Home About us Contact
|
Home About us Contact | ||
|
|
||
Large Temporal (large + temporal)
Selected AbstractsEvaluating the adaptability of herbage species to environmental variation through a long-term grazing experimentGRASSLAND SCIENCE, Issue 4 2005Yiruhan Abstract Mixtures of orchard grass, perennial ryegrass, tall fescue, redtop, Kentucky bluegrass and white clover were sown in the autumn of 1973. Two 8-year grazing experiments were carried out at the National Grassland Research Institute (Nasushiobara, Tochigi, Japan) to determine the effects of grazing intensity and nitrogen levels on the pasture ecosystem: two different grazing intensities (1974,1981) and two different nitrogen levels (1982,1989). Large temporal and spatial variations in phytomass were observed in both experiments. To clarify the adaptability of the phytomass of the herbage species to environmental variations in year, season and treatments, we re-examined the data obtained in these two experiments using a Finlay-Wilkinson analysis. Orchard grass and tall fescue achieved significantly higher phytomass in a more fertile environment in that they showed a high adaptability to environmental variation. Redtop and Kentucky bluegrass showed an increase in phytomass proportional to environmental improvement. The phytomass performances of perennial ryegrass and white clover were almost independent of environmental variation in that their adaptability was low. Finally, Zoysia japonica and weeds such as Pennisetum alopecuroides and Digitaria adscendens, which were invaders from the surrounding areas to the experimental site, were not observed in the pasture during the first 8-year period; during the second 8-year period, they showed moderate adaptability. [source] SCALES: a large-scale assessment model of soil erosion hazard in Basse-Normandie (northern-western France)EARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2010P. Le Gouée Abstract The cartography of erosion risk is mainly based on the development of models, which evaluate in a qualitative and quantitative manner the physical reproduction of the erosion processes (CORINE, EHU, INRA). These models are mainly semi-quantitative but can be physically based and spatially distributed (the Pan-European Soil Erosion Risk Assessment, PESERA). They are characterized by their simplicity and their applicability potential at large temporal and spatial scales. In developing our model SCALES (Spatialisation d'éChelle fine de l'ALéa Erosion des Sols/large-scale assessment and mapping model of soil erosion hazard), we had in mind several objectives: (1) to map soil erosion at a regional scale with the guarantee of a large accuracy on the local level, (2) to envisage an applicability of the model in European oceanic areas, (3) to focus the erosion hazard estimation on the level of source areas (on-site erosion), which are the agricultural parcels, (4) to take into account the weight of the temporality of agricultural practices (land-use concept). Because of these objectives, the nature of variables, which characterize the erosion factors and because of its structure, SCALES differs from other models. Tested in Basse-Normandie (Calvados 5500,km2) SCALES reveals a strong predisposition of the study area to the soil erosion which should require to be expressed in a wet year. Apart from an internal validation, we tried an intermediate one by comparing our results with those from INRA and PESERA. It appeared that these models under estimate medium erosion levels and differ in the spatial localization of areas with the highest erosion risks. SCALES underlines here the limitations in the use of pedo-transfer functions and the interpolation of input data with a low resolution. One must not forget however that these models are mainly focused on an interregional comparative approach. Therefore the comparison of SCALES data with those of the INRA and PESERA models cannot result on a convincing validation of our model. For the moment the validation is based on the opinion of local experts, who agree with the qualitative indications delivered by our cartography. An external validation of SCALES is foreseen, which will be based on a thorough inventory of erosion signals in areas with different hazard levels. Copyright © 2010 John Wiley & Sons, Ltd. [source] Comparative analysis of the widespread and conserved PB1-like viruses infecting Pseudomonas aeruginosaENVIRONMENTAL MICROBIOLOGY, Issue 11 2009Pieter-Jan Ceyssens Summary We examined the genetic diversity of lytic Pseudomonas aeruginosa bacteriophage PB1 and four closely related phages (LBL3, LMA2, 14-1 and SN) isolated throughout Europe. They all encapsulate linear, non-permuted genomes between 64 427 and 66 530 bp within a solid, acid-resistant isometric capsid (diameter: 74 nm) and carry non-flexible, contractile tails of approximately 140 nm. The genomes are organized into at least seven transcriptional blocks, alternating on both strands, and encode between 88 (LBL3) and 95 (LMA2) proteins. Their virion particles are composed of at least 22 different proteins, which were identified using mass spectrometry. Post-translational modifications were suggested for two proteins, and a frameshift hotspot was identified within ORF42, encoding a structural protein. Despite large temporal and spatial separations between phage isolations, very high sequence similarity and limited horizontal gene transfer were found between the individual viruses. These PB1-like viruses constitute a new genus of environmentally very widespread phages within