scholarly journals Identification of Fine-Scale Marine Benthic Ecoclines by Multiple Parallel Ordination

2014 ◽  
Vol 2014 ◽  
pp. 1-23 ◽  
Author(s):  
Thijs Christiaan van Son ◽  
Rune Halvorsen ◽  
Karl Norling ◽  
Torgeir Bakke ◽  
Maria Kaurin ◽  
...  
Keyword(s):  
Species Composition ◽  
Environmental Variables ◽  
Gradient Analysis ◽  
Detrended Correspondence Analysis ◽  
Natural Ecosystems ◽  
Form Complex ◽  
Indirect Gradient Analysis ◽  
Physical Forcing ◽  
Periodic Hypoxia ◽  
Geomorphological Features

The species-environment relationship is a fundamental structural property of natural ecosystems. Marine sedimentary macrofauna is known to be structured by a range of environmental variables; however, the mechanisms by which environmental variables covary to form complex-gradients (i.e., groups of intercorrelated environmental variables), and how these are related to coenoclines (i.e., gradients in species composition), remain poorly understood. We classified our study area into geomorphological features that were used for stratified sampling of macrofaunal polychaetes, molluscs, and echinoderms. The resulting species-by-site matrix was subjected to indirect gradient analysis by a multiple parallel ordination strategy, using detrended correspondence analysis and nonmetric multidimensional scaling. One major and one minor coenocline were identified. Based on the correlation between complex-gradients and the main coenocline we hypothesise the existence of two ecoclines that we have termedPeriodic hypoxiaandPeriodic physical forcing. We conclude that a combination of recurrent (periodical) and extreme events is likely to determine the variation found in the species composition of marine sedimentary ecosystems. Based on the results of our study, we conclude that indirect gradient analysis is a useful tool for enhancement of our basic mechanistic understanding of the processes governing the compositional structure of marine sediment communities.

Indirect gradient analysis of the Mangal formation of Gazi bay (Kenya)

1989 ◽  
Vol 54 ◽  
Author(s):  
H. Beeckman ◽  
E. Gallin ◽  
E. Coppejans
Keyword(s):  
Correspondence Analysis ◽  
Gradient Analysis ◽  
Stomatal Density ◽  
Detrended Correspondence Analysis ◽  
Zonation Pattern ◽  
Mangrove Species ◽  
Indirect Gradient Analysis ◽  
Ordination Method ◽  
Gazi Bay

(1)  Based on vegetation relevés of sample units along transects perpendicular to  the coastline, the mangal ecosystem of Gazi Bay (Kenya) has been  investigated.     (2) An indirect gradient analysis is performed by the ordination method  Detrended Correspondence Analysis.     (3) The first ordination axis can be interpreted in terms of resistance of  the different species to flooding.     (4) A similar zonation pattern is found as described by WALTER &  STEINER (1936).     (5) Zonation is closely connected with morphological and ecophysiological  features of the mangrove species. Therefore stomatal density has been  measured. Sonneratia has by  far the lowest stomatal density, Lumnitzera the highest.

Phytosociology and gradient analysis of a subalpine treed fen in Rocky Mountain National Park, Colorado

1996 ◽  
Vol 74 (8) ◽  
pp. 1203-1213 ◽  
Author(s):  
J. Bradley Johnson
Keyword(s):  
Species Composition ◽  
Correspondence Analysis ◽  
Species Distribution ◽  
Gradient Analysis ◽  
Vegetation Type ◽  
Detrended Correspondence Analysis ◽  
Tree Density ◽  
Small Scale ◽  
Groundwater Temperature ◽  
Strong Control

The vegetation of a subalpine fen in Colorado was studied. Insight was sought into the community structure and factors influencing species distribution of a vegetation type heretofore undescribed in the southern Rocky Mountains. A vegetational gradient was evaluated using detrended correspondence analysis (DCA). Four types of vegetation were subjectively defined; these same types were distinguished by the DCA. DCA further revealed marked differences in the vegetation occurring on peat hummocks versus in hollows. Species composition was related to environment using canonical correspondence analysis (CCA). Water-table depth, hummock height, shading, groundwater temperature, and conductivity were significantly correlated with species distribution, accounting for 51% of the total species variance. Univariate regression was used to examine how tree density varied with environment. The above factors, except for shading and conductivity, were also significantly correlated with tree density. It is suggested that the peat hummocks that form on this moderate fen provide an environment similar to that of an ombrotrophic bog and that these "miniature bogs" form in areas unable to support expansive bogs. Further, these hummocks provide small-scale environmental heterogeneity that exerts a strong control over species composition that would not be evident in studies based on samples of a large areal extent. Keywords: Colorado, gradient analysis, ordination, heterogeneity, peatlands, phytosociology.

