Littérature scientifique sur le sujet « Ecosystem perturbation »
Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres
Sommaire
Consultez les listes thématiques d’articles de revues, de livres, de thèses, de rapports de conférences et d’autres sources académiques sur le sujet « Ecosystem perturbation ».
À côté de chaque source dans la liste de références il y a un bouton « Ajouter à la bibliographie ». Cliquez sur ce bouton, et nous générerons automatiquement la référence bibliographique pour la source choisie selon votre style de citation préféré : APA, MLA, Harvard, Vancouver, Chicago, etc.
Vous pouvez aussi télécharger le texte intégral de la publication scolaire au format pdf et consulter son résumé en ligne lorsque ces informations sont inclues dans les métadonnées.
Articles de revues sur le sujet "Ecosystem perturbation"
1
Harvey, Eric, Isabelle Gounand, Pravin Ganesanandamoorthy et Florian Altermatt. « Spatially cascading effect of perturbations in experimental meta-ecosystems ». Proceedings of the Royal Society B : Biological Sciences 283, no 1838 (14 septembre 2016) : 20161496. http://dx.doi.org/10.1098/rspb.2016.1496.
Texte intégralRésumé :
Ecosystems are linked to neighbouring ecosystems not only by dispersal, but also by the movement of subsidy. Such subsidy couplings between ecosystems have important landscape-scale implications because perturbations in one ecosystem may affect community structure and functioning in neighbouring ecosystems via increased/decreased subsidies. Here, we combine a general theoretical approach based on harvesting theory and a two-patch protist meta-ecosystem experiment to test the effect of regional perturbations on local community dynamics. We first characterized the relationship between the perturbation regime and local population demography on detritus production using a mathematical model. We then experimentally simulated a perturbation gradient affecting connected ecosystems simultaneously, thus altering cross-ecosystem subsidy exchanges. We demonstrate that the perturbation regime can interact with local population dynamics to trigger unexpected temporal variations in subsidy pulses from one ecosystem to another. High perturbation intensity initially led to the highest level of subsidy flows; however, the level of perturbation interacted with population dynamics to generate a crash in subsidy exchange over time. Both theoretical and experimental results show that a perturbation regime interacting with local community dynamics can induce a collapse in population levels for recipient ecosystems. These results call for integrative management of human-altered landscapes that takes into account regional dynamics of both species and resource flows.
2
Sun, G., et M. Mu. « Nonlinearly combined impacts of initial perturbation from human activities and parameter perturbation from climate change on the grassland ecosystem ». Nonlinear Processes in Geophysics 18, no 6 (29 novembre 2011) : 883–93. http://dx.doi.org/10.5194/npg-18-883-2011.
Texte intégralRésumé :
Abstract. Human activities and climate change are important factors that affect grassland ecosystems. A new optimization approach, the approach of conditional nonlinear optimal perturbation (CNOP) related to initial and parameter perturbations, is employed to explore the nonlinearly combined impacts of human activities and climate change on a grassland ecosystem using a theoretical grassland model. In our study, it is assumed that the initial perturbations and parameter perturbations are regarded as human activities and climate change, respectively. Numerical results indicate that the climate changes causing the maximum effect in the grassland ecosystem are different under disparate intensities of human activities. This implies the pattern of climate change is very critical to the maintenance or degradation of grassland ecosystem in light of high intensity of human activities and that the grassland ecosystem should be rationally managed when the moisture index decreases. The grassland ecosystem influenced by the nonlinear combination of human activities and climate change undergoes abrupt change, while the grassland ecosystem affected by other types of human activities and climate change fails to show the abrupt change under a certain range of perturbations with the theoretical model. The further numerical analyses also indicate that the growth of living biomass and the evaporation from soil surface shaded by the wilted biomass may be crucial factors contributing to the abrupt change of the grassland equilibrium state within the theoretical model.
3
Wang, Bo, Zhen Hua Huo, Qian Qian Qi et Pei Jun Zhang. « The Research on the Lake Eutrophication with CNOP Method ». Advanced Materials Research 599 (novembre 2012) : 705–8. http://dx.doi.org/10.4028/www.scientific.net/amr.599.705.
Texte intégralRésumé :
Using a dynamical model for nutrient cycling in shallow lakes, the approach of conditional nonlinear optimal perturbation (CNOP) was adopted to investigate the instability and the sensitivity of the lake ecosystem to finite-amplitude perturbations both related to the initial condition and the parameter. The results show that the ecosystem can be transformed from an oligotrophic (eutrophic) state to an eutrophic (oligotrophic) state with a CNOP as the perturbation, no matter how large the nutrient loading rate is. Above all, with the same restraints related to the initial perturbation and the parameter perturbation, CNOP has the largest effect on the lake ecosystem, which may be helpful to govern the lake ecosystem.
4
Jia, Wantao, Yong Xu, Dongxi Li et Rongchun Hu. « Stochastic Analysis of Predator–Prey Models under Combined Gaussian and Poisson White Noise via Stochastic Averaging Method ». Entropy 23, no 9 (13 septembre 2021) : 1208. http://dx.doi.org/10.3390/e23091208.
