scholarly journals Diversity, ecology and distribution of benthic diatoms in thermo-mineral springs in Auvergne (France) and Sardinia (Italy)

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e7238 ◽  
Author(s):  
Giuseppina G. Lai ◽  
Aude Beauger ◽  
Carlos E. Wetzel ◽  
Bachisio M. Padedda ◽  
Olivier Voldoire ◽  
...  
Keyword(s):  
Environmental Variables ◽  
Multivariate Analyses ◽  
Climatic Factors ◽  
Geographic Region ◽  
Species Level ◽  
Diatom Assemblages ◽  
Mineral Springs ◽  
Diatom Flora ◽  
Crucial Step ◽  
Fine Sediments

This study investigated and compared the diatom flora from thermo-mineral springs in Auvergne (France) and Sardinia (Italy). Samples were collected from rock/cobbles and fine sediments in 16 springs between January 2015 and March 2017. A total of 207 taxa (59 genera) were found. Multivariate analyses revealed significant differences in species composition and abundance among diatom assemblages both within each geographic region and between Auvergne and Sardinia (global R = 0.516; p = 0.002), suggesting the importance of local and climatic factors in species distribution. Based on abundance and common occurrence in multiple sites, some taxa can be considered more representative of springs in each region: Crenotia thermalis for Auvergne and Lemnicola exigua, Nitzschia amphibia, N. inconspicua and Rhopalodia operculata for Sardinia. pH, conductivity and HCO3− were the most significant environmental variables for diatom assemblages. Our results highlight the high heterogeneity of these spring systems. Future taxonomic insights can be useful to define the identity of some abundant and dominant taxa not identified at the species level in this study. Their identification is a crucial step for a more precise ecological characterization and comparison of these peculiar spring systems.

Holocene diatom assemblages from Dunderbukhta sediments, West Svalbard

2019 ◽  
pp. 242-245
Author(s):  
Ksenya V. Poleshchuk ◽  
Zinaida V. Pushina ◽  
Sergey R. Verkulich
Keyword(s):  
Environmental Changes ◽  
Ecological Groups ◽  
Diatom Assemblages ◽  
Diatom Analysis ◽  
Diatom Flora ◽  
Sediment Samples ◽  
Ecological Zones ◽  
Middle Holocene ◽  
Temperature Trends

The diatom analysis results of sediment samples from Dunderbukta area (Wedel Jarlsberg Land, West Svalbard) are presented in this paper. The diatom flora consists of four ecological groups, which ratio indicates three ecological zones. These zones show environmental changes of the area in early–middle Holocene that is demonstrating periods of regression and temperature trends.

Environmental factors including management practices as correlates of weed community composition in spring seeded crops

1992 ◽  
Vol 70 (10) ◽  
pp. 1931-1939 ◽  
Author(s):  
M. R. T. Dale ◽  
A. G. Thomas ◽  
E. A. John
Keyword(s):  
Community Composition ◽  
Correspondence Analysis ◽  
Canonical Correspondence Analysis ◽  
Environmental Variables ◽  
Management Practices ◽  
Geographic Region ◽  
Climatic Conditions ◽  
Weed Species ◽  
Weed Communities ◽  
Seed Crops

The relationship between the weed communities and environmental variables such as soil, crop, and management was investigated in two provinces of Canada. The frequencies of weed species were recorded in cereal and oilseed fields in Saskatchewan (2244 fields over 4 years) and Manitoba (864 fields over 3 years), Canada. Information on some of the physical characteristics of the fields and on the management practices imposed on them was also collected, in part by questionnaire. The two kinds of data were ordinated together using canonical correspondence analysis to assess the relationships between the species and the environmental variables. In the Saskatchewan data, there was a clear and consistent separation of the species into groups along an axis correlated with soil zone and the associated climatic gradient. In the Manitoba data, the same groups of species did not separate as clearly or as consistently, although geographic region was a major determinant of the weed communities. The greater variability may be due to the fact that the gradient of soil types is much more restricted in Manitoba and not as closely correlated with climatic conditions. In both provinces, culture practices were less important as correlates of the weed community composition than soil type or, to a certain extent, the previous crop. Key words: canonical correspondence analysis, cereal crops, oil seed crops.

scholarly journals Biodiversity of bulbous and tuberous geophytes from the El Kala National Park (North-Eastern Algeria): checklist, vulnerability and conservation