Understory vegetation in northern Ontario jack pine and black spruce plantations: 20-year successional changes

2003 ◽  
Vol 33 (9) ◽  
pp. 1791-1803 ◽  
Author(s):  
Shelley L Hunt ◽  
Andrew M Gordon ◽  
Dave M Morris ◽  
George T Marek
Keyword(s):  
Species Composition ◽  
Environmental Variables ◽  
Black Spruce ◽  
Detrended Correspondence Analysis ◽  
Jack Pine ◽  
Understory Vegetation ◽  
Rate Of Change ◽  
Northern Ontario ◽  
Pine Stands ◽  
Over Time

The 20-year successional development of understory vegetation was investigated in jack pine (Pinus banksiana Lamb.) and black spruce (Picea mariana (Mill.) BSP) plantations in northern Ontario, in relation to stand species composition, species diversity, and the rate of change in stands of different post-disturbance ages. Detrended correspondence analysis (DCA) ordination of plantation stands using species composition data from 1978 and 1998 indicated variation among stands in directions and rates of change in species composition over time. Rank correlations of environmental variables with the DCA axes suggested a light–moisture gradient along the first axis, driven by soil texture and overstory species, and a gradient representing time since disturbance and stand development along the second axis. Although overall beta diversity among stands remained constant over time, some convergence was found among a smaller group of stands, and divergence was noted between spruce and pine stands. Species composition also became more highly correlated with environmental variables through time. From 1978 to 1998, species richness increased in young, dry pine stands; decreased in older, dry pine stands; and decreased in young spruce stands. The understory vegetation in stands on mesic sites was more diverse than that on dry, sandy sites at both times. The rate of change in understory species composition slowed with time after disturbance, indicating an increasing stability in micro en vi ron men tal conditions as the influence of harvesting disturbance became weaker with time.

scholarly journals Habitat structure and small mammals abundances in one semiarid landscape in the Brazilian Caatinga

2005 ◽  
Vol 22 (1) ◽  
pp. 119-129 ◽  
Author(s):  
Rodrigo R. Freitas ◽  
Pedro Luís B. da Rocha ◽  
Paulo César Simões-Lopes
Keyword(s):  
Small Mammals ◽  
Environmental Variables ◽  
Habitat Structure ◽  
Gradient Analysis ◽  
Direct Analysis ◽  
Indirect Gradient Analysis ◽  
Mammal Fauna ◽  
Highly Correlated ◽  
Academy Of Sciences ◽  
Major Project

Studies conducted under a major project sponsored by the Brazilian Academy of Sciences in the 1970's concluded that the small mammal fauna of the semiarid Caatinga region of Brazil is impoverished and highly restricted to mesic granite outcroppings due to the lack of water conserving physiological capabilities in its species. This work focuses the abundance of small mammals in five typical Caatinga habitats. Indirect gradient analysis shows that three theoretical environmental variables explain most of the variance present in the community abundance matrix. Direct analysis of gradients show that none of these variables is highly correlated to availability of granite outcroppings. Our data also suggest that the abundances in Caatinga are not particularly low when compared to neighbor biomes and that underlying factors of habitat use by Caatinga small mammals are more complex than previously supposed.

scholarly journals Ecological Evaluation of Grassland Vegetation in Hodrušská Hornatina Highland

2020 ◽  
Vol 39 (3) ◽  
pp. 236-249
Author(s):  
Alexandra Klimantová
Keyword(s):  
Species Composition ◽  
Environmental Variables ◽  
Environmental Gradient ◽  
Detrended Correspondence Analysis ◽  
Grassland Vegetation ◽  
Ecological Evaluation ◽  
Factors Affecting ◽  
Phytosociological Relevés ◽  
Grassland Communities

