Search results for "feature"
showing 10 items of 4091 documents
Controlling factors of phytoplankton assemblages in wetlands: an experimental approach
2003
The aim of this work is to answer some questions like: what factors control the phytoplankton assemblage? What factor or factors are perturbing the assemblage? What factors are driving or maintaining the stability? Are the different responses to the control factors dependent on the hierarchy level? For that, we tested experimentally the influence of herbivory, planktivory, nutrients and sediment on phytoplankton assemblages and its stability from a hypertrophic wetland (Las Tablas de Daimiel National Park, Spain) in three microcosm experiments. The study of the steady state phytoplankton assemblages in this perturbed system could point out some underlying processes instead of competition. T…
Many More Consumers Not Always Induce Stronger Competition: Weaker Interspecific Competition Despite Higher Species Richness in Secondary Feeding Gui…
2021
The species functional structuration (specifically in terms of species richness and average intensity of interspecific competition) is widely varying among species communities and this point is now very well documented in literature. But, what about the species functional structuration within the different feeding guilds that coexist in a same local community – in particular the primary and the secondary feeding guilds? Are there significant differences – or not – between them in this respect? This rather fundamental issue does not seem having been addressed yet, at least using appropriate investigative tools. However, a series of recently published case studies, precisely implementing such…
Changes in alpine snowbed-wetland vegetation over three decades in northern Norway
2013
We have quantified floristic changes in alpine snowbeds and wetland vegetation during three decades and analyzed to what extent these changes are related to initial variations in snow cover duration and distance to groundwater level. Vascular plant species richness and total plant cover were estimated along three transects in northern Norway. Three different vegetation zones were identified along the original transects: relatively dry snowbeds, wet snowbeds and wetlands. The resampling shows major changes in species richness and plant cover. In general, there was a net immigration of species and 13 new species were found. Five rare species with initial low cover were lost. In the dry and we…
Analysis of Conflict Datasets and Indicators: The Case of the “Arab Spring”
2017
This chapter contains an analysis of selected indicators of legitimacy, human rights and inequality, as well as information about conflict events for eight African countries affected by the Arab Spring, namely Algeria, Egypt, Libya, Mali, Mauritania, Morocco, Sudan, and Tunisia. The analyses described in this chapter allowed the determination of plausible estimates for input parameters such as legitimacy and welfare inequality, as well as patterns of size, duration and recurrence of conflict events in these countries. These results were used for setting the values of the input parameters, and for analyzing the plausibility of the solutions in the exploration of the agent-based model describ…
South China Sea or West Philippine Sea?
2017
The South China Sea (“West Philippine Sea”) has been for several years a space of potential conflict between several countries due to overlapping of their EEZs and China’s claim of a large part of this oceanic space, well beyond its UN-endorsed EEZ. The Spratly islets and Scarborough shoal are mere coral reefs, uninhabited for the most part, but they lie in the middle of rich fishing grounds and atop large reserves of petroleum and natural gas. Furthermore, the area is one of the world’s busiest sea lanes for commercial navigation. This chapter presents the general rules of UNCLOS (international laws pertaining to oceanic space), and then examines the competing claims, focusing on the China…
Vertical distribution and rotifer concentrations in the chemocline of meromictic lakes
1983
The vertical distribution of planktonic rotifers has been analysed in relation to season in several meromictic lakes; a coastal lagoon with sea-water intrusion and three dissolution lakes from two karstic systems. Two species, Filinia hofmanni and a form of Anuraeopsis fissa have been found to be more or less restricted to the chemocline or adjacent strata any time they occurred. Many species common in the upper water layers developed large populations near or in the chemocline and more strikingly in summer. Some species had two vertical maxima (one in the surface or the thermocline and another near the chemocline), while others successively shifted their maxima between the upper layers and…
Rapid conversion of elastic energy into plastic shear heating during incipient necking of the lithosphere
1998
An important and novel mechanism for ductile failure of the lithosphere is identified here, which is intrinsic to the thermal-mechanical feedback in a temperature dependent plastic body with coupled elastic fields. Both a temperature-dependent power-law visco-elasto-plastic rheology and a temperature-dependent elasto-plastic rheology are employed to study in a self-consistent fashion the deformation of the lithosphere subject to extension by means of a two-dimensional, finite-element code. A structural perturbation initially localizes elasto-plastic deformation only in its immediate vicinity. However, after 800,000 years have elapsed the localized zone of deformation takes off in a ‘crack-l…
The Body Size of Headstarted and Wild Juvenile European Pond Turtles (<i>Emys orbicularis</i>)
2017
Headstarting is a popular conservation technique in which animals are raised under artificial conditions, and then released into natural habitat. The objective of this procedure is to grow animals to a size at which they are less vulnerable to predators. However, there is still little empirical evidence for the long-term effectiveness of the technique. Therefore, we compared body size of juvenile «wild» (= not taken to artificial rearing) and headstarted European pond turtles ( Emys orbicularis ), from two populations (in central and western Poland). Immediately after hatching there were no differences in size of the turtles, but after seven-ten years headstarted turtles were smaller. This …
Evidence from zircon dating for existence of approximately 2.1 Ga old crystalline basement in southern Bohemia, Czech Republic
1993
Zircon ages are reported for three Moldanubian amphibolite grade orthogneisses from the southern Bohemian Massif obtained by conventional U/Pb analyses. For two of these orthogneisses, conventional U/Pb data are supported by ion microprobe single zircon ages or single grain evaporation data. The amphibolite grade orthogneisses, occurring in three small tectonic lenses within the Varied Group close to the South Bohemian Main Thrust, are of tonalitic, granodioritic or quartz dioritic composition.
3D Numerical Modelling of Salt Tectonics
2017
Summary Many factors have been suggested to affect the development of salt structures, including sedimentation, brittle sediment deformation, multiple tectonic events and basement topography. To unravel the relative importance of these processes, we performed high resolution 2D and 3D thermo-mechanical simulations that take these factors into account, while incorporating nonlinear salt creep laws and visco-elasto-plastic rock properties. Simulations show that the sedimentation rate affects both the speed with which structures form, and the spacing between the salt structures, which is larger for higher rates. Consistent with earlier sandbox experiments, we find that there is a feedback betw…