Texte intégralRésumé :
In the present paper, the statistical responses of two-special prey–predator type ecosystem models excited by combined Gaussian and Poisson white noise are investigated by generalizing the stochastic averaging method. First, we unify the deterministic models for the two cases where preys are abundant and the predator population is large, respectively. Then, under some natural assumptions of small perturbations and system parameters, the stochastic models are introduced. The stochastic averaging method is generalized to compute the statistical responses described by stationary probability density functions (PDFs) and moments for population densities in the ecosystems using a perturbation technique. Based on these statistical responses, the effects of ecosystem parameters and the noise parameters on the stationary PDFs and moments are discussed. Additionally, we also calculate the Gaussian approximate solution to illustrate the effectiveness of the perturbation results. The results show that the larger the mean arrival rate, the smaller the difference between the perturbation solution and Gaussian approximation solution. In addition, direct Monte Carlo simulation is performed to validate the above results.
5
Wang, Bo, Peijun Zhang, Zhenhua Huo et Qianqian Qi. « The Sensitivity Analysis of a Lake Ecosystem with the Conditional Nonlinear Optimal Perturbation Method ». Advances in Meteorology 2012 (2012) : 1–7. http://dx.doi.org/10.1155/2012/562081.
Texte intégralRésumé :
The instability and sensitivity of a lake ecosystem to the finite-amplitude perturbations related to the initial condition and the parameter correspondingly are studied. The CNOP-I and CNOP-P methods are adopted to investigate this nonlinear system. The numerical results with CNOP-I method show that the lake ecosystem can be nonlinearly unstable with finite-amplitude initial perturbations when the nutrient loading rate is between the two bifurcation points. A large enough finite amplitude initial perturbation, that is, CNOP-I, can induce a transition from an oligotrophic (eutrophic) state to an eutrophic (oligotrophic) state. With CNOP-P method, it is shown that the lake ecosystem can be transformed from an oligotrophic (eutrophic) state to an eutrophic (oligotrophic) state with a large enough finite amplitude parameter perturbation, that is, CNOP-P, no matter how large the nutrient loading rate is.
6
Healey, Katherine, Adam H. Monahan et Debby Ianson. « Perturbation dynamics of a planktonic ecosystem ». Journal of Marine Research 67, no 5 (1 septembre 2009) : 637–66. http://dx.doi.org/10.1357/002224009791218841.
Texte intégral
7
Equihua, Miguel, Mariana Espinosa Aldama, Carlos Gershenson, Oliver López-Corona, Mariana Munguía, Octavio Pérez-Maqueo et Elvia Ramírez-Carrillo. « Ecosystem antifragility : beyond integrity and resilience ». PeerJ 8 (11 février 2020) : e8533. http://dx.doi.org/10.7717/peerj.8533.
Texte intégralRésumé :
We review the concept of ecosystem resilience in its relation to ecosystem integrity from an information theory approach. We summarize the literature on the subject identifying three main narratives: ecosystem properties that enable them to be more resilient; ecosystem response to perturbations; and complexity. We also include original ideas with theoretical and quantitative developments with application examples. The main contribution is a new way to rethink resilience, that is mathematically formal and easy to evaluate heuristically in real-world applications: ecosystem antifragility. An ecosystem is antifragile if it benefits from environmental variability. Antifragility therefore goes beyond robustness or resilience because while resilient/robust systems are merely perturbation-resistant, antifragile structures not only withstand stress but also benefit from it.
8
Al-Habahbeh, Amalia Keck, Susanne Kortsch, Bodil A. Bluhm, Frank Beuchel, Bjørn Gulliksen, Carl Ballantine, Domiziana Cristini et Raul Primicerio. « Arctic coastal benthos long-term responses to perturbations under climate warming ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 378, no 2181 (31 août 2020) : 20190355. http://dx.doi.org/10.1098/rsta.2019.0355.
Texte intégralRésumé :
Climate warming influences structure and function of Arctic benthic ecosystems. Assessing the response of these systems to perturbations requires long-term studies addressing key ecological processes related to recolonization and succession of species. Based on unique time-series (1980–2017), this study addresses successional patterns of hard-bottom benthos in two fjords in NW Svalbard after a pulse perturbation in 1980 and during a period of rapid climate warming. Analysis of seafloor photographs revealed different return rates of taxa, and variability in species densities, through time. It took 13 and 24 years for the community compositions of cleared and control transects to converge in the two fjords. Nearly two decades after the study initiation, an increase in filamentous and foliose macroalgae was observed with a subsequent reorganization in the invertebrate community. Trait analyses showed a decrease in body size and longevity of taxa in response to the pulse perturbation and a shift towards small/medium size and intermediate longevity following the macroalgae takeover. The observed slow recovery rates and abrupt shifts in community structure document the vulnerability of Arctic coastal ecosystems to perturbations and continued effects of climate warming. This article is part of the theme issue ‘The changing Arctic Ocean: consequences for biological communities, biogeochemical processes and ecosystem functioning’.
