Ordination Axes Research Articles

Diversity and ecological significance of modern fungal non-pollen palynomorphs in a European lowland forest ecosystem

Fungal non-pollen palynomorphs (fNPPs) are microscopic structures occurring in various sediments. In paleoecological studies, they can serve as reliable indicators of vegetation types, grazing activities, and human impact, enriching the interpretation of fossil data. This study explores the composition and taxonomic richness of fNPPs in 85 moss samples from a European lowland forest. We found rich fungal diversity, with 95 morphological types, predominantly saprotrophs, favoring specific substrates, like wood, decaying bark, herbaceous plant remains, litter, and freshwater habitats. Key taxa, such as type HdV-96A, and cf. Hypoxylon (EMA-24), were prevalent across different forest types, especially in deciduous forests. We identified two primary gradients of fNPP composition. The first axis delineated samples by taxonomic richness, Shannon index, and canopy openness, showing similarities among deciduous forests. The second axis ordered samples by the proportion of fNPPs, volume of stumps, coarse woody debris, and herbs pollen richness, highlighting their connections. Forest management intensity had minimal influence on fNPP composition, indicating consistent composition along both ordination axes. Forest type and herbs pollen richness, significantly affected the taxonomic richness and Shannon diversity of fNPPs. Deciduous forests exhibited higher fNPP richness, compared to coniferous forests, linked to increased herbs pollen richness. However, fNPPs decreased with increasing volume of stumps, coarse woody debris, and canopy openness, demonstrating the complexities of forest management’s influence on fungal diversity. This study pioneers fNPP investigation in an old-growth temperate forest ecosystem, emphasizing the interplay of forest characteristics, herbs diversity, and dead wood components in shaping their composition and richness. It also reveals differences in fNPP assemblages between deciduous and coniferous forests, underscoring the importance of forest type in shaping fungal diversity. These findings highlight the need for detailed studies on microhabitats, dead wood decomposition rates, and specific forest impacts to comprehensively understand forest ecosystem dynamics.

Determining the parameters of the functioning for a nonlinear ballistic system in a real external environment

Determining the parameters of the functioning for a nonlinear ballistic system in a real external environment

Измерение транспортабельности и стандартного геометрического отклонения транспортабельности радиоактивных аэрозолей с помощью каскадного импактора

An approach is proposed for the operational measurement of transportability and standard geometric deviation of transportability of radioactive aerosols in industrial conditions. The cascade impactor is preliminarily calibrated (graduated) in transportability units - this is a preliminary single measurement of transportability at each impactor cascade. After calibrating the impactor in transportability units, the transportability and standard geometric deviation of the transportability of radioactive aerosols can be repeatedly measured periodically and/or as needed. To do this, it is enough to measure the activity of the radionuclide at each impactor cascade using any available method. Based on measurements of radionuclide activity at each impactor cascade,an integral transportability distribution function is constructed for all cascades in percentage, then on paper. for lognormal probability graphs, the logarithms of the transportability of the cascade elements are plotted along the ordinate axis (but transportability values are indicated), and the total amount of the fraction activity is plotted along the abscissa axis. The obtained points determine the straight line f(S), the required transportability is S50, where f(S50) = 50%, the desired standard geometric deviation is bg = S84/S50, where f(S84) = 84%. A patent for the invention RU 2801822 C2 was issued for the presented means of measuring transportability and standard geometric deviation of transportability of radioactive aerosols.

Post-Contingency Loading Margin through Plane Change in the Continuation Power Flow

This paper introduces a parameterization technique to obtain complete P-V curves for electrical power systems under various conditions, including contingencies (N-1, N-1 severe, and N-2) as well as normal operating conditions N-0 (pre-contingency). The distinct feature of this methodology lies in the utilization of the new (θk, Vk) plane for constructing the P-V curve. In this new framework, the solution trajectory exhibits a linear characteristic in the vicinity of the maximum loading point (MLP), effectively mitigating any numerical challenges. Another crucial aspect is the point denoted as the center of the set of lines, point O (λ0, Vk0). This point can be adjusted along the ordinate axis, further enhancing the method’s ability to achieve a smoother ‘flat start’. The ‘flat start’ approach employed in the proposed methodology enables the determination of the loading margin for any system subjected to both simple and severe contingencies. Additionally, it facilitates the use of larger steps in acquiring complete P-V curves with a reduced number of iterations. A procedure presented is to not update the Jacobian matrix at each iteration but only when the system undergoes significant changes. This technique reduced the CPU Ratio by 29.74% in obtaining the P-V curve for all scenarios.

