters. The first PCA axis showed close relationship with the rate of respiration and photosynthetic activity and allowed us to differentiateSfromRspecies. The second PCA axis correlated with morphological parameters associated with the size of plants and allowed us to differentiateCspecies fromSandRspecies. Using PCA ordination, we developed a model that determines plant functional types in Northern Europe and analyzed plant functional types of several species that are not presented in Grime’s classification. The proposed model has higher accuracy (84%) compared to similar models designed for other climatic zones.

Mycorrhizas in Trifolium Repens – A Short Term High Experiment Approach

Abstract The paper aims to present the integrative potential of natural mycorrhization in short experiments. Mycorrhization parameters provide quantitative and qualitative indices of plant root development. Assessing the degree of dependence of plants to symbiotic association may represent an important step in estimating the strength and durability of a species in natural ecosystems. The degree of colonization is part of the methodology for estimating the volume explored by root symbiotic fungi, the value indicating the associative dependence. For values of the colonization degree below 10%, the association is casual and over 50% the association became mandatory. These values are due to a balanced frequencies and intensities. In general, differentiated fertilization and treatments acts to individualize the exploratory reaction of mycorrhizas. The strongest effects of the experimental variants are seen at the end of the growing season. Principal components analysis highlights the separation effect of fertilization and individualizes the treatments on graphs. Principal components analysis ordination of the colonization degree shows a normalization of mycorrhizal reaction to interaction fertilization x treatment and maximize the effect of experimental graduations. Zinc sulphate is the most restrictive treatment in combination with fertilization. Mineral or organo-mineral fertilization is beneficial for mulching at the vegetation peak and fungicides respond well to organo-mineral fertilization.

Weed seed bank diversity and community shift in a four-decade-old fertilization experiment in rice–rice system

The development of management practices that allow the prediction of timing and extent of weed emergence is essential for planning more effective weed control strategies as well as maintenance of biodiversity in agricultural systems. A better understanding of the seed bank could provide useful insights into the long-term effects of organic and chemical fertilization for maintaining diversity. The effects of organic and inorganic fertilization on weed seed bank composition, density and diversity were studied in the soil of a long-term fertilizer experiment established four decades ago in CRRI, Cuttack, India. Weed seed density was lowest for Paspalidium flavidum (22 individuals per m2) and highest for Ammania baccifera (11,616 individuals per m2) irrespective of the treatments. Highest weed seed density was observed in farm yard manure (FYM) treatment whereas, lowest was in NK treatment, which was 232% higher in FYM over NK treatment. Weed seedling emergence was higher in kharif flushes and lowest in rabi. Principal component analysis ordination indicated little similarity in the weed community composition particularly among NP, NPK and NPK+FYM, while application of N alone was quite distant. Weed species diversity was reduced significantly with application of inorganic N either applied with K or alone; therefore, lowest diversity and species richness was observed in NK treatment followed by N alone. The results of the study may contribute to the development of effective weed management strategies as well as maintenance of weed diversity which leads to transition from an herbicide-dependent cropping system to a more environmentally friendly cropping system.