2019 ◽  
pp. 25-38
Author(s):  
Besma Dechir ◽  
Atef Chouikh ◽  
Tarek Hamel ◽  
Nawel Nadia Azizi ◽  
Nawel Ganaoui ◽  
...  
Keyword(s):  
New Species ◽  
Environmental Variables ◽  
National Park ◽  
Multivariate Analyses ◽  
North Eastern ◽  
Floristic Analysis ◽  
The Subject ◽  
Eastern Algeria ◽  
A New Species

Treinta estaciones en el Parque Nacional El Kala (Noreste de Argelia) fueron objeto de un inventario florístico que se centró en el estudio de la ecología de geófitos bulbosos y tuberosos. La flora se caracteriza por una alta proporción de taxones raros y/o endémicos, entre ellos, 6 especies son endemismos algero-tunecinos pertenecientes a la familia Orchidaceae. En este trabajo, se da a conocer la presencia de una nueva especie para la flora argelina, Ophrys fusca subsp. lupercalis. Los análisis multivariantes revelaron, ciertas variables ambientales que determinan la distribución de los geófitos. Los lugares de interés son particularmente sensibles a las amenazas, particularmente las de origen antrópico. Thirty stations at the El Kala National Park (North Eastern Algeria) were the subject of a floristic focused on the study of the ecology of bulbous and tuberous geophytes. The floristic analysis was used to draw up a checklist of 67 species belonging to 36 genera and 14 families, among of which 19 species a high proportion of rare and/or endemic taxa; among them six signed taxa are endemic to algerian-tunisian mainly represented by family of Orchidaceae. In this work, we recorded the presence of a new species for the Algerian flora which is Ophrys fusca subsp. lupercalis. Multivariate analyses revealed certain environmental variables determining the distribution of geophytes. The visited sites show an alarming vulnerability and subject to threats, particularly anthropogenic ones.

scholarly journals The structure and diversity of freshwater diatom assemblages from Franz Josef Land Archipelago: a northern outpost for freshwater diatoms

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e1705 ◽  
Author(s):  
Sergi Pla-Rabés ◽  
Paul B. Hamilton ◽  
Enric Ballesteros ◽  
Maria Gavrilo ◽  
Alan M. Friedlander ◽  
...  
Keyword(s):  
Seasonal Changes ◽  
Ph Gradient ◽  
Diatom Assemblages ◽  
Diatom Flora ◽  
Human Footprint ◽  
Franz Josef Land ◽  
Freshwater Diatoms ◽  
Arctic Conditions ◽  
Cell Densities ◽  
Freshwater Diatom

We examined diatom assemblages from 18 stream and pond samples in the Franz Josef Land Archipelago (FJL), the most northern land of Eurasia. More than 216 taxa were observed, revealing a rich circumpolar diatom flora, including many undescribed taxa. Widely distributed taxa were the most abundant by cell densities, while circumpolar taxa were the most species rich. Stream and pond habitats hosted different assemblages, and varied along a pH gradient.Diatoma tenuiswas the most abundant and ubiquitous taxon. However, several circumpolar taxa such asChamaepinnularia gandrupii, Cymbella botellus, Psammothidiumsp. andHumidophila laevissimawere also found in relatively high abundances. Aerophilic taxa were an important component of FJL diatom assemblages (Humidophilaspp.,Caloneisspp. andPinnulariaspp.), reflecting the large and extreme seasonal changes in Arctic conditions. We predict a decrease in the abundance of circumpolar taxa, an increase in local (α-) freshwater diatom diversity, but a decrease in regional diversity (circumpolar homogenization) as a result of current warming trends and to a lesser extent the increasing human footprint in the region.

Using Diatoms as Ecological and Paleoecological Indicators in Riverine Environments

2007 ◽  
Vol 13 ◽  
pp. 121-130
Author(s):  
Jeffery R. Stone
Keyword(s):  
Spatial Distribution ◽  
Environmental Changes ◽  
Climatic Factors ◽  
Diatom Assemblages ◽  
Meandering River ◽  
Rates Of Change ◽  
Terminal Lakes ◽  
Riverine Systems ◽  
The Impact ◽  
Selection Of