ON THE INTERACTION OF H[AuCl2] WITH 2-ETHYLIMIDAZOLE INTERACTION OF [AuCl2]- WITH 2-ETHYLIMIDAZOLE AT 278-318K

Using the potentiometric titration method, the process of complexation of gold (I) with 2-ethylimidazole was studied. Adding an organic ligand solution to the [AuCl2]-/Au system leads to a smooth decrease in the electrode potential (without any jumps). The nonlinearity of the dependence of E on –log[2EI] indicates the stepwise nature of complex formation between [AuCl2]- and 2-ethylimidazole. The general stability constants of successively formed complexes were determined in the temperature range 278-318K (at T=298K, logβ1=4.41±0.03; logβ2=10.81±0.02). An increase in temperature leads to the stability of the formed complexes. It has been shown that trivalent gold complexes are superior in stability to similar gold(I) complexes. The thermodynamic functions of the process of complex formation of gold (I) with 2-ethylimidazole were calculated using the temperature coefficient method. The value of enthalpy (∆Н0) was determined by the tangent of the slope of the direct dependence logβί0=f(1/T), the value of entropy (∆S0) by the segment cut off by this straight line on the ordinate axis, while the change in the isobaric-isothermal potential was calculated according to the equation ∆G0 =∆H0-T∆S0. It was revealed that the replacement of chloride ions with the ultraspherical molecule of 2-ethylimidazole is accompanied by a positive change in enthalpy. This experimental fact is associated with the difference in the binding energies of gold-chlorine (Au-Cl) and gold-2-ethylimidazole (Au-2-EI). A positive change in enthalpy makes a negative contribution to the spontaneous occurrence of complexation reactions. At the same time, the value of ∆S0 for the studied system has a positive value. In the [AuCl4]- –2-EI-H2O system, the number of particles participating in the complexation reaction remains unchanged. The positive change in entropy is most likely due to the release of the H2O molecule from the hydration shell of each of the reactants. A positive change in entropy promotes the spontaneous occurrence of complexation reactions in the studied system.

Temporal dynamics of steppe plant communities

Global climate change affects the conditions of ecosystems. However, the nature of changes induced by climatic factors remains unknown due to the complex nature of climatic transformations. The global trend of temperature increase is associated with an increase in precipitation and changes in its rhythm. The dynamics of plant communities under the influence of climate occurs against the background of natural successional phenomena. The aim of the study is to develop methodological approaches in order to identify aspects of vegetation variability that are caused by global climate change and give them an ecological interpretation. Geobotanical descriptions of vegetation in steppe ecosystems were carried out over the last 20 years. Exactly in this period dramatic climatic changes were observed, which allows to compare climatic and vegetation trends. For ecological interpretation the results of ordination of plant communities were explained with the help of phytoindication scales. Plant communities exhibit dynamics that are driven by endogenous and exogenous causes. These aspects of community dynamics were differentiated using the ordination procedure as different ordination axes. The axes that reflect endogenous dynamics were described using temporal variables. The axes that reflect exogenous dynamics were described using phytoindication scales. The phytoindication scales made it possible to assess the ecological directions of plant community transformation under the influence of global climate change. The transformation of the plant community under the influence of global climate change is inconsistent with the concepts of desertification. The revealed temporal patterns of the plant community have a complex and multidirectional trajectory. The plant community studied over the twenty-year investigation period exhibited a dynamic that is a superposition of two processes that are driven by the temperature and precipitation. The temperature trend is directional and reflects the tendency of global warming. This trend is accompanied by an increase in species richness and projective cover of the plant community. At the same time, thermophilicity and continentality of the community increase against the decrease of soil trophic status, acidity increase and soil carbonation decrease. Obviously, along with the mineralization of organic matter, the soil decarbonization can also be the cause of increased carbon dioxide emission into the atmosphere as a result of global warming. The trend, which is regulated by precipitation, is oscillatory. This trend changes the regime of moisture, light and cryoclimate of the plant community.

