Search results for "Stable state"
showing 10 items of 21 documents
From clear lakes to murky waters – tracing the functional response of high-latitude lake communities to concurrent ‘greening’ and ‘browning’
2019
Climate change and the intensification of land use practices are causing widespread eutrophication of subarctic lakes. The implications of this rapid change for lake ecosystem function remain poorly understood. To assess how freshwater communities respond to such profound changes in their habitat and resource availability, we conducted a space-for-time analysis of food-web structure in 30 lakes situated across a temperature-productivity gradient equivalent to the predicted future climate of subarctic Europe (temperature +3 degrees C, precipitation +30% and nutrient +45 mu g L-1 total phosphorus). Along this gradient, we observed an increase in the assimilation of pelagic-derived carbon from…
Macroalgal forest vs sea urchin barren: Patterns of macro-zoobenthic diversity in a large-scale Mediterranean study.
2019
Abstract The study aimed at contributing to the knowledge of alternative stable states by evaluating the differences of mobile and sessile macro-zoobenthic assemblages between sea urchin barrens and macroalgal forests in coastal Mediterranean systems considering a large spatial scale. Six sites (100 s km apart) were selected: Croatia, Montenegro, Sicily (Italy), Sardinia (Italy), Tuscany (Italy), and Balearic Islands (Spain). A total of 531 taxa, 404 mobile and 127 sessile macro-invertebrates were recorded. Overall, 496 and 201 taxa were found in macroalgal forests and in barrens, respectively. The results of this large-scale descriptive study have met the expectation of lower macrofauna co…
Micropredation on sea urchins as a potential stabilizing process for rocky reefs
2012
Rocky reefs can shift from forest, a state dominated by erect algae with high biodiversity, to barren, an impoverished state dominated by encrusting algae. Sea urchins, abundant in barrens, are usually held responsible for the maintenance of this state. Predation by large fish can revert the barren state to forest by controlling sea urchin populations. However, the persistence of a community state sometimes seems to be independent from the presence of such large predators, suggesting the existence of other, unknown mechanisms ensuring their stability. Theoretical studies suggest that the settler stage of sea urchins is determinant for maintaining a given rocky reef state. In this study, we …
Continental-scale patterns of nutrient and fish effects on shallow lakes: synthesis of a pan-European mesocosm experiment
2004
1. Results are analysed from 11 experiments in which effects of fish addition and nutrient loading on shallow lakes were studied in mesocosms. The experiments, five in 1998, six in 1999, were carried out in six lakes, distributed from Finland to southern Spain, according to a standard protocol. 2. Effects of the treatments on 29 standard chemical, phytoplankton and zooplankton variables are examined to assess the relative importance of bottom-up (nutrient enrichment) and top-down (fish predation) effects. For each year, the experiments in different locations are treated as replicates in a meta-analysis. Results of individual experiments are then compared in terms of the patterns of signific…
Synthetic biology: Engineered stable ecosystems
2017
International audience; Co-culture of bacterial cells engineered with quorum-sensing and self-lysis circuits allows coupled oscillatory dynamics and stable states, opening the way to engineered microbial ecosystems with targeted dynamics and extending gene circuits to the ecosystem level.
Simulations and Experiments in Protein Folding
2014
The interplay between simulations and experiments of protein folding has largely contributed to the elucidation of many important aspects of the phenomenon. In this chapter, I briefly describe the experiments which provide information on the kinetics of the protein folding process, and help to characterize the folding transition state. Then, I show how to probe the kinetics of protein folding using molecular dynamics simulations, how to compare the simulations with the experiments and how to help and rationalize the latter, ultimately offering a molecular picture of the process. After the production of suitable molecular dynamics simulation data in the form of trajectories, the procedure in…
Regime shifts and alternative stable states in intertidal rocky habitats: State of the art and new trends of research
2018
Abstract The existence of regime shifts and alternative stable states in ecosystems is well known and has very large effects on their structure and dynamics. Since shifts between alternative stable states have significant implications for the ecosystems conservation, their prevention should be an aim of primary interest, and for this reason a particular attention has been paid to their study. Regarding marine ecosystems, rocky intertidal habitats, in particular, represent an ideal system for the study of alternative stable states because of their characteristics: they exhibit strong environmental gradients, are easy to manipulate, and most of the inhabiting species grow rapidly. Given the s…
Phase dynamics in graphene-based Josephson junctions in the presence of thermal and correlated fluctuations
2014
In this work we study by numerical methods the phase dynamics in ballistic graphene-based short Josephson junctions. The supercurrent through a graphene junction shows a non-sinusoidal phase-dependence, unlike a conventional junction ruled by the well-known d.c. Josephson relation. A superconductor-graphene-superconductor system exhibits superconductive quantum metastable states similar to those present in normal current-biased JJs. We explore the effects of thermal and correlated fluctuations on the escape time from these metastable states, when the system is stimulated by an oscillating bias current. As a first step, the analysis is carried out in the presence of an external Gaussian whit…
Dynamics in stochastic evolutionary models
2016
We characterize transitions between stochastically stable states and relative ergodic probabilities in the theory of the evolution of conventions. We give an application to the fall of hegemonies in the evolutionary theory of institutions and conflict, and illustrate the theory with the fall of the Qing dynasty and the rise of communism in China.
The bistable system: an archetypal model for complex systems
2011
Bistable systems often play the role of archetypal models to understand the dynamical behavior of complex systems. Examples range from microphysics to macrophysics, bìology, chemistry and also econophysics. Moreover the statistical mechanics is essential to study the physical properties of complex systems and to investigate stochastic systems in which the microscopic degrees of freedom behave collectively over large scales. We investigate the nonlinear relaxation in a bistable system in classical and quantum systems. (i) As a first classical system, the role of the multiplicative and additive noise in the mean life time of the metastable state of an asymmetric bistable system is investigate…