Environment Relationships (environment + relationships)

Distribution by Scientific Domains


Selected Abstracts


Study Design for Assessing Species Environment Relationships and Developing Indicator Systems for Ecological Changesin Floodplains , The Approach of the RIVA Project

INTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 4 2006
Klaus Henle
Abstract In this article the study design and data sampling of the RIVA project , "Development and Testing of a Robust Indicator System for Ecological Changes in Floodplain Systems" , are described. The project was set up to improve existing approaches to study species environment relationships as a basis for the development of indicator systems and predictive models. Periodically flooded grassland was used as a model system. It is agriculturally used at a level of intermediate intensity and is the major habitat type along the Middle Elbe, Germany. We chose a main study area to analyse species environment relationships and two reference sites for testing the transferability of the results. Using a stratified random sampling scheme, we distributed 36 study plots across the main study site and 12 plots each within the reference sites. In each of the study plots, hydrological and soil variables were measured and plants, molluscs, and carabid beetles were sampled. Hoverflies were collected on a subset of the sampling plots. A brief summary of first results is then provided. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Vegetation,environment relationships along El-Salam Canal, Egypt

ENVIRONMETRICS, Issue 3 2001
Mamdouh S. Serag
Abstract The bank and open water vegetation along El-Salam Canal in north-eastern Egypt were studied in relation to the prevailing environmental factors. The hypothesis that terresterial and aquatic species would show different downstream patterns of species richness was tested by sampling species composition and environmental variables along 80,km of the canal. Species richness was highest in the first 30,km of the canal. The downstream decrease in species richness exhibits interpretable downstream patterns. Total species richness increased with increasing organic matter in the soil and decreased with both increasing soil and water salinity along the gradient. The indicator species of TWINSPAN analysis are: Azolla filiculoides, Echinochloa stagnina, Eichhornia crassipes and Saccharum spontaneum (cluster I); Ceratophyllum demersum, Ludwigia stolonifera and Typha domingensis (cluster II); Potamogeton pectinatus and Phragmites australis (cluster III); Tamarix nilotica and Suaeda vera (cluster IV). The environmental factors influencing the vegetation clusters were analysed using canonical correspondence analysis ordination (CCA). The water salinity, total nitrogen and total phosphorus appeared to be the most important factors controlling the abundance of aquatic plant distribution along the canal. The shoreline vegetation is mainly controlled by salinity, K+ and organic carbon of the soil. Water analysis indicated that the salinity of the water increases southwards and the minimum salinity of the water (0.78,mS/cm) was recorded at the intake of the canal. The maximum value (7.5,mS/cm) of water salinity was recorded near the Suez Canal. Copyright © 2001 John Wiley & Sons, Ltd. [source]


Species co-occurrence, nestedness and guild,environment relationships in stream macroinvertebrates

FRESHWATER BIOLOGY, Issue 9 2009
2Article first published online: 2 JUN 200, JANI HEINO
Summary 1. Describing species distribution patterns and the underlying mechanisms is at the heart of ecological research. A number of recent studies have used null model approaches to explore mechanisms behind spatial variation in community structure. 2. However, unexplored questions are the degree to which single guilds of potentially competing stream macroinvertebrate species show: (i) interspecific segregation among-stream sites (i.e. occur together less often than expected by chance), suggesting competitive interactions; (ii) interspecific aggregation (i.e. occur together more often than expected by chance), suggesting similar responses to the environment; (iii) comply with nestedness, suggesting the existence of selective extinctions or colonisations and (iv) show similar environmental relationships. 3. The present analyses showed that guilds of stream macroinvertebrates exhibit non-random co-occurrence patterns that were generally contingent on the weighting of sites by stream size. Despite significant segregation of species, each guild also showed significantly nested patterns. Species richness was correlated with different environmental factors between the guilds, although these correlations were relatively low. By contrast, correlations between the major ordination axes and key environmental variables were slightly stronger in canonical correspondence analysis, and generally the same factors were most strongly correlated with variation in the species composition of each guild. 4. The present findings are the first to show that species within each stream macroinvertebrate guild show significant negative co-occurrence at the among-stream riffle scale. These findings present challenges for future studies that aim to disentangle whether these patterns comply with the habitat checkerboard or the competitive checkerboard explanations. [source]


Functional biodiversity of macroinvertebrate assemblages along major ecological gradients of boreal headwater streams

FRESHWATER BIOLOGY, Issue 9 2005
JANI HEINOArticle first published online: 3 AUG 200
Summary 1. Biodiversity,environment relationships are increasingly well-understood in the context of species richness and species composition, whereas other aspects of biodiversity, including variability in functional diversity (FD), have received rather little rigorous attention. For streams, most studies to date have examined either taxonomic assemblage patterns or have experimentally addressed the importance of species richness for ecosystem functioning. 2. I examined the relationships of the functional biodiversity of stream macroinvertebrates to major environmental and spatial gradients across 111 boreal headwater streams in Finland. Functional biodiversity encompassed functional richness (FR , the number of functional groups derived from a combination of functional feeding groups and habit trait groups), FD , the number of functional groups and division of individuals among these groups, and functional evenness (FE , the division of individuals among functional groups). Furthermore, functional structure (FS) comprised the composition and abundance of functional groups at each site. 3. FR increased with increasing pH, with additional variation related to moss cover, total nitrogen, water colour and substratum particle size. FD similarly increased with increasing pH and decreased with increasing canopy cover. FE decreased with increasing canopy cover and water colour. Significant variation in FS was attributable to pH, stream width, moss cover, substratum particle size, nitrogen, water colour with the dominant pattern in FS being related to the increase of shredder-sprawlers and the decrease of scraper-swimmers in acidic conditions. 4. In regression analysis and redundancy analysis, variation in functional biodiversity was not only related to local environmental factors, but a considerable proportion of variability was also attributable to spatial patterning of environmental variables and pure spatial gradients. For FR, 23.4% was related to pure environmental effects, 15.0% to shared environmental and spatial effects and 8.0% to spatial trends. For FD, 13.8% was attributable to environmental effects, 15.2% to shared environmental and spatial effects and 5% to spatial trends. For FE, 9.0% was related to environmental variables, 12.7% to shared effects of environmental and spatial variables and 4.5% to spatial variables. For FS, 13.5% was related to environmental effects, 16.9% to shared environmental and spatial effects and 15.4% to spatial trends. 5. Given that functional biodiversity should portray variability in ecosystem functioning, one might expect to find functionally rather differing ecosystems at the opposite ends of major environmental gradients (e.g. acidity, stream size). However, the degree to which variation in the functional biodiversity of stream macroinvertebrates truly portrays variability in ecosystem functioning is difficult to judge because species traits, such as feeding roles and habit traits, are themselves strongly affected by the habitat template. 6. If functional characteristics show strong responses to natural environmental gradients, they also are likely to do so to anthropogenic environmental changes, including changes in habitat structure, organic inputs and acidifying elements. However, given the considerable degree of spatial structure in functional biodiversity, one should not expect that only the local environment and anthropogenic changes therein are responsible for this variability. Rather, the spatial context, as well as natural variability along environmental gradients, should also be explicitly considered in applied research. [source]


Study Design for Assessing Species Environment Relationships and Developing Indicator Systems for Ecological Changesin Floodplains , The Approach of the RIVA Project

INTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 4 2006
Klaus Henle
Abstract In this article the study design and data sampling of the RIVA project , "Development and Testing of a Robust Indicator System for Ecological Changes in Floodplain Systems" , are described. The project was set up to improve existing approaches to study species environment relationships as a basis for the development of indicator systems and predictive models. Periodically flooded grassland was used as a model system. It is agriculturally used at a level of intermediate intensity and is the major habitat type along the Middle Elbe, Germany. We chose a main study area to analyse species environment relationships and two reference sites for testing the transferability of the results. Using a stratified random sampling scheme, we distributed 36 study plots across the main study site and 12 plots each within the reference sites. In each of the study plots, hydrological and soil variables were measured and plants, molluscs, and carabid beetles were sampled. Hoverflies were collected on a subset of the sampling plots. A brief summary of first results is then provided. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Homogenization of forest plant communities and weakening of species,environment relationships via agricultural land use

JOURNAL OF ECOLOGY, Issue 3 2007
MARK VELLEND
Summary 1Disturbance may cause community composition across sites to become more or less homogenous, depending on the importance of different processes involved in community assembly. In north-eastern North America and Europe local (alpha) diversity of forest plants is lower in forests growing on former agricultural fields (recent forests) than in older (ancient) forests, but little is known about the influence of land-use history on the degree of compositional differentiation among sites (beta diversity). 2Here we analyse data from 1446 sites in ancient and recent forests across 11 different landscapes in north-eastern North America and Europe to demonstrate decreases in beta diversity and in the strength of species,environment relationships in recent vs. ancient forests. 3The magnitude of environmental variability among sites did not differ between the two forest types. This suggests the difference in beta diversity between ancient and recent forests was not due to different degrees of environmental heterogeneity, but rather to dispersal filters that constrain the pool of species initially colonizing recent forests. 4The observed effects of community homogenization and weakened relationships between species distributions and environmental gradients appear to persist for decades or longer. The legacy of human land-use history in spatial patterns of biodiversity may endure, both within individual sites and across sites, for decades if not centuries. [source]


The impact of changing olive cultivation practices on the ground flora of olive groves in the Messara and Psiloritis regions, Crete, Greece

LAND DEGRADATION AND DEVELOPMENT, Issue 3 2006
H. D. Allen
Abstract This paper examines the impact that different olive cultivation practices have on the nature of the ground flora of olive groves in the region of the Psiloritis massif and Messara Plain in central and southern Crete, Greece. In lower, flatter areas there are areas of both traditional and intensive forms of olive cultivation. In more marginal, upland areas there are traditional terraced olive groves, some of which are being abandoned. The relationship between the vegetation composition of the ground flora and environmental variables was established, by means of TWINSPAN® and ordination analysis, using survey data from nineteen sites across the region. Four vegetation communities are identified: olive with herbaceous taxa; olive with sclerophyllous shrub taxa; and two forms of sclerophyllous shrub communities. Ordination results indicate that environmental variables, such as soil characteristics, slope aspect and slope angle, explain about 60,per,cent of the species,environment relationships. The remaining variation in species composition is interpreted to be the result of different cultivation practices. The implications for land degradation are examined, in particular the changes in vegetation diversity of both intensive and semi-abandoned olive groves, the potential for increased soil erosion, and the risk of fire as a result of increased fuel loading as flammable shrubs invade abandoned terraces. Intensification of olive cultivation in Crete, and across the Mediterranean, has been encouraged by subsidies from the European Union leading to rapid landscape change. Thus there is a need to monitor changes in olive cultivation practices both at the local scale, by means of ground-based fieldwork, and at landscape and regional scales, by means of remote sensing. Copyright © 2006 John Wiley & Sons, Ltd. [source]


Periglacial distribution modelling with a boosting method

PERMAFROST AND PERIGLACIAL PROCESSES, Issue 1 2009
Jan Hjort
Abstract We assessed the applicability of a boosting method in periglacial distribution modelling using empirically derived data on cryoturbation, sporadic permafrost and sorted solifluction from an area of 600,km2 in sub-Arctic Finland. The main aims were: (1) to compare the predictive ability of the generalised boosting method used with more common parametric techniques (generalised linear model) and machine-learning methods (artificial neural networks) and (2) to assess the tenability of the explanatory variables highlighted by the generalised boosting method. The results showed the robustness of the boosting method in predicting the distribution of periglacial phenomena in the sub-Arctic landscape. Furthermore, the environmental factors selected by the boosting method coincided well with the expected controls of the phenomena. The strengths of the generalised boosting method lie in its high predictive ability, flexibility in capturing complex process-environment relationships and realistic model outcomes. Copyright © 2008 John Wiley & Sons, Ltd. [source]


Sustainable development in drylands: geographical contributions to a better understanding of people,environment relationships

THE GEOGRAPHICAL JOURNAL, Issue 3 2002
David Thomas
[source]


Species richness,environment relationships within coastal sclerophyll and mesophyll vegetation in Ku-ring-gai Chase National Park, New South Wales, Australia

AUSTRAL ECOLOGY, Issue 4 2003
Andrew F. Le Brocque
Abstract Patterns in species richness from a wide range of plant communities in Ku-ring-gai Chase National Park, New South Wales, Australia, were examined in relation to a number of environmental variables, including soil physical and chemical characteristics. Total species richness and richness of three growth-form types (trees, shrubs and ground cover) were determined in duplicate 500-m2 quadrats from 50 sites on two geological substrata: Hawkesbury Sandstone and Narrabeen shales and sandstones. Generalized linear models (GLM) were used to determine the amount of variation in species richness that could be significantly explained by the measured environmental variables. Seventy-three per cent of the variation in total species richness was explained by a combination of soil physical and chemical variables and site attributes. The environmental variables explained 24% of the variation in tree species richness, 67% of the variation in shrub species richness and 62% of the variation in ground cover species richness. These results generally support the hypothesis of an environmental influence on patterns in total species richness and richness of shrubs and ground cover species. However, tree species richness was not adequately predicted by any of the measured environmental variables; the present environment exerts little influence on the richness of this growth-form type. Historical factors, such as fire or climatic/environmental conditions at time of germination or seedling establishment, may be important in determining patterns in tree species richness at the local scale. [source]


Habitat associations of Atlantic herring in the Shetland area: influence of spatial scale and geographic segmentation

FISHERIES OCEANOGRAPHY, Issue 3 2001
CHRISTOS D. Maravelias
This study considers the habitat associations of a pelagic species with a range of biotic and abiotic factors at three different spatial scales. Generalized additive models (GAM) are used to analyse trends in the distributional abundance of Atlantic herring (Clupea harengus) in relation to thermocline and water depth, seabed roughness and hardness, sea surface salinity and temperature, zooplankton abundance and spatial location. Two geographical segments of the population, those east and west of the Shetland Islands (northern North Sea, ICES Div IVa), are examined. The differences in the ecological preferences of the species in these two distinct geographical areas are elucidated and the degree that these environmental relationships might be modulated by the change of support of the data is also considered. Part of the observed variability of the pre-spawning distribution of herring was explained by different parameters in these two regions. Notwithstanding this, key determinants of the species' spatial aggregation in both areas were zooplankton abundance and the nature of the seabed substrate. The relative importance of the variables examined did not change significantly at different spatial scales of the observation window. The diverse significance of various environmental factors on herring distribution was attributed mainly to the interaction of species' dynamics with the different characteristics of the ecosystem, east and west of the Shetland Islands. Results suggest that the current 2.5 nautical miles as elementary sampling distance unit (ESDU) is a reasonable sampling scheme that combines the need to reduce the data volume while maintaining spatial resolution to distinguish the species/environment relationships. [source]