Asymptotic stability of the spectrum of a parametric family of homogenization problems associated with a perforated waveguide

AbstractIn this paper, we provide uniform bounds for convergence rates of the low frequencies of a parametric family of problems for the Laplace operator posed on a rectangular perforated domain of the plane of height H. The perforations are periodically placed along the ordinate axis at a distance between them, where ε is a parameter that converges toward zero. Another parameter η, the Floquet‐parameter, ranges in the interval . The boundary conditions are quasi‐periodicity conditions on the lateral sides of the rectangle and Neumann over the rest. We obtain precise bounds for convergence rates which are uniform on both parameters ε and η and strongly depend on H. As a model problem associated with a waveguide, one of the main difficulties in our analysis comes near the nodes of the limit dispersion curves.

Влияние добавок галлия на анодное поведение проводникового алюминиевого сплава E-AlMgSi («алдрей») в среде электролита NaCl

The work presents the results of the study of the anodic behavior of aluminum alloy E-AlMgSi (aldrey) with gallium, in the medium of 0.03; 0.3 и 3.0% NaCl electrolyte. The corrosion-electrochemical study of alloys was carried out using the potentiostatic method. It was shown that doping E-AlMgSi (aldrey) with gallium increased its corrosion resistance by 20%. The main electrochemical potentials of the alloys when doping with gallium are shifted to the positive range of values, and at the concentration of sodium chloride to the negative values of the ordinate axis.

Processing algorithm of weekly records of the Roztochia landscape-geophysical station thermograph М-16АН as a response source of air temperature data

Formulation of the problem. During the database processing of the Roztochia landscape-geophysical station (RLGS), located in the village of Bryukhovychi, Lviv, an air temperature data gap for 1990–1991 was found. The task of the research was to find those sources about air temperature at RLGS, which would allow us to fill in the gaps during the night hours when, unfortunately, observers did not make measurements. Problems of further research. In comparison with the method adopted in Ukraine for processing weekly thermograph tapes, in this study, it is proposed to correct the air temperature value during their processing, compensating for accelerated or slowed rotation of the weekly thermograph drum. It is suggested to use only those dry bulb measurements carried out on days with cloudy or rainy weather. The purpose. The main goal was to find an algorithm for processing weekly thermograph tapes under the conditions of a partial absence of temperature measurements using a dry thermometer by an observer to fill in the gaps regarding night air temperature data. Research methods. The air temperature values falling during the measurement period were read from the thermograph tapes, and an electronic table was formed. The temperature values (difference estimation) were compared with the corresponding ones recorded in the "Books" of KM-1. At the same time, it was necessary to make two new corrections. The first correction will be made along the ordinate axis, changing the value of the temperature recorded by the thermograph compared to the values of the temperature measured by the dry thermometer. The second correction was made along the abscissa axis, compensating for the drum's slowed down or accelerated rotation. Presentation of the main research material. A brief description of the proposed algorithm for thermograph tape processing is as follows. In the spreadsheet, in separate columns, we record the temperature values during the observation periods: a) by dry thermometer and b) by thermograph at the points corresponding to the observation periods. Subtracting columns (a) and (b) values, we determine those dry bulb temperature values suitable for calculating corrections. We reject too significant differences that occur during rapid temperature changes. Next, we look for points on the thermograph tape that serve as time benchmarks (the starting and ending points of the temperature curve and the places where the observer draws vertical lines). These temperature values will form column (c). It will additionally include the temperature values obtained by reading the temperature from the tape for rainy and/or overcast days for points whose localization is corrected for time. The difference between column (a) and column (c) will give the temperature correction for several observation periods on each weekly strip taken separately. The last step is the linear interpolation of temperature corrections between neighbouring points of intermediate observation periods. Practical value. The proposed algorithm may help eliminate gaps in temperature data at other observation points, where the thermograph served as a backup device for recording air temperature. Research results. The measurements that fall on rainy and overcast weather are best suited for calculating thermograph corrections when air temperature changes slow down. It is necessary to identify benchmark points of time fixation, to which the observer must add the moments of putting on and removing the tape from the drum.