AbstractIn the submitted paper, we have analysed the results of a systematic survey of grassland communities, performed in Hodrušská hornatina highland, in Štiavnické vrchy mountains. The main aims of the research were: i) syntaxonomical classification of grassland vegetation; ii) analysis of the main ecological gradients in species composition; iii) evaluation of the influence of environmental factors on species composition of grasslands. The dataset included 153 phytosociological relevés recorded on grasslands. Grassland communities were classified within five associations: Holcetum lanati, Pastinaco sativae-Arrhenatheretum elatioris, Alchemillo-Arrhenatheretum elatioris, Anthoxantho odorati-Agrostietum tenuis, Onobrychido viciifoliae-Brometum erecti; and the successional and transitional stages belonging to alliances Arrhenatherion elatioris and Bromion erecti. The results of the Detrended Correspondence Analysis support our assumption that the main environmental gradient in species composition on grassland is related to moisture. The results of the Redundancy Analysis show that all used environmental variables explained 3.4% of the variability of the species data. The most important factors affecting the species composition were altitude, slope, distance from settlements, and management.

scholarly journals ФІТОПАРАЗИТИЧНІ НЕМАТОДИ ПРИРОДНИХ ЕКОСИСТЕМ ЛІВОБЕРЕЖНОГО ПОЛІССЯ (У МЕЖАХ ЧЕРНІГІВСЬКОЇ ОБЛАСТІ)

2020 ◽  
Vol 79 (1-2) ◽  
pp. 42-47
Author(s):  
V. L. Shevchenko ◽  
T. M. Zhylina
Keyword(s):  
Species Composition ◽  
Left Bank ◽  
Frequency Of Occurrence ◽  
Soil Nematodes ◽  
Natural Ecosystems ◽  
Dominant Group ◽  
Nature Park ◽  
Nematode Abundance ◽  
Longidorus Elongatus ◽  
Eleven Species

The species composition, frequency of occurrence, and the abundance of phytohelminths in communities of soil nematodes in natural ecosystems of the Left-Bank Polissia (Chernihiv region) were studied. Samples were collected throughout 2011-2016 in forest and meadow ecosystems on the territory of Chernihivskyi, Horodnianskyi, Kozeletskyi, Koropskyi, Menskyi, Ripkynskyi, Sosnytskyi, Semenivskyi, Shchorskyi and Novhorod-Siverskyi districts. Nematodes were extracted by a modified Baermann’s method from the 20-g sample. The exposition time was 48 h. Extracted nematodes were fixed in the triethanolamine–formalin (TAF, 2 % triethanolamine, 7 % formaldehyde solution, 91% water), and mounted on the temporary hydroglyceric slides. Nematode abundance was expressed as specimens per 100 g of dry soil. Seventeen species from three orders, ten families and fifteen genera were found. Eleven species (64.7 % of the species composition) belonged to the order of Tylenchida, four (23.5 %) – Triplonchida, two (11.8 %) – Dorylaimida. Eleven species (Gracilacus audriellus, Paratylenchus nanus, Tylenchorhynchus dubius, Helicotylenchus dihystera, Macroposthonia annulata, Diphtherophora communis, Trichodorus primitivus, Paratrichodorus teres, Paratrichodorus pachydermus, Longidorus elongatus, Xiphinema index) are ectoparasites, three species (Ditylenchus dipsaci, Pratylenchus pratensis, Hirschmaniella gracilis) – endoparasites, and three species (Hemicycliophora sp., Heterodera sp. 1, Heterodera sp. 2) – semiendoparasites. Phytohelminths in communities of soil nematodes in forest ecosystems ranged from 9.4 to 26.3 %. But in meadow ecosystems of the Mezin National Nature Park it was a dominant group (proportion in the community 47%). The most frequent species were G. audriellus, H. dihystera and T. dubius which occurred in 33.3 %, 33.3 % and 28.3 % of samples respectively. P. nanus, D. dipsaci, P. pratensis та D. communis – had frequency of occurrence 15 – 20%. Ten species of phytohelminths were found in 1–4 ecosystems (1.7–6.7%). G. audriellus and H. dihystera were abundant (124 and 56 specimens per 100 g of soil respectively).

What drives plant biodiversity in the clay floodplain grasslands of NSW?

2009 ◽  
Vol 31 (3) ◽  
pp. 329 ◽  
Author(s):  
Tom Lewis ◽  
Peter J. Clarke ◽  
Ralph D. B. Whalley ◽  
Nick Reid
Keyword(s):  
Species Richness ◽  
Species Composition ◽  
Soil Type ◽  
Environmental Variables ◽  
Private Property ◽  
Flood Frequency ◽  
Perennial Grasses ◽  
Plant Biodiversity ◽  
South Wales ◽  
Plant Families