Fossil diatom assemblages are useful for reconstructing past environmental changes in riverine systems. However, few studies have attempted to utilize paleolimnological techniques in these settings. Analysis of sediments from riverine environments can provide key information predating the impact of human development, which cannot be acquired by other means. Paleolimnological techniques can be used to determine the natural variability in these systems and to estimate the magnitude and rates of change that the environment may have undergone as a result of anthropogenic or climatic factors, and to provide realistic goals for management of negatively-impacted systems.Reconstructing past riverine settings requires an understanding of the factors that control the spatial distribution of diatoms in riverine settings; this paper discusses the impact of resources, stressors, and disturbance events, which are the primary controls on the distribution of benthic diatoms in modern riverine environments. A selection of case studies that utilize paleolimnological techniques to infer past stream hydrology are also discussed; these examples encompass the use of fossil diatom assemblages from sediments recovered from lowland floodplain and meandering river systems, estuarine environments, fluvial lakes, arctic deltaic environments, and terminal lakes.

scholarly journals Diatom Biodiversity in Karst Springs of Mediterranean Geographic Areas with Contrasting Characteristics: Islands vs Mainland

Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2602 ◽  
Author(s):  
Giuseppina G. Lai ◽  
Sara Burato ◽  
Bachisio M. Padedda ◽  
Raffaella Zorza ◽  
Elisabetta Pizzul ◽  
...  
Keyword(s):  
Anthropogenic Impact ◽  
Multivariate Analyses ◽  
Winter Season ◽  
Global Scale ◽  
Diatom Assemblages ◽  
Karst Springs ◽  
Karst Ecosystems ◽  
Structural Indices ◽  
Epilithic Diatom

Karst ecosystems are considered as priority environments for the protection of biodiversity on a global scale. This study provides a first comparative analysis of epilithic diatom flora from karst springs in two Mediterranean geographic areas (Spain and Italy) with contrasting characteristics (islands vs mainland). We investigated twenty-three springs with different anthropogenic impact levels once in the winter season between 2007 and 2017 (N = 23). A total of 176 diatom taxa (56 genera) were found of which 101 (44 genera) were observed in single sites. A general good biotic integrity was revealed by structural indices (species richness, diversity and evenness). However, crenophilous species were generally present and abundant in less impacted springs. Comparing islands and mainland, significant differences were found in species composition and diversity (H’) based on multivariate analyses (global R = 0.610; p = 0.001) and t-test (t = 2.304; p = 0.031). Discharge and Cl− were the most significant variables in determining diatom assemblages. Our results confirm the role of springs as multiple ecotones and refuges for rare species and suggest that the geographic insularity may be an important factor in maintaining diatom biodiversity.

The geography and climatology of aerosols

2003 ◽  
Vol 27 (4) ◽  
pp. 502-547 ◽  
Author(s):  
Helen C. Power
Keyword(s):  
Spatial Variability ◽  
Climatic Factors ◽  
Polar Front ◽  
Geographic Region ◽  
Climate System ◽  
Radiative Properties ◽  
Aerosol Emission ◽  
Temporal And Spatial Variability ◽  
Temporal And Spatial ◽  
Total Column

Aerosols affect climate by scattering and absorbing radiation and by modifying the physical and radiative properties of clouds. Despite their importance in the climate system, the temporal and spatial variability of aerosols is not well understood. This paper briefly describes the nature of aerosols, their influence on the climate system and methods for quantifying atmospheric turbidity, which is the total column amount of aerosol. The main focus of the paper is a review of turbidity research that serves to document how and why aerosols vary over time and space. This analysis reveals that temporal and spatial variability in aerosol emissions is superimposed by temporal and/or spatial variability in meteorological and climatic factors. These factors include variability in wind speed, humidity, stability, insolation, frontal and cyclonic activity, the position of the Intertropical Convergence Zone and the polar front, rates of precipitation and convection, and the source regions of air masses. This interaction between aerosol emission characteristics and atmospheric processes is manifested in distinct trends in total column aerosol -described herein by geographic region - at a variety of spatial and temporal scales.

scholarly journals Fenologia de Blechnum acutum (Desv.) Mett. (Blechnaceae) em Floresta Atlântica Subtropical (Phenology of Blechnum acutum (Desv.) Mett. (Blechnaceae) in Atlantic Subtropical Forest)

2016 ◽  
Vol 9 (6) ◽  
pp. 1644 ◽  
Author(s):  
Thábia Ottília Hofstetter Padoin ◽  
Andressa Müller ◽  
Jairo Lizandro Schmitt
Keyword(s):  
Atlantic Forest ◽  
Environmental Variables ◽  
Climatic Factors ◽  
Seasonal Pattern ◽  
Subtropical Forest ◽  
Circular Statistics ◽  
Activity Period ◽  
Determining Factors ◽  
The World ◽  
Reproductive Events