Influences of adjacent suburbia, fire regimes and vegetation on the mammals of a peri-urban reserve

Urban development is thought to negatively affect most native mammals. Here we assess whether adjacent suburbia, fire regime and vegetation influence the activity of mammal species in a reserve in Hobart, Tasmania, Australia. We used multiple regression to analyse the relationship between distance from houses, fire history, vegetation structure and floristics, and mammal activity, derived from camera visits and signs. Animal diggings and visits by long-nosed potoroos, southern brown bandicoots and cats were greater close to houses, while visits by red-necked wallabies, rufous-bellied pademelons, brushtail possums and short-beaked echidnas were not. The structure of the vegetation, particularly related to shelter, was important in many models. Many models also included floristic ordination axes that reflected drainage, fire regime and distance from high-density housing. Positive relationships between the introduced predatory cat and some of its potential native prey animals may reflect the influences of close proximity to suburbia, such as elevated domestic mesopredator populations, and elevated resource availability in domestic gardens. Our results suggest that urban areas can have a valuable role in nature conservation, despite, or because of, their effects on remnant native ecosystems.

КОНЦЕНТРАЦИЯ ИОНОВ КАЛИЯ В СПЕРМЕ МОЖЕТ СЧИТАТЬСЯ ДЕТЕРМИНАНТОЙ КЛИНИЧЕСКОЙ ЭФФЕКТИВНОСТИ МАСЛА СЕМЯН ТЫКВЫ У ПАЦИЕНТОВ С ХРОНИЧЕСКИМ ПРОСТАТИТОМ 3Б

Background. For objective assessment of the functional status of prostatic tissue, the «Kalium Parameter of Laboratory analysis, Evaluating in Ejaculate (KAPLEE)» was offered. KAPLEE is the concentration of K+ ions, measuring with the help of potentiometry in 42 ml of water solution, which contains 1 ml of ejaculate, 39 ml of distilled water and 2 ml of special buffer solution. The aim: to check the hypothesis that the deviation of KAPLEE from the normal range towards reduction or towards increase is the determinant of less efficacy of pumpkin seed oil (PSO) in patients with chronic prostatitis 3B (CP3B). Materials and methods: In trial 51 patients with the diagnosis of CP3B, who received PSO 5400 mg a day (4 capsules 3 times a day) for 30 days as monotherapy, took part. The study included 2 stages. During first stage each patient evaluated the efficacy of this pharmacotherapy in his case; it varied from 1 point (absolute non-efficacy) to 5 points (absolute efficacy). Then each patient ejaculated into container, and the concentration of KAPLEE was measured. Thus, the data of each patient were placed in two-axial system of coordinates: axis of abscisses was the concentration of KAPLEE, axis of ordinates was the mark of efficacy. Then the cluster analysis of these data was made. Results and conclusion. Concentration of potassium ions in the sperm can be considered a determinant of clinical effectiveness of pumpkin seed oil in patients with chronic prostatitis.

Decomposing trends in bird populations: Climate, life histories and habitat affect different aspects of population change

