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Riverine Habitat (riverine + habitat)

Distribution by Scientific Domains

Life Sciences	88%

Selected Abstracts

Hyporheic Exchange in Mountain Rivers I: Mechanics and Environmental Effects

GEOGRAPHY COMPASS (ELECTRONIC), Issue 3 2009
Daniele Tonina
Hyporheic exchange is the mixing of surface and shallow subsurface water through porous sediment surrounding a river and is driven by spatial and temporal variations in channel characteristics (streambed pressure, bed mobility, alluvial volume and hydraulic conductivity). The significance of hyporheic exchange in linking fluvial geomorphology, groundwater, and riverine habitat for aquatic and terrestrial organisms has emerged in recent decades as an important component of conserving, managing, and restoring riverine ecosystems. Here, we review the causes and environmental effects of hyporheic exchange, and provide a simple mathematical framework for examining the mechanics of exchange. A companion paper explores the potential effects of channel morphology on exchange processes and the hyporheic environments that may result in mountain basins (Buffington and Tonina 2009). [source]

Microsatellite DNA markers reveal genetic differentiation among populations of Glossina palpalis gambiensis collected in the agro-pastoral zone of Sideradougou, Burkina Faso

INSECT MOLECULAR BIOLOGY, Issue 4 2000
P. Solano
Abstract Intraspecific genetic variability of Glossina palpalis gambiensis in the area of Sideradougou, Burkina Faso, was studied using polymorphic microsatellite DNA markers. This genetic study was combined with other epidemiological information on the same tsetse: bloodmeal identification, dissection of tsetse and molecular characterization of the trypanosomes detected. There was significant genetic differentiation among flies caught only a few kilometers apart, within the same riverine habitat. These distinct subpopulations were also differentially infected by trypanosomes. In part of the study area, a Factorial Correspondence Analysis undertaken on the genotypes allowed us to detect a Wahlund effect, suggesting the presence of tsetse originating from different source populations coming from two distinct drainage systems. The apparent structuring of populations of G. palpalis gambiensis is discussed relative to appropriate strategies to control African Trypanosomosis. [source]

The impact of elephants, Loxodonta africana, on woody vegetation through selective debarking in Samburu and Buffalo Springs National Reserves, Kenya

AFRICAN JOURNAL OF ECOLOGY, Issue 1 2010
Festus W. Ihwagi
Abstract The impact of elephants on the woody plant community through debarking was investigated in Samburu and Buffalo Springs National Reserves, Kenya. Acacia elatior Brenan, the most abundant tree species in the riverine zone, accounted for 68% (n = 1375) of woody plants. A. tortilis (Forsskal) Hayne dominated plots away from the river. Debarking incidences were significantly higher for A. elatior than for other species indicating selective utilization. The riverine zone by virtue of having more trees of the preferred species, A. elatior, had the highest debarking incidences. Presence of very few saplings along the river is attributed to both elephant trampling and herbivory by other species. An estimated 38.5% and 22.5% of the riverine A. elatior and A. tortilis trees respectively, were bound to die within the next 4,5 years because of severe debarking, ,75% of bark circumference. Debarking was positively correlated with stem circumference; the medium-sized trees being the worst affected by the elephants' selective debarking behaviour. Intense debarking incidences were recorded during the dry season. Through the elephants' selective debarking, the riverine habitat is bound to open up gradually, leading to considerable habitat change in the near future. Elephant impact on vegetation is less away from the river and increases with their densities. Résumé L'impact des éléphants sur la communauté des plantes ligneuses, à cause de l'enlèvement des écorces, a étéétudié dans les Réserves Nationales de Samburu et de Buffalo Springs, au Kenya. L'Acacia elatior Brenan, le plus abondant de la zone riveraine, comptait pour 68% (n = 1375) des plantes ligneuses. A. tortilis (Forsskal) Haine dominait les parcelles plus éloignées de la rivière. Les cas d'écorçage étaient significativement plus nombreux pour A. elatior que pour les autres espèces, ce qui indique une utilisation sélective. La zone riveraine, du fait qu'elle compte plus d'arbres de l'espèce préférée, A. elatior, comptait aussi le plus grand nombre de cas d'écorçage. La présence de très peu de jeunes plants le long de la rivière est attribuée au piétinement par les éléphants et à la consommation par d'autres espèces herbivores. On estime que respectivement 38,5% et 22,5% des A. tortilis et A. elatior de la zone riveraine devraient mourir dans les 4,5 années à venir, en raison d'écorçages sévères qui peuvent être de ,75% de la circonférence de l'arbre. L'écorçage était positivement liéà la circonférence du tronc, les arbres de diamètre moyen étant les plus gravement affectés par le comportement sélectif des éléphants. Des cas d'écorçage intense ont été enregistrés au cours de la saison sèche. En raison de l'écorçage sélectif des éléphants, l'habitat riverain est condamnéà s'ouvrir progressivement, ce qui entraînera un changement considérable dans un proche avenir. L'impact des éléphants sur la végétation est moindre lorsqu'on s'éloigne de la rivière, et il augmente en fonction de leur densité. [source]

Comparison of responses to alarm calls by patas (Erythrocebus patas) and vervet (Cercopithecus aethiops) monkeys in relation to habitat structure

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2002
Karin L. Enstam
Abstract We studied responses to alarm calls of sympatric patas (Erythrocebus patas) and vervet (Cercopithecus aethiops) monkeys in relation to habitat structure, with the intention of understanding the relationship between the environment and predator avoidance. Patas and vervet monkeys are phylogenetically closely related and overlap in body size. However, while patas monkeys are restricted to nonriverine habitats at our study site, vervets use both nonriverine and riverine habitats, allowing us to "vary" habitat structure while controlling for effects of group size, composition, and phylogeny. Patas monkeys in the nonriverine habitat responded to mammalian predator alarm calls with a greater variety of responses than did vervets in the riverine habitat, but not when compared with vervets in the nonriverine habitat. Ecological measurements confirm subjective assessments that trees in the riverine habitat are significantly taller and occur at lower densities than trees in the nonriverine habitat. Despite the lower density of trees in the riverine habitat, locomotor behavior of focal animals indicates that canopy cover is significantly greater in the riverine than the nonriverine habitat. Differences in responses to alarm calls by the same groups of vervets in different habitat types, and convergence of vervets with patas in the same habitat type, suggest that habitat type can be a significant source of variation in antipredator behavior of primates. Am J Phys Anthropol 119:3,14, 2002. © 2002 Wiley-Liss, Inc. [source]

Characterization of freshwater pearl mussel (Margaritifera margaritifera) riverine habitat using River Habitat Survey data

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 3 2003
L.C. Hastie
Abstract 1.The feasibility of using River Habitat Survey (RHS) data to describe freshwater pearl mussel (Margaritifera margaritifera) macrohabitat in the River Spey, north-east Scotland, was investigated. 2.Mussels were found to be positively associated with a number of RHS variables. These included: boulder/cobble river bed substrates, broken/unbroken standing waves (channel flow types), aquatic liverworts/mosses/lichens and broadleaf/mixed woodland/bankside tree cover. Negative associations with gravel-pebble/silt substrates and emergent reeds/sedges/herbs were also found. 3.Two binary logistic regression models, based on seven and four variables, respectively, were constructed in order to predict the presence/absence of mussels at any given site. Predictive success rates of 83% and 78% were achieved. 4.Another binary logistic regression model, based on four variables, was constructed in order to predict the occurrence of ,optimal' M. margaritifera habitat (overall mussel densities , 1 m,2). A predictive success rate of 83% was achieved. 5.The results indicate two potentially important applications of RHS for the conservation management of M. margaritifera: (1) for monitoring the effects of physical changes on extant mussel beds (and predicting their effects on mussel populations), and (2) for determining the habitat suitability of historically occupied sites for re-introductions. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Design and field methods for sighting surveys of cetaceans in coastal and riverine habitats

MAMMAL REVIEW, Issue 1 2008
STEVE DAWSON
ABSTRACT 1Dolphins and porpoises in coastal and/or riverine habitats face serious conservation threats, yet surveys of their abundance are often especially difficult due to the challenges imposed by the habitats. Because many of these species occur in developing countries, lack of resources imposes a further set of challenges. 2We offer advice on designing and conducting line-transect surveys with a focus on sound, practical, design rather than analytical sophistication, and we attempt, where possible, to offer simple, inexpensive solutions. 3We guide the reader through the questions of what kind of survey should be done, whether by boat or aircraft, and we discuss ways to avoid bias and increase precision. 4Our treatment of field methods focuses especially on robust, but low-cost, approaches. We provide two case studies to illustrate the implementation of these ideas. [source]

Comparison of responses to alarm calls by patas (Erythrocebus patas) and vervet (Cercopithecus aethiops) monkeys in relation to habitat structure

Embedding a strategic approach to river restoration in operational management processes , experiences in England,

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue S1 2010
Chris P. Mainstone
Abstract 1. The restoration of riverine habitats that have been physically modified by man has gained momentum over the past two decades, driven by a number of objectives. Formalizing the planning and implementation of such activity, however, so that it demonstrably meets national and local environmental objectives without compromising essential societal needs such as flood risk management, has proved problematic. 2. This paper addresses the operational realities of river restoration in the UK as experienced in England by the authors, and in doing so attempts to provide a vision for how strategic planning and implementation of restoration measures sensitive to these realities might be introduced. Specifically, the paper explores: the prevailing perspectives on river restoration, shaped by both legislative drivers for ecosystem and biodiversity protection and the multiple uses made of rivers, their floodplains and catchments; how decisions have tended to be made to date and how the government agencies for environmental protection and biodiversity conservation in England are planning to make decisions in the future; the key obstacles to putting in place scientifically and technically robust, large-scale, long-term, economically viable plans for river restoration; the potential for using rivers with special conservation designations for wildlife as a springboard for a strategic approach to river restoration more widely. 3. The issues hindering a strategic operational approach to river restoration in England are common to the rest of the UK and other developed countries grappling with the enormity of the river restoration challenge. To make real progress with river restoration, an operational decision-making framework is needed that promotes progressive and strategic action but at the same time gives everyone confidence that such action is realistic and worthwhile. Copyright © 2010 John Wiley & Sons, Ltd. [source]