9
Straškraba, M. « Terrestrial and aquatic ecosystem. Perturbation and recovery ». Ecological Modelling 64, no 1 (octobre 1992) : 77–79. http://dx.doi.org/10.1016/0304-3800(92)90052-g.
Texte intégral
10
Mu, M., et B. Wang. « Nonlinear instability and sensitivity of a theoretical grassland ecosystem to finite-amplitude perturbations ». Nonlinear Processes in Geophysics 14, no 4 (19 juillet 2007) : 409–23. http://dx.doi.org/10.5194/npg-14-409-2007.
Texte intégralRésumé :
Abstract. Within a theoretical model context, the sensitivity and instability of the grassland ecosystem to finite-amplitude perturbations are studied. A new approach of conditional nonlinear optimal perturbations (CNOPs) is adopted to investigate this nonlinear problem. It is shown that the linearly stable grassland (desert) states can be nonlinearly unstable with finite-amplitude initial perturbations, which represent the human activities and natural factors on the ecosystem. When the moisture index is between the two bifurcation points, a large enough finite amplitude perturbation can induce a transition from the grassland (desert) state to the desert (grassland) state. The thresholds of such transition along the bifurcation diagram of the moisture index are also given by the CNOPs approach. The results also support the viewpoint of Zeng et al., whose emphasis is on the shading effect of wilted grass on the grassland ecosystem. Comparisons between the results obtained by approach of CNOPs and linear singular vectors are made, which demonstrates that CNOPs is a useful tool to explore the nonlinear features of the ecosystem.
Thèses sur le sujet "Ecosystem perturbation"
1
Roy, Eric Daniel. « Modeling Interactions Between Environmental Management and Ecosystem Services in a Dynamic Freshwater Ecosystem ». The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1218487995.
Texte intégral
2
Peter, Hannes. « Diversity and Ecosystem Functioning : Redundancy and Resilience in Freshwater Bacterial Communities ». Doctoral thesis, Uppsala universitet, Limnologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-160780.
Texte intégralRésumé :
Bacteria are immensely diverse and hold key-positions in essentially all biogeochemical cycles. In freshwater ecosystems, bacteria degrade and mineralize organic compounds, linking the pool of dissolved organic matter to higher trophic levels. Aware of the global biodiversity loss, ecologists have started identifying the relationship of diversity and ecosystem functioning. Central to this is the question if species can functionally replace other species, hence being functionally redundant. Functional redundancy might allow communities to maintain functioning when diversity is lost. Due to their large numbers and great diversity, bacterial communities have been suspected to harbor large amounts of redundancy. The central aim of this thesis is to investigate the coupling of diversity and ecosystem functioning of bacterial communities and to understand how environmental perturbation affects this relationship. I manipulated the diversity of complex communities by a dilution technique, and measured the performance of bacterioplankton and biofilm-forming communities at different diversities. Reduction of bacterial diversity differently affected different functions, and that the presence or absence of certain species might be causing this pattern. However, for ecosystems to function, the interplay of multiple functions, i.e. multifunctionality, has to be sustained over long periods of time. In bacterial biofilm communities reduced diversity affected multifunctionality, as reflected by extracellular enzyme activities. A continuous cultivation system was used to address the importance of diversity for resistance and resilience upon environmental perturbation. The analysis of co-occurrence of bacterial taxa showed that the communities form a dense network before the perturbation and that these patterns are disturbed by the environmental perturbation. The final chapter of the thesis presents experimental evidence for the positive effects of temporal and spatial refuges for bacterial communities and the functions they provide. Overall, I found several indications for a lower amount of functional redundancy as previously assumed and it becomes apparent from this thesis that a multifunctional perspective and the consideration of environmental heterogeneity is pivotal.
3
Zha, Yinghua. « Effects of diversity and dispersal on the response of bacterial community to starvation perturbation ». Thesis, Uppsala universitet, Limnologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-166049.
Texte intégralRésumé :
Bacterial diversity and ecosystem functioning (BEF) relationships have received considerable attention during the last three decades and tend to be positive in most cases. However, most studies were done in closed systems and largely ignored the importance of placing local communities into the metacommunity context, in which dispersal can be a crucial factor modifying community diversity and composition and ecosystem functioning. The aim of this study was to investigate the effects of both diversity and dispersal on the responses of bacterial community to a starvation perturbation. To achieve this, we implemented a batch culture experiment using the dilution-to-extinction approach to create a diversity gradient of local bacterial community richness. Different dispersal rates were manipulated by transferring cells in different quantities from a regional source to the cultures, and they were then exposed to a perturbation by transferring them into water from another lake which differed in organic carbon content and quality. We evaluated the BEF relationship by measuring the bacterial community composition using t-RFLP and multiple ecosystem functions. Generally, our results demonstrated that diversity and dispersal have an interactive and positive effect on ecosystem functioning. In particular, dispersal had a stronger and more pronounced effect on ecosystem functioning when bacterial diversity was low. When evaluating the responses of bacterial community respiration, no significant difference was observed among different treatments, however, there were clear differences in substrate utilization patterns, implying that specific functions, such as decomposing certain substrates, are more sensitive to a perturbation than general functions, such as respiration. Therefore it is important to include multiple functional parameters when studying BEF relationships and, in particular, when applying our knowledge to the conservation of natural environments.