AbstractAimDespite the complexity of population dynamics, most studies concerning current changes in bird populations reduce the trajectory of population change to a linear trend. This may hide more complex patterns reflecting responses of bird populations to changing anthropogenic pressures. Here, we address this complexity by means of multivariate analysis and attribute different components of bird population dynamics to different potential drivers.LocationCzech Republic.MethodsWe used data on population trajectories (1982–2019) of 111 common breeding bird species, decomposed them into independent components by means of the principal component analysis (PCA), and related these components to multiple potential drivers comprising climate, land use change and species' life histories.ResultsThe first two ordination axes explained substantial proportion of variability of population dynamics (42.0 and 12.5% of variation in PC1 and PC2 respectively). The first axis captured linear population trend. Species with increasing populations were characterized mostly by long lifespan and warmer climatic niches. The effect of habitat was less pronounced but still significant, with negative trends being typical for farmland birds, while positive trends characterized birds of deciduous forests. The second axis captured the contrast between hump‐shaped and U‐shaped population trajectories and was even more strongly associated with species traits. Species migrating longer distances and species with narrower temperature niches revealed hump‐shaped population trends, so that their populations mostly increased before 2000 and then declined. These patterns are supported by the trends of total abundances of respective ecological groups.Main ConclusionAlthough habitat transformation apparently drives population trajectories in some species groups, climate change and associated species traits represent crucial drivers of complex population dynamics of central European birds. Decomposing population dynamics into separate components brings unique insights into non‐trivial patterns of population change and their drivers, and may potentially indicate changes in the regime of anthropogenic effects on biodiversity.

Floristic diversity, composition and dominance across Amazonian forest types respond differently to latitude

AbstractAimThe latitudinal biodiversity gradient is considered a first‐order biogeographical pattern for most taxonomic groups. Latitudinal variation in plant diversity is not always consistent, and this could be related to the particular characteristics of different forest types. In this study, we compare latitudinal changes in floristic diversity (alpha diversity), composition (beta diversity) and dominance across different tropical forest types: floodplain, terra firme and submontane forests.LocationWestern Amazonia (Ecuador, Peru and Bolivia).TaxonWoody plants.MethodsWe inventoried 1978 species and 31,203 individuals of vascular plants with a diameter at breast height ≥ 2.5 cm in 118 0.1‐ha plots over an 1800 km latitudinal gradient in three different forest types. The relationships between alpha diversity, latitude and forest type were analysed using generalised linear mixed models. Semi‐parametric permutational multivariate analysis of variance was used to investigate the effects of latitude and forest type on beta diversity. Dominant species abundances were correlated with non‐metric multidimensional scaling ordination axes to reflect their contributions in shaping changes in beta diversity.ResultsAlpha diversity increased towards equatorial latitudes in terra firme and submontane forests but remained relatively constant in floodplains. Beta diversity of all forest types changed with latitude, although less clearly in floodplains. Also, in floodplain forests, there were fewer dominant species contributing to beta diversity and more species homogeneous along the gradient.Main ConclusionsLatitudinal diversity patterns are manifested in alpha and beta diversity since latitude summarizes climatic and edaphic changes. However, we found different responses of each forest type. In floodplain forests, inundation regime is a stronger predictor than latitude, limiting floristic diversity and composition. Changes in dominant species abundance over gradients explained species composition, but floodplain forests harboured more homogeneous dominant species than well drained forests. It is key to study environmental trends and habitat characteristics of each forest type to understand their species diversity and dominance patterns.

Filtration velocity under roller squeezing

Analytical dependencies are determined that describe the patterns of change in filtration rates in the squeezing area. It was established that the fluid filtration rate along the abscissa axis at the boundaries of the compression zone is zero, and inside the zone, it takes negative values. It was found that the fluid filtration rates along the ordinate axis are zero at the beginning of the compression zone; they increase to a maximum at a point lying on the line of centers, and in the zone of strain restoration, they depend on the angle that determines the position of the point where the fluid changes direction.

Technological basis of rotation of body with polygon

Front-end plows are promising and carry out smooth plowing. A significant disadvantage of the front plow is that the housings do not completely rotate the layers within their own furrow and have a large traction resistance since they work in conditions of blocked cutting. The study aims to substantiate the technology of turnover of a polygonal formation in conditions of non-blocked cutting. The basic principles and methods of classical mechanics, mathematical analysis, and statistics were used in this study. The parameters of the polygonal formation formed by the angle beam and the body of the plow have been studied. Analytical dependences for determining the coordinate of the center of gravity of the formation and the displacement of its center of gravity along the ordinate axis are obtained. It was found that the displacement of the center of gravity of the formation along the ordinate with a formation width of 45-52.5 cm and a gripping width of the angle of 4-10 cm is 4-10 cm.

Long-Term Monitoring of Vegetation Cover on Drained Mires of South Karelia (Mesotrophic Herb–Sphagnum Mire)

With the help of gradient analysis and Ellenberg eco-scales, factors of differentiation of vegetation cover (moisture, illumination, soil acidity, and soil richness in mineral nitrogen) were revealed. Using nonmetric scaling, an ordination diagram of the distribution of geobotanical descriptions was created for 50 years of research (from 1971 to 2021). Correlation of ordination axes and ecological factors was carried out. On the ordination diagram and according to the results of cluster analysis, geobotanical descriptions form three distinct groups corresponding to certain time periods. Changes in the species composition in plant communities are caused by changes in illumination, moisture, and trophicity. Under the influence of drainage and successions of the vegetation cover for 50 years, on the site of a mesotrophic hummock-flark herb sphagnum mire, represented by mesotrophic hydrohygrophilous mire species, an oligotrophic hummock lawn dwarf-sphagnum pine forest was formed, formed by oligotrophic, mesohygrophilic forest-mie species.

Tree species on environmental gradients in subtropical forest of northwest Belize, in the Maya Lowlands

We studied species composition and spatial distributions of tree species, and the underlying topography and soil, in subtropical forests of northwest Belize, a region in the Maya Lowlands. Our goal was to learn how much the spatial distributions of species vary and are predictable over the landscape. The study was done in old-growth, subtropical moist forest on limestone-derived topography and soil. We identified to species all trees ≥10 cm DBH in 209 400-m2 plots. For each plot, we characterized topographic setting and analyzed soil nutrients and texture. We recorded 3,984 individual trees of ∼140 tree species and used the 3,775 individuals of the 69 species occurring in ≥5 plots in multivariate analyses, including Nonmetric Multidimensional Scaling (NMS). NMS showed that 73% of the variation in species composition per plot was associated with the first three ordination axes. Sixteen out of the 34 quantitative variables we measured were correlated at R 2 > 10% with the axes. Of the categorical variables, Topographic Class was strongly associated with species composition, and USDA Texture Class less so. Of the 69 focal tree species, the abundances of 21 were correlated at R 2 > 10% with one or more axes of the NMS ordination. Importantly, these 21 species accounted for 68% of all individual trees sampled in the 209 plots. Twenty-three species were indicators of particular topographic and soil classes. We conclude that patterns of tree species distribution are strongly and predictably associated with different topographic and soil conditions in this landscape. In the past, the ancient Maya could have used this type of predictable plant–soil relationship to optimize their agriculture. In the future, our results are a basis for predicting local shifts in tree species distributions due to climate change.

Vegetation and biotopes of the regional botanical natural monument «Kashtak Pine Forest» (Sosnovskiy District of Chelyabinsk Oblast)

The vegetation and biotopes of the regional botanical natural monument Kashtak Pine Forest have been characterized in this paper. By multivariate statistics and a dominant approach 13 pine and birch-pine plant associations have been identified. But in most cases the associations are detected by dominance or co-dominance of Fragaria vesca L. in the herbage in spite of high biodiversity. The difference of associations is identified by shrub species dominance mainly. The biotopes of the regional botanical natural monument Kashtak Pine Forest are not characterized by principal abiotic factors of high variation while the differences are determined by coenotic factors. The classification of Kashtak Pine Forest biotopes is identified by soil acidity and soil nitrogen regimes in the first place. For Kashtak Pine Forest three ordination axes have been detected: 1) boreal pine forests of Boreal zone, 2) temperate pine and birch-pine forests of Temperate Forest and Forest-Steppe zones and 3) axe of soil moistening and cryoregime. Three coenotic series have also been detected: hydrosere of Fragaria vesca associations and two trophoseries of boreal pine forests of Boreal zone. These series form an integrated biotopical sere and succession of South-Urals pine forests from temperate forest-steppe pine forests to boreal pine forests of Boreal zone.

Assessing Metallic Pollution Using Taxonomic Diversity of Offshore Meiobenthic Copepods

The Gulf of Gabès, located on the south-east Tunisian coast, is an important maritime area, with great influence on the local economy and human welfare. The aim of the current study was to assess the response of meiobenthic copepod populations from this gulf to anthropogenic disturbances. Nine sampling sites, situated along the shores of the gulf were surveyed seasonally from winter of 2004 to autumn of 2005. Interestingly, this biotope has one of the highest semi-diurnal tides in the Mediterranean Sea. Despite the fact that the data being presented here are not that new, such a high maximum amplitude of tides reaching 2 m makes any information available on animals with diurnal dispersal cycles such as copepods extremely precious. Furthermore, the lack of knowledge on these crustaceans is obvious and lags behind that of numerous other meiobenthic taxa and planktonic calanoids. Actually, most publications do not reach the species level and are limited to determining densities. This is mainly due to the modest size of harpacticoids, and the lack of qualified taxonomic experts and global taxonomic databases. Sediment samples were analyzed for fluorine, carbohydrates and trace metals (i.e., Fe, Zn and Cd) content. A pollution index, based on the eigenvalues of the main ordination axis of a Principal Component Analysis, was applied. The highest values of chemicals were detected at the sites situated near an industrial complex, along with significant variations among seasons. The copepod community comprised 38 species, including five species new to science. Species richness, density and biomass of copepod communities varied among sites and seasons. These community-based indices were also analyzed separately for each season with conditional autoregressive models, revealing a significant negative response with the level of pollution. However, the results of partial Mantel tests showed positive correlations between species richness and pollution level, after controlling for the effect of geographic proximity in-between pairs of sites (winter: r = 0.927, p < 0.0001; spring: r = 0.935, p < 0.0001; summer: r = 0.918, p < 0.0001; autumn: r = 0.937, p < 0.0001). The overall pattern was that nearby sites were characterized by similar pollution levels and inhabited by similar species of copepods. Moreover, the copepod communities were significantly influenced by pollutants, mainly by trace metals. The results of the current survey emphasize the usefulness of meiobenthic copepods in biomonitoring programs not only for the gulf of Gabès, but also for other coastal areas from the Mediterranean Sea region.

Southern Carpathian ultramafic grasslands within the central-southeast European context: syntaxonomic classification and overall eco-coenotic patterns

BackgroundPrevious investigations carried out in ultramafic habitats emphasized the greater importance of site conditions over soil toxic metal content for vegetation composition. Very little is known about the floristic structure of the Southern Carpathian ultramafic grasslands and there is no information on the local environmental drivers of their composition and coenotic features. Here, we aim to fill these knowledge gaps by referring to similar phytocoenoses described in the Balkan Peninsula and central Europe. In particular, we searched for: (i) floristic and ecological patterns supporting the classification and taxonomic assignment of these grasslands, and (ii) simple relationships between serpentine vegetation characteristics and its physiographic environment. A total of 120 phytosociological relevés, of which 52 performed in the Southern Carpathians, were analysed through cluster, ordination and regression procedures.ResultsDespite some floristic similarities with their Balkan counterparts, the Southern Carpathian ultramafic grasslands were clustered into four distinct groups, which were assigned to as many new syntaxa: Plantago serpentinae–Armerietum halleri, Asplenio serpentini–Achnatheretum calamagrostis, Minuartio frutescentis–Plantaginetum holostei and Sileno saxifragae–Plantaginetum holostei. The latter was best individualised through the occurrence of several Carpathian endemic taxa. The first two ordination axes were significantly related with the terrain slope/presence of xerophilous species and respectively, with site elevation/presence of calcifugous species. The total plant cover showed a unimodal relationship with respect to site elevation. While controlling for the effect of the sampled area, species richness showed a unimodal response to both elevation and slope of the terrain, although their effects were not singular.ConclusionsThe syntaxonomic distinctiveness of the Southern Carpathian ultramafic grasslands is mainly supported by their overall species composition rather than regional differential species. The main limiting factors driving the composition, cover and species richness of all studied ultramafic grasslands are the water deficit at low elevation and on steep slopes, and the low soil fertility at higher elevations. Our results confirm the previous findings according to which physiographic conditions and, to a lesser extent, soil base nutrients are more important than heavy metal concentrations in structuring the ultramafic vegetation.