O clima de uma área é um dos fatores determinantes da dinâmica da vegetação e a fenologia estuda a ocorrência dos eventos vegetativos e reprodutivos das plantas desencadeados principalmente pela precipitação, temperatura e fotoperíodo. Os estudos fenológicos com samambaias, no mundo, aumentaram nas últimas décadas, porém os seus resultados são geralmente descritivos e restritos a poucos locais e a poucas espécies. Foram determinados o padrão e a sazonalidade das fenofases de Blechnum acutum, em Floresta Atlântica subtropical, relacionando-as com os fatores climáticos, a partir do monitoramento de 20 indivíduos, durante 18 meses. Para verificar a sazonalidade das fenofases foi utilizada a estatística circular. Blechnum acutum apresentou maior intensidade da renovação foliar em janeiro (38%), com maior período de atividade entre janeiro e abril de 2014. A formação de esporângios foi a fenofase que demonstrou o padrão sazonal mais evidente e ocorreu com maior intensidade e atividade em outubro de 2014 (25%). A senescência foliar manifestou maior intensidade em fevereiro de 2014 (23%), com 80% dos indivíduos encontrando-se nesta fenofase, em março de 2015. Os padrões fenológicos não demonstraram a mesma continuidade e regularidade em decorrência principalmente da falta de homogeneidade na manifestação da renovação e senescência das folhas pelos indivíduos na população. Os ritmos fenológicos de B. acutum também não foram igualmente influenciados pelas variáveis ambientais analisadas, sendo que a renovação foliar foi a única fenofase relacionada com temperatura e fotoperíodo.     A B S T R A C T The climate of an area is one of the determining factors of the vegetation’s dynamics and phenology studies. The occurrence of vegetative and reproductive events of plants mainly triggered by rainfall, temperature and photoperiod. The phenological studies with ferns in the world have increased in recent decades, but the results are usually descriptive and restricted to few places and few species. It was determined the pattern and seasonality of phenophases of Blechnum acutum in subtropical Atlantic Forest, relating them to the climatic factors, from monitoring 20 individuals for 18 months. To check the seasonality of phenophases the circular statistics were used. Blechnum acutum showed greater intensity of foliar renovation in January (38%), with higher activity period between January and April 2014. The sporangia formation was the phenophase that showed the most obvious seasonal pattern and was more intense and activity in October 2014 (25%). The leaf senescence showed greater intensity in February 2014 (23%), with 80% of individuals meeting in this phenophase in March 2015. The phenological patterns did not show the same continuity and regularity mainly due to the lack of homogeneity in the manifestation renewal and senescence of leaves by individuals in the population. The phenological rhythms of B. acutum were not also influenced by environmental variables, and the leaf renewal was the only phenophase related to temperature and photoperiod. Keywords: climate, photoperiod, sazonality, phenophase, fern.[1]                                                            

scholarly journals Climatic Factors, Reproductive Success and Population Dynamics in the Montane Vole, Microtus montanus

1991 ◽  
Vol 15 ◽  
pp. 162-164
Author(s):  
Aelita Pinter
Keyword(s):  
Population Dynamics ◽  
Reproductive Success ◽  
Population Density ◽  
Environmental Variables ◽  
Climatic Factors ◽  
Small Rodents ◽  
Term Study ◽  
Microtus Montanus ◽  
Long Term Study

Multiannual fluctuations in population density ("cycles") of small rodents have been known since antiquity (Elton 1942). Numerous hypotheses have been proposed to explain this phenomenon (for reviews see Finerty 1980, Taitt and Krebs 1985). However, none of these hypotheses, alone or in combination, have been able to explain the causality of cycles. The objectives of this long-term study are to determine whether environmental variables, possibly acting through reproductive responses, contribute to the multiannual fluctuations of the montane vole, Microtus montanus.

scholarly journals Climatic Factors, Reproductive Success and Population Dynamics in the Montane Vole, Microtus montanus

1987 ◽  
Vol 11 ◽  
pp. 103-105
Author(s):  
Aelita Pinter
Keyword(s):  
Population Dynamics ◽  
Reproductive Success ◽  
Population Density ◽  
Environmental Variables ◽  
Climatic Factors ◽  
Small Rodents ◽  
Term Study ◽  
Microtus Montanus ◽  
Long Term Study

Multiannual fluctuations in population density of small rodents have been known since antiquity. However, factors responsible for this phenomenon remain unknown (Krebs and Myers 1974, Finerty 1980, Taitt and Krebs 1985). The objectives of this long-term study are to determine whether environmental variables, possibly acting through reproductive responses, contribute to the multiannual fluctuations of the montane vole, Microtus montanus.

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