An assessment of the relative influences of management and environment on the composition of floodplain grasslands of north-western New South Wales was made using a regional vegetation survey sampling a range of land tenures (e.g. private property, travelling stock routes and nature reserves). A total of 364 taxa belonging to 55 different plant families was recorded. Partitioning of variance with redundancy analysis determined that environmental variables accounted for a greater proportion (61.3%) of the explained variance in species composition than disturbance-related variables (37.6%). Soil type (and fertility), sampling time and rainfall had a strong influence on species composition and there were also east–west variations in composition across the region. Of the disturbance-related variables, cultivation, stocking rate and flooding frequency were all influential. Total, native, forb, shrub and subshrub richness were positively correlated with increasing time since cultivation. Flood frequency was positively correlated with graminoid species richness and was negatively correlated with total and forb species richness. Site species richness was also influenced by environmental variables (e.g. soil type and rainfall). Despite the resilience of these grasslands, some forms of severe disturbance (e.g. several years of cultivation) can result in removal of some dominant perennial grasses (e.g. Astrebla spp.) and an increase in disturbance specialists. A simple heuristic transitional model is proposed that has conceptual thresholds for plant biodiversity status. This knowledge representation may be used to assist in the management of these grasslands by defining four broad levels of community richness and the drivers that change this status.

scholarly journals Environmental filtering and spillover explain multi-species edge responses across agricultural boundaries in a biosphere reserve

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
J. van Schalkwyk ◽  
J. S. Pryke ◽  
M. J. Samways ◽  
R. Gaigher
Keyword(s):  
Species Richness ◽  
Species Composition ◽  
Habitat Quality ◽  
Environmental Variables ◽  
Natural Habitat ◽  
Environmental Filtering ◽  
Biosphere Reserve ◽  
Natural Habitats ◽  
Habitat Specificity ◽  
Induced Changes

Abstract To ensure integrity of protected areas we need to understand how species respond to anthropogenic borders. We investigate, from a metacommunity perspective, the direct and indirect mechanisms by which transformed areas affect distribution patterns of ground-living arthropod assemblages inhabiting an extensive protected area adjacent to fruit orchards in an important biosphere reserve. Arthropods and environmental variables were sampled along transects perpendicular to natural-orchard edges. Influence of distance from orchard boundary, degree of impermeability of the boundary, orchard habitat quality (local scale land-use intensity), and edge-induced changes in local environmental variables on arthropod species richness and composition in non-crop habitats were assessed. Arthropod groups were assessed in terms of habitat fidelity: species associated with natural habitat (stenotopic species), those within crop habitat (cultural species), and those showing no preference for either habitat (ubiquitous species). Spillover resulted in higher cultural species richness near edges, but not higher overall species richness. Environmental filtering was important for stenotopic species composition, which was influenced by edge-induced changes in environmental variables. Ubiquitous species composition was determined by orchard impermeability. Increased orchard habitat quality was associated with higher cultural and ubiquitous species richness. The effects of orchards on assemblages in natural habitats can be variable, but predictable when using species habitat specificity in conjunction with a metacommunity framework. High intensity orchards may act as sink habitats, especially for species that readily disperse between crop and natural habitats. Here we recommend that local buffer strips are > 85 m wide, which will reduce the influence of cultural species spillover on sensitive natural ecosystems.

Effect of Water Body Morphology on Phytoplankton Biomass and Species Composition

2013 ◽  
Vol 777 ◽  
pp. 375-379
Author(s):  
Yue Hong Zhang ◽  
Fei Peng Li ◽  
Hu Hu Zhao ◽  
Hai Ping Zhang
Keyword(s):  
Species Composition ◽  
Water Body ◽  
Environmental Variables ◽  
Phytoplankton Biomass ◽  
Population Variation ◽  
Nutrient Concentrations ◽  
Body Morphology ◽  
Key Factor ◽  
Lake Type ◽  
River Type

Environmental variables, phytoplankton biomass and species composition in Nanhu Lake in Yingdong Village, Chongming Island were monitored from August 2010 to September 2011. The relationship between environmental variables and population variation of phytoplankton was discussed. The results showed that water body morphology was the key factor leading to the variation of phytoplankton community. In river-type waters the level of phytoplankton biomass was generally higher than that in lake-type waters, especially in summer. During the period of seasonal change, in river-type waters Cyanophyta dominated longer with the succession from Cyanophyta to Chlorophyta and Bacillariophyta occurred later than that in lake-type waters. Redundancy analysis (RDA) indicated that the morphology of enclosed waters had influence on phytoplankton biomass and species composition. One of the mechanisms may be that water body morphology could have impact on the growth and species dynamics of phytoplankton indirectly by affecting nutrient concentrations.

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