4
Corradini, Andrea. « Ecological connectivity in the Alpine anthropic matrix. Natural reserves and corridors for the conservation of brown bear in the Alps (ABC - AlpBearConnect) ». Doctoral thesis, Università degli studi di Trento, 2021. http://hdl.handle.net/11572/321014.
Texte intégralRésumé :
Large carnivores are among the most challenging species to conserve in our modern and crowded world. Having large spatial requirements and living in low density, they generally require wide and relatively undisturbed areas. In Europe, one of the most anthropized areas of the planet, these needs must be fulfilled in a complex human-dominated landscape. The reintroduced brown bear population living in the Central Alps represents one of the most emblematic examples of a constrained carnivore: despite a steady population increase in the first few years after reintroduction, the population did not substantially expand its range, nor has the Alpine-Dinaric metapopulation been reestablished as envisioned. Although humans have lived in the Alps for centuries, little is known about their impact on the bear population. In other environments humans are known to function as a “super-predator” by changing habitats, competing for space, consuming resources, and harvesting, which alters the ecological niche of animals, especially large carnivores. This dissertation aims to evaluate this phenomenon by assessing the effects of human disturbance on brown bears in the Alps. Anthropogenic disturbance is generally assessed by structural proxies, such as infrastructure and land use, which overlook the impact of human presence. In the first Chapter, we developed the Cumulative Outdoor activity Index (COI) to derive anthropogenic disturbance using crowdsourced data by Strava and validated it with ground truth observations derived from a local camera trapping survey. The intensity of COI provided an effective measure of functional anthropogenic disturbance, and it outperformed all commonly-used proxies of structural disturbance in predicting bear habitat use. When displacement is not an option because of habitat limitations and social mechanisms, bear mobility may clash with human activity. During the moments of lowest mobility, such as resting periods, animals have decreased ability to cope with risky situations, and therefore the selection of suitable resting areas is crucial for the long-term survival of individuals. In the second Chapter, we measured multi-scale response to risk perception (i.e., COI) and resource proximity using bedding sites by GPS radio-collared adult brown bears in the Alps. To map resources across the study area, we developed a GIS-database combining spatial and non-spatial ecological information to map fruit availability. We observed that bears apply a security-food trade-off strategy, avoiding functional anthropogenic disturbance while in proximity to resources. In the third Chapter, we explicitly tested the effect of an abrupt interruption of human mobility during COVID-19 lockdown on bears’ use of ecological corridors. Using bear occurrences reported to local authorities during the recent COVID-19 outbreak, we observed that bears used human-dominated areas more frequently, approached more intensively hot spots for road crossing network, and used areas further from the population core areas more often than previous years, suggesting that connectivity increased with reduced human mobility. In a comparatively human-free system, for the fourth Chapter we used longitudinal morphometric data to analyze drivers of changes in body mass as part of an international collaboration with biologists studying the grizzly bear in the Greater Yellowstone Ecosystem. Specifically, we analyzed changes in lean body mass and fat percentage during years of major ecosystem perturbations. We observed that individual lean body mass during the last two decades was primarily associated with population density, but not body fat percentage, showing density-dependent factors. Our combined findings (Chapters 1-3) showed that brown bears have to adapt their space use, movement, and resource proximity as a result of functional anthropogenic disturbance. In Chapter 4 we explored one effect of unconstrained bear space use on individuals, as manifested through density-dependent effects on body size. In the Alps, however, we found multiple instances of the human-super predator outcompeting bears so as to make density-dependent effects likely less significant as compared to human-caused mortality. These effects could occur in a variety of socio-ecological contexts across Europe, jeopardizing the long-term establishment of both newly reintroduced bear populations, as well as spatially limiting those naturally present in the environment. In response to disturbance, bears have had to reduce their ecological niche in human-dominated landscapes. Allowing humans and bears to coexist in the same landscape is a challenging task, but it is essential for the long-term survival of this newly reintroduced population that are otherwise at risk of extinction.
5
ROCCHI, Marta. « Ecosystem response to perturbations : insight from qualitative analysis ». Doctoral thesis, Università degli studi di Ferrara, 2017. http://hdl.handle.net/11392/2488077.
Texte intégralRésumé :
Present changing environment calls for improvements of our knowledge of natural systems structure and function through a holistic view. Such a whole system perspective might help to better understand responses of ecosystems to perturbations. Models of ecological networks have proven to be very useful tools for understanding structure, and dynamics of ecosystems. I am presenting two modelling techniques to deal with the whole system approach: topological food web analysis (chapter 2) and loop analysis (chapter 3 and 4). Both these studies privilege the qualitative analysis over the quantitative one, to overcome the lack of data.