the Myoviridae. [source] Contrasting responses of migration strategies in two European thrushes to climate changeGLOBAL CHANGE BIOLOGY, Issue 1 2007PHILIPPE RIVALAN Abstract Migration is a widespread strategy that enables animals to escape harsh winter conditions. It has been well documented that migration phenology in birds is changing in response to recent climate warming in the northern hemisphere. Despite the existence of large temporal and geographical scale ringing data on birds in Europe, changes in migration strategies in relation to climate warming have not been well studied, mainly because of a lack of appropriate statistical methods. In this paper, we develop a method that enables us to investigate temporal changes in migration strategies from recoveries of dead ringed birds. We estimated migration probability as the ratio between recovery probabilities of conspecific birds originating from different countries but potentially wintering in the same country. We applied this method to two European thrushes: the entirely migrant redwing Turdus iliacus, and the partially migrant blackbird T. merula. We tested for an immediate and a 1-year lagged relationship between our migration probability and climatic covariates (i.e. mean winter temperature in France and the North Atlantic Oscillation). Using ringing-recovery data collected in Finland, Germany, Switzerland and France from 1970 to 1999, we detected contrasting responses in these two species, likely related to their different migratory behaviours. Both species showed a decline in the probability for northern and eastern birds to winter in France. The entirely migratory redwing exhibited a year-to-year plastic response to climate, whereas the decline in the partially migrant blackbird was smooth, suggesting underlying genetic processes. The proposed method, thus, allows us to identify useful indicators of climatic impacts on migration strategies, as well as highlighting differences between closely related species. [source] Riparian influence on hyporheic-zone formation downstream of a small dam in the Blackland Prairie region of TexasHYDROLOGICAL PROCESSES, Issue 2 2007Jacquelyn R. Duke Abstract Small-order streams have highly variable flows that can result in large temporal and spatial variation of the hyporheic zone. Dam construction along these intermittent headwater streams alters downstream flow and influences the hydrologic balance between stream water and the adjacent riparian zone. A 3-year site study was conducted along an impounded second-order stream to determine the water balance between stream, unsaturated zone, groundwater and riparian vegetation. The presence of the upstream impoundment provided near-perennial water flow in the stream channel. The observed woody plant transpiration accounted for 71% of average annual water loss in the site. The overall contribution of stream water via the hyporheic zone to site water balance was 73 cm, or 44% of total inputs. This exceeded both rainfall and upland subsurface contribution to the site. A highly dynamic hyporheic zone was indicated by high water use from woody plants that fluctuated seasonally with stream water levels. We found leaf area development in the canopy layer to be closely coupled with stream and groundwater fluctuations, indicating its usefulness as a potential indicator of site water balance for small dam systems. The net result of upstream impoundment increased riparian vegetation productivity by influencing movement of stream water to storage in the groundwater system. Copyright © 2006 John Wiley & Sons, Ltd. [source] Evaluating the power of monitoring plot designs for detecting long-term trends in the numbers of common guillemotsJOURNAL OF APPLIED ECOLOGY, Issue 3 2006MICHELLE SIMS Summary 1In recent years concerns have been raised regarding the status of the common guillemot Uria aalge in the UK. Numbers have declined in several regions, highlighting the need for continued monitoring of this internationally important population. However, the extent to which the current monitoring scheme is capable of detecting declines and options for improving efficiency has received little attention. 2We investigated the power of different monitoring design options for detecting long-term trends in abundance at a colony of guillemots. The ability to detect trends in abundance was reduced by the large temporal and spatial variability in colony attendance. Taking a linear mixed model approach, we obtained details on the sources and sizes of the variance components using count data collected from monitoring plots on the Isle of May, Scotland, and assessed how best to allocate sampling effort in the light of the count variability structure. 3Our results indicated that trend detection will be improved by counting birds in more plots rather than by increasing the number of counts at existing plots. 4The revisit pattern of counts at the monitoring plots during the seasonal counting period had little effect on trend detection power. However, given the practical issues associated with counting guillemots, alternative revisit patterns to the current approach are preferred. 5For a fixed number of visits per plot, power is strongly influenced by the choice of revisit design if the day-to-day variation in colony attendance is increased. 6Synthesis and applications. Aspects of the UK seabird monitoring scheme can be improved. Changes to the allocation of sampling effort and the plot-revisit pattern will improve both the statistical power to detect long-term trends and the efficiency of conducting the survey. We stress the importance of considering the structure and magnitude of the count variation in a power analysis because judicious design decisions depend on the relative magnitude of these variance components. [source] Risk assessment methodologies for predicting phosphorus losses,JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 4 2003Oscar F. Schoumans Abstract Risk assessment parameters are needed to assess the contribution of phosphorus (P) losses from soil to surface water, and the effectiveness of nutrient and land management strategies for the reduction of P loss. These parameters need to take into account the large temporal and spatial variation in P transfer from individual fields arising from (a) changing but predictable factors such as land use, soil P status, P application rates, forms and ways of fertilization and spreading, (b) predictable but inherent factors such as soil type, soil dispersivity, slope and hydrological routing, and (c) unpredictable weather factors such as rainfall amount and intensity. In most situations, water transport is the driving force of P loss from agricultural land to surface water. Therefore, the hydrological pathways determine to a large extent the relevance of these different factors. Over the last decade several soil P tests have been proposed as a first step to link field conditions to risk of P loss. The major reason is that these soil P tests are also meaningful in discussions with farmers. Recently, more complex P loss risk parameters have been derived based on different approaches. However, the scope and purposes of these P loss risk parameters vary remarkably. Finally, there is a need to evaluate the usefulness of new P tests that can be used as an indicator of P loss risk, e.g. in relation to monitoring purposes. The implementation of the EU Water Framework Directive will increase this need. In this paper, the practicable applicability of P parameters for risk assessment is discussed in relation to purpose, scale (from field, farm to catchment), effectiveness, sensibility etc. Furthermore, a conceptual framework for P indicators is presented and evaluated, based on the outcome of the presentations and the discussions in Zurich. No translation. [source] Using phylochronology to reveal cryptic population histories: review and synthesis of 29 ancient DNA studiesMOLECULAR ECOLOGY, Issue 7 2009UMA RAMAKRISHNAN Abstract The evolutionary history of a population involves changes in size, movements and selection pressures through time. Reconstruction of population history based on modern genetic data tends to be averaged over time or to be biased by generally reflecting only recent or extreme events, leaving many population historic processes undetected. Temporal genetic data present opportunities to reveal more complex population histories and provide important insights into what processes have influenced modern genetic diversity. Here we provide a synopsis of methods available for the analysis of ancient genetic data. We review 29 ancient DNA studies, summarizing the analytical methods and general conclusions for each study. Using the serial coalescent and a model-testing approach, we then re-analyse data from two species represented by these data sets in a common interpretive framework. Our analyses show that phylochronologic data can reveal more about population history than modern data alone, thus revealing ,cryptic' population processes, and enable us to determine whether simple or complex models best explain the data. Our re-analyses point to the need for novel methods that consider gene flow, multiple populations and population size in reconstruction of population history. We conclude that population genetic samples over large temporal and geographical scales, when analysed using more complex models and the serial coalescent, are critical to understand past population dynamics and provide important tools for reconstructing the evolutionary process. [source] Nonequilibrium quantum anharmonic oscillator and scalar field: high temperature approximationsANNALEN DER PHYSIK, Issue 6 2009R.F. Alvarez-Estrada Abstract We treat a relativistic quantum boson gas, described by a scalar quantum field, with quartic self-interaction (,4) in three spatial dimensions: we review the known equilibrium case and present new proposals off-equilibrium. For high temperature and large spatial scales, the behaviour of the gas at equilibrium simplifies nonperturbatively (equilibrium dimensional reduction or EDR): its thermodynamics is described by classical statistical mechanics with some quantum field effects. By assumption, the initial state of the gas off-equilibrium includes interactions and inhomogeneities and is not far from thermal equilibrium. We employ real-time generating functionals and obtain the free nonequilibrium correlators at non-zero temperature. The nonequilibrium quantum gas appears to simplify nonperturbatively in the regime of high temperature and large temporal and spatial scales (nonequilibrium dimensional reduction or NEDR), its dynamics being described by classical statistical mechanics with some quantum field effects. We outline the renormalization of the ,4 theory, the nonequilibrium statistical mechanics of a quantum anharmonic oscillator and the high temperature simplifications, all of which provide very useful hints for NEDR in the field case. Our main proposals are NEDR and the associated new (renormalized) real-time nonequilibrium generating functionals for the ,4 theory. [source] | |||||||||||||