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Dry Lands (dry + land)
Selected AbstractsA staggered conservative scheme for every Froude number in rapidly varied shallow water flowsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 12 2003G. S. Stelling Professor Abstract This paper proposes a numerical technique that in essence is based upon the classical staggered grids and implicit numerical integration schemes, but that can be applied to problems that include rapidly varied flows as well. Rapidly varied flows occur, for instance, in hydraulic jumps and bores. Inundation of dry land implies sudden flow transitions due to obstacles such as road banks. Near such transitions the grid resolution is often low compared to the gradients of the bathymetry. In combination with the local invalidity of the hydrostatic pressure assumption, conservation properties become crucial. The scheme described here, combines the efficiency of staggered grids with conservation properties so as to ensure accurate results for rapidly varied flows, as well as in expansions as in contractions. In flow expansions, a numerical approximation is applied that is consistent with the momentum principle. In flow contractions, a numerical approximation is applied that is consistent with the Bernoulli equation. Both approximations are consistent with the shallow water equations, so under sufficiently smooth conditions they converge to the same solution. The resulting method is very efficient for the simulation of large-scale inundations. Copyright © 2003 John Wiley & Sons, Ltd. [source] Complex phylogeographic patterns in the freshwater alga Synura provide new insights into ubiquity vs. endemism in microbial eukaryotesMOLECULAR ECOLOGY, Issue 19 2010SUNG MIN BOO Abstract The global distribution, abundance, and diversity of microscopic freshwater algae demonstrate an ability to overcome significant barriers such as dry land and oceans by exploiting a range of biotic and abiotic colonization vectors. If these vectors are considered unlimited and colonization occurs in proportion to population size, then globally ubiquitous distributions are predicted to arise. This model contrasts with observations that many freshwater microalgal taxa possess true biogeographies. Here, using a concatenated multigene data set, we study the phylogeography of the freshwater heterokont alga Synura petersenii sensu lato. Our results suggest that this Synura morphotaxon contains both cosmopolitan and regionally endemic cryptic species, co-occurring in some cases, and masked by a common ultrastructural morphology. Phylogenies based on both proteins (seven protein-coding plastid and mitochondrial genes) and DNA (nine genes including ITS and 18S rDNA) reveal pronounced biogeographic delineations within phylotypes of this cryptic species complex while retaining one clade that is globally distributed. Relaxed molecular clock calculations, constrained by fossil records, suggest that the genus Synura is considerably older than currently proposed. The availability of tectonically relevant geological time (107,108 years) has enabled the development of the observed, complex biogeographic patterns. Our comprehensive analysis of freshwater algal biogeography suggests that neither ubiquity nor endemism wholly explains global patterns of microbial eukaryote distribution and that processes of dispersal remain poorly understood. [source] Genetic pattern of the recent recovery of European otters in southern FranceECOGRAPHY, Issue 2 2008Xavier Janssens We investigated how landscape affects the population genetic structure and the dispersal of the elusive European otter Lutra lutra in a contemporary colonization context, over several generations and at the level of hydrographic basins. Our study area included 10 basins located in the Cévennes National Park (CNP), at the southern front of the natural otter recovery in France. Each basin comprised 50 to 300 km of permanent rivers that were surveyed for otter presence from 1991 to 2005. Faecal samples collected in 2004 and 2005 in this area were genotyped at 9 microsatellite loci, resulting in the identification of 70 genetically distinct individuals. Bayesian clustering methods were used to infer genetic structure of the populations and to compare recent gene flow to the observed colonization. At the regional level, we identified 2 distinct genetic clusters (NE and SW; FST=0.102) partially separated by ridges, suggesting that the CNP was recolonized by 2 genetically distinct otter populations. At the basin level, the genetic distance between groups of individuals in different basins was positively correlated to the mean slope separating these basins. The probable origins and directions of individual movements (i.e. migration between clusters and basin colonization inside clusters) were inferred from assignment tests. This approach shows that steep and dry lands can stop, impede or divert the dispersal of a mobile carnivore such as the otter. [source] Desert environments: landscapes and stratigraphyGEOLOGY TODAY, Issue 5 2009Peter G. Fookes It is common to think of hot deserts, i.e. hot arid or dry lands, as areas of little rain situated in the middle parts of the world, that are simply ,just there'. However, most of the world's deserts have a long geological history, sometimes of 50 million years or more and ways have been developing for some time now, particularly from geomorphological studies, of not only erecting the law of superposition of strata for the desert but also ,absolute' dating. The authors have often worked commercially in deserts world-wide but their recent experiences in the Oman have brought home to them the excellent work that has been going on in the last two or three decades in evaluating the geological history of deserts. The Oman experience is described in a feature in the next issue. [source] Farmers' perception of treated paper mill effluent irrigationLAND DEGRADATION AND DEVELOPMENT, Issue 3 2010P. N. Rekha Abstract The utilization of treated paper mill effluents for irrigation offers many benefits such as conservation of water resources, conversion of barren land into irrigated area, addition of nutrients to the soil and plant and above all the reduction of pollution of inland water bodies. However, the utility of this effluent irrigation programme depends mainly on farmers' acceptability, adoption and management of the scheme. Knowledge about the farmers' perception is thus very much imperative for further advocacy of the effluent irrigation programme. The determinants of farmers' perception of treated paper mill effluent irrigation is a pre-requisite for the formulation of better programmes and strategies for the support of an unobstructed adoption and for the long-term sustainability of effluent irrigation schemes. The present study was conducted to assess the farmers' perception and the determinants that influence the adoption of treated paper mill effluent irrigation by interviewing a random sample of 120 farmers, using a well-structured interview schedule in paper mill effluent irrigated area in Tamil Nadu in India. The study revealed that there exists positive significant correlation between the perception and the characteristics of the farmers viz. educational status, farm size, annual income, mass media exposure, innovativeness and risk orientation. The response analysis of the perception revealed that treated paper mill effluent as alternative assured supply of irrigation water, conversion of elevated dry lands to irrigated land, changing of cropping pattern to sugarcane, increase in socioeconomic status of the farmers, incentives and technical inputs by the paper mill authorities and above all farmers' participation in planning, implementation and management of the effluent irrigation schemes influenced the farmers to form positive perception. Copyright © 2010 John Wiley & Sons, Ltd. [source] | |||||||||||||