In chapter 2 the topology of the food web is considered to study the functioning of the Baja California Sur ecosystem. I identified through centrality indices key node species and analyzed system resilience to the removal of the most vulnerable fish species based on a previous classification of high, medium and low risk species. Effects are evaluated by using global indices. Results highlight the structural resilience of the web to removals, but also that removals of highly vulnerable species result in significant changes in system attributes compared to random removal.
In chapter 3 the evolution of the Black Sea ecosystem during the period 1960-1990 is evaluated through qualitative models (i.e. loop analysis). These models reconstruct the linkage structure of the whole community. I validated the outcomes of loop analysis with statistical investigation of biomass time series. This helped to understand how the structure of the interactions can explain variations in the biomass level of the variables and what hypotheses about drivers and mechanisms responsible for the changes could be shaped accordingly.
In chapter 4 a database of real and random food webs was taken into account. I studied these food webs through loop analysis to unveil how positive input on basal and top species affects top and basal species, respectively. The aim was to identify possible differences in the propagation of indirect impacts in response to positive perturbations that occur at the extreme of the food webs (i.e. either targeting basal or top species). I compared real systems (i.e. marine, terrestrial and freshwater food webs) with random networks. I found an overrepresentation of positive predictions (i.e. the species are predicted to increase their abundance) and an underrepresentation of negative predictions for the top species when basal species are perturbed. This occurs in both real and random systems. Considering the latter the same trend (i.e. overrepresentation of positives signs and underrepresentation of negative ones) was found when predicting the responses of basal species following perturbations on top species. I showed that these findings are due to the topological structure of the food webs (e.g. number and length of trophic paths) rather than depending on the patterning of interactions strengths. Thus, the responses of top species following perturbations on basal species are predictable, while the same trend does not hold when studying the responses of basal species after perturbations targeted on top species. These results are particularly relevant and interesting considering the importance of basal and top species as target for many anthropogenic impacts.
This thesis contributes to unfold a path toward: 1) the understanding of the effect of disturbance on ecological communities and ecosystems; 2) an improved comprehension of the interplay between top-down and bottom-up control; 3) the capability to deal with uncertainty in assessing the response of communities and ecosystems in the face of disturbance. I used relatively simple methodologies that focus on the qualitative arrangement of trophic interactions. This may seem a limitation. However, I show there are cases for which even the study of qualitative data can be of crucial importance in terms of management (i.e. ecosystem-based management).I cambiamenti ambientali in atto richiedono un miglioramento delle conoscenze su struttura e funzionamento dei sistemi naturali attraverso un approccio olistico. Una visione d’insieme potrebbe aiutare a comprendere meglio la risposta degli ecosistemi alle perturbazioni. E’ stato provato che lo studio dei network ecologici è utile per comprendere la struttura e le dinamiche degli ecosistemi. In questa tesi presento due tecniche modellistiche: l’analisi topologica di food web (capitolo 2) e la loop analysis (capitolo 3 e 4). Entrambi gli studi privilegiano l’analisi qualitativa a quella quantitativa per superare la mancanza di dati. Nel capitolo 2 ho considerato alcune caratteristiche topologiche per lo studio del funzionamento dell’ecosistema di Baja California Sur. Ho identificato, attraverso gli indici di centralità, le specie chiave e analizzato la resilienza del sistema alla rimozione delle specie definite più vulnerabili (es. precedente classificazione di alto, medio e basso rischio). Gli effetti sono stati valutati attraverso indici globali. I risultati evidenziano la resilienza strutturale della food web alle rimozioni, ma anche che la rimozione delle specie più vulnerabili cambia significatamente alcuni attributi del sistema rispetto alle rimozioni random. Nel capitolo 3 ho valutato l’evoluzione dell’ecosistema del Mar Nero nel periodo 1960-1990 attraverso la loop analysis. I modelli qualitativi indagati ricostruiscono la struttura dei legami dell’intera comunità. Ho validato i risultati emersi con indagini statistiche sulle serie temporali di biomasse per capire come la struttura delle interazioni può spiegare le variazioni nei livelli di biomassa delle variabili e quali ipotesi possono essere fatte sui drivers e i meccanismi responsabili dei cambiamenti. Nel capitolo 4 ho costruito un database di food web reali e random, che ho studiato attraverso la loop analysis, per capire come un input positivo sulle specie basali e apicali si ripercuote rispettivamente sulle specie apicali e basali. Lo scopo era quello di identificare possibili differenze nella propagazione degli effetti indiretti in risposta a input positivi che si verificano agli estremi delle food web. Ho confrontato sistemi reali (marini, terrestri e di acqua dolce) con networks random. Ho trovato una sovrarappresentazione di predizioni positive (aumento dell’abbondanza delle specie) e una sottorappresentazione di predizione negative per le specie apicali a seguito di un input positivo sulle specie basali, sia nei sistemi reali che in quelli random. Considerando questi ultimi lo stesso trend (sovrarappresentazione di segni positivi e sottorappresentazione di segni negativi) è stato trovato nelle predizioni riguardanti la risposta delle specie basali a seguito di un input sulle specie apicali. Ho mostrato che questi risultati sono dovuti alla struttura topologica delle food web (es. il numero e la lunghezza dei percorsi trofici) piuttosto che alla forza delle interazioni. Sembra che le risposte delle specie apicali a seguito di perturbazioni delle specie basali siano prevedibili, al contrario delle risposte delle specie basali a seguito di un input sulle apicali. Questi risultati sono particolarmente rilevanti e interessanti considerando l’importanza delle specie basali e apicali come target degli impatti antropici. Questa tesi contribuisce allo sviluppo di un percorso verso: 1)la comprensione degli effetti di disturbo sulle comunità ecologiche e sugli ecosistemi; 2)una migliore comprensione delle interazioni di controllo top-down e bottom-up; 3)la capacità di affrontare l'incertezza per valutare la risposta delle comunità e degli ecosistemi di fronte al disturbo. Nonostante l’uso di metodologie relativamente semplici che si concentrano sulla disposizione qualitativa delle interazioni trofiche, ho dimostrato che vi sono casi in cui anche lo studio di dati qualitativi può essere di cruciale importanza in termini di gestione.
6
Muller, Isabelle. « Restauration de marais temporaires et de pelouses méso-xériques à partir d’anciennes rizières : Rôle respectif des filtres dans l'assemblage des communautés ». Thesis, Avignon, 2013. http://www.theses.fr/2013AVIG0329/document.
Texte intégralRésumé :
La restauration écologique est considérée comme un des moyens susceptibles d’enrayer la perte de la biodiversité. Les changements d’occupation du sol peuvent être des opportunités pour restaurer des écosystèmes dégradés par les activités agricoles. C’est notamment le cas du projet participatif du domaine du Cassaïre, situé dans le delta du Rhône, qui vise à recréer sur d’anciennes rizières des écosystèmes méditerranéens favorables à l’activité cynégétique. Deux écosystèmes sont plus particulièrement visés, les marais temporaires et les pelouses méso-xériques. Les objectifs de la thèse sont de mettre en évidence les principaux mécanismes concourant à l’installation d’une communauté végétale, de tester des techniques de restauration et d'en évaluer les conséquences pour les communautés végétales mais aussi pour d'autres compartiments de l'écosystème. En l’absence d’espèces cibles dans le pool régional d’espèces, l’introduction de ces espèces est nécessaire en addition de la restauration des conditions abiotiques. L’étrépage et le transfert de sol pour la communauté des marais permettent une augmentation des espèces cibles et de la similarité avec la communauté de référence. Cette technique apparaît moins pertinente pour la communauté d’invertébrés aquatiques. Le succès contrasté du transfert de sol souligne les risques à ne pas privilégier qu’un nombre restreint d’indicateurs de restauration, ne reflétant pas l’ensemble de l’écosystème. L’étrépage de sol suivi d’un transfert de foin semble être une combinaison pertinente pour recréer la communauté végétale de pelouses, même si les résultats obtenus, probablement en raison d’une compétition élevée, sont moins convaincants que pour les marais temporaires. Nos résultats obtenus pour la grande majorité en mésocosmes, s’ils ne concernent que les premières étapes de la restauration, mettent cependant en évidence des techniques de restauration qui paraissent pertinentes pour installer certaines composantes des deux écosystèmes de référence. Ces résultats, par leurs limites, suggèrent néanmoins de privilégier la conservation in situ des habitats naturels plutôt que de chercher à les restaurer après qu’ils aient été détruitsEcological restoration is considered as one approach to slow down the loss of biodiversity. Changes in land-uses may be an opportunity to restore ecosystems degraded by agricultural activities. This is the case of the participatory project of the Cassaïre site, located in the Rhône delta, which aims at recreating Mediterranean ecosystems favorable to hunting on former ricefields. Two ecosystems are targeted, temporary wetlands and meso-xeric grasslands. The aims of the thesis are to highlight the main drivers of plant community establishment, to test restoration techniques and to evaluate their effects on plant communities but also on other compartments of the ecosystem. In the absence of target species in the regional species pool, the introduction of these species is necessary in addition to the restoration of abiotic conditions. Topsoil removal and soil transfer for wetland communities allow an increase of target species and of similarity with the reference community. This technique appears to be less relevant for aquatic invertebrate community. The contrasted successful of soil transfer highlights the risks of favoring some indicators of restoration success, as they may not reflect the entire ecosystem. Topsoil removal and hay transfer seem to be a relevant combination to recreate grassland plant community, although the results obtained are less convincing than for temporary wetland, probably due to high competition. Our results, obtained in mesocosms, even if they relate only to the early stages of recovery, provide restoration techniques that seem relevant to establish some components of the two reference ecosystems. These results, by their limitations, however, suggest focusing on in situ conservation of natural habitats rather than trying to restore them after they were destroyed.Keywords: Biodiversity, Community ecology, Restoration
7
Barros, Ceres. « Etude de la stabilité des écosystèmes à plusieurs échelles spatiales et trophiques ». Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAV013/document.
Texte intégralRésumé :
Dans un contexte de changement global qui continue de menacer les espèces et l’intégrité des écosystèmes à travers le monde, l’étude de la stabilité des écosystèmes n’a jamais été aussi importante. Jusqu’à aujourd’hui, la plupart des études sur la stabilité des écosystèmes se sont centrées sur des écosystèmes simples et des perturbations individuelles, en focalisant généralement sur le comportement de propriétés écosystémiques particulières, comme les indices de productivité et de diversité. Cependant, les écosystèmes sont soumis simultanément à de multiples perturbations. De plus, à grande échelle spatiale, différents écosystèmes se succèdent, chacun répondant différemment à une perturbation donnée. L’étude de la stabilité des écosystèmes doit donc progresser vers des approches plus intégratives qui seront informatives à des échelles pertinentes pour la gestion des écosystèmes. Cette thèse est un pas en avant dans cette direction. Ici, j’ai utilisé plusieurs approches pour évaluer la façon dont de multiples facteurs de changement global, tels que les changements climatiques graduels et extrêmes et les changements d’usage du sol, affectent la stabilité des écosystèmes à grande échelle spatiale, du point de vue d’un seul niveau trophique à un point de vue multitrophique.Je commence par souligner l’importance de considérer les interactions entre les changements climatiques graduels et extrêmes, en conjonction avec les changements de l’usage du sol, pour la gestion de paysages hétérogènes, comme les Alpes européennes. En utilisant un modèle de végétation dynamique et spatialement explicite, je montre qu’une augmentation de la fréquence et de l’intensité de la sécheresse pourrait drastiquement changer les tendances d’embroussaillement des habitats ouverts alpins et subalpins qui sont généralement prévues par les projections ne prenant pas en compte ces évènements extrêmes dans le futur. J’ai ensuite étudié si la sécheresse et le réchauffement climatique progressif amenaient les communautés végétales à souffrir des transitions différentes, en utilisant une approche innovatrice dans laquelle les états des communautés sont décrits d’une façon multidimensionnelle. Je montre que bien que les effets de la sécheresse sur la structure des forêts et des pâturages ne devraient pas trop affecter les trajectoires à long terme causées seulement par le réchauffement climatique graduel, ils devraient rendre les communautés forestières plus instables que les prairies dans le futur. Cependant, l’analyse des réponses de la végétation reste limitée à un seul niveau trophique. Vu que les réseaux trophiques représentent les flux d’énergie dans un écosystème, l’étude de leur stabilité aux perturbations devrait fournir des informations plus précises sur la stabilité globale de l’écosystème. Donc, j’ai aussi étudié la stabilité des réseaux trophiques dans les aires protégées européennes face à des scénarios futurs d’usage du sol et de climat. Mes résultats montrent que ces réseaux trophiques peuvent être très sensibles aux changements climatiques, même s’ils ne sont soumis à aucun changement d’usage du sol. Notamment, je montre que la prise en compte des phénomènes de dispersion des espèces aura un impact important sur la robustesse des réseaux, et je souligne l’importance de leur prise en compte pour la gestion des écosystèmes.Dans ma thèse, je démontre que les concepts de stabilité de l’écosystème peuvent et doivent être appliqués à des échelles pertinentes pour la gestion des écosystèmes, tout en adoptant la nature multidimensionnelle des écosystèmesAs global change threatens ecosystems worldwide with biodiversity loss, studying ecosystem stability has never been so important. Most ecosystem stability studies have heretofore focused on single ecosystems and disturbances, usually following the behaviour of particular ecosystem properties, such as productivity and diversity indices. However, ecosystems are subjected to multiple disturbances simultaneously and at large spatial scales different ecosystems co-occur, each responding specifically to any given disturbance. Hence, the study of ecosystem stability needs to move towards approaches that can be informative at broad scales that are relevant for ecosystem management. This thesis is a step forward in this direction. Here, I used several approaches to assess how multiple global change drivers, such as climate change, extreme whether events, and land-use changes, affect ecosystem stability at landscape and larger spatial scales, and from single to multi-trophic level perspectives.I begin by highlighting the importance of considering the interactions between gradual and extreme climate changes, in conjunction with land-use changes, for the management of highly diverse landscapes, such as the European Alps. Using a spatially explicit dynamic vegetation model, I show that increasing drought frequency and intensity will likely change the trends of treeline movement expected under future gradual climate warming scenarios. I then investigated whether drought and gradual climate warming caused plant communities to shift in different ways, using n-dimensional hypervolumes to describe community states in multidimensional space. Drought effects on forest and grassland structure did not greatly change the long-term trajectories caused by gradual climate warming alone, but showed that forest communities became more unstable than grasslands in the future. However, focusing on vegetation dynamics remains limited to a single trophic level. Because trophic networks represent energy flows in an ecosystem, studying their stability to disturbances should provide more accurate information on overall ecosystem stability. Hence, I also investigated trophic network stability in European protected areas to future scenarios of land-use and climate changes. My results show that these trophic networks may be highly sensitive to climate changes, even if no land-use changes occur. Importantly, I show that considering different dispersal limitations will greatly impact network robustness, and stress the importance of accounting for these processes in ecosystem management.In my thesis, I demonstrate that ecosystem stability concepts can and should be applied at scales that are relevant for management, while embracing the multidimensional nature of ecosystems
8
Loiret, Richard. « Le Bilan écologique. Mesurer la perturbation anthropogénique de l’Ecosphère et de la Biosphère (un bilan de l'Anthropocène). Caractériser les voies du Développement écologique des territoires ». Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLV001/document.
Texte intégralRésumé :
(Résumé de la thèse) Ayant constaté l’échec de ses Objectifs 2010 pour la biodiversité, dont, entre autres, l’incapacité de l’Empreinte écologique à rendre compte de la biodiversité, la Convention sur la Diversité Biologique a adopté en 2011 "Les objectifs d’Aichi (2011-2020) pour la biodiversité". Parmi ceux-ci les objectifs 1 et 2 concernent la prise de conscience des valeurs de la biodiversité, leur intégration dans les processus de planification nationaux et locaux de développement, et leur incorporation dans les comptabilités nationales. Ce en quoi ces objectifs de la CDB convergent désormais avec ceux des Nations Unies concernant le Système de Comptabilité Economique et Environnementale (SCEE). La présente thèse s’inscrit dans ce cadre de questionnement unifié. Elle a le double objectif : (a) de rechercher, fonder et mettre au point une unité de mesure biophysique de la diversité biologique caractérisant tout aussi bien l’ordre naturel que le désordre anthropogénique, et (b) d’incorporer celle-ci dans un nouveau système de comptabilité physique, le Bilan écologique. Celui-ci est susceptible de comparer, à toutes échelles territoriales, le Passif écologique des collectivités urbaines, vu comme le reflet biophysique de leur comptabilité monétaire, à l’Actif écologique de leurs espaces naturels, afin de révéler les relations de cause à effet, et de signifier les impacts cumulés de la perturbation anthropogénique sur l’Ecosphère et la Biosphère. Il aurait ainsi vocation, à terme, à nous permettre de caractériser les voies d’un développement véritablement écologique des territoires(Abstract of the thesis) Having noted the failure of its 2010 targets for biodiversity, including, among others, the inability of the Ecological Footprint to account for biodiversity, the Convention on Biological Diversity adopted in 2011 "The 2011-2020 Aichi Targets for biodiversity". Among these, objectives 1 and 2 concern awareness of the values of biodiversity, their integration into national and local development planning process, and their incorporation into national accounts. This how these objectives of the CBD converge now with those of the United Nations for the System of Environmental-Economic Accounting (SEEA). This thesis lie within this unified questioning framework. It has the double purpose : (a) of searching for, founding and developing a biophysical measurement unit of biodiversity, characterizing just as well the natural order as the anthropogenic disorder, and (b) to incorporate it into a new physical accounting system, the Ecological balance sheet. The latter is likely to compare, for all territorial scales, the Ecological liability of urban communities, seen as the biophysical reflection of their monetary accounting, to the Ecological asset of their natural spaces, in order to reveal the relationships of cause and effect, and to signify the cumulative impacts of anthropogenic disturbance on the Ecosphere and the Biosphere. In the end, it would have so vocation to enable us to characterize the ways of a truly ecological development of the territories
9
Bush, Timothy. « Response to environmental perturbations in microbial nutrient-cycling ecosystems ». Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/15789.
Texte intégralRésumé :
The habitability of Earth is dependent upon the global recycling of elements essential for life, such as nitrogen, sulfur and carbon. Nutrient-cycling by micro-organisms is vital to these biogeochemical cycles because many key steps are mediated primarily, or exclusively, by microbial life. The dynamics of these cycles are highly complex, and environmental perturbations (such as changes in the oceanic oxygen concentration) can have unexpected or catastrophic effects; often causing abrupt switches between chemical states. Despite the importance of these environmental perturbations however, few theoretical models have addressed how they affect the dynamical behaviour of nutrient-cycling microbial ecosystems. In this work, we investigate the effect of environmental perturbations on microbially-mediated nutrient cycles and assess the likelihood of "sudden transitions" between chemical states of the ecosystem occurring in a variety of ecological contexts. To do this, we first use computational modelling of microbial nutrient-cycling, using a "box model" approach. We then move on to an experimental study using the microbial sulfur cycle as a model ecosystem, with freshwater pond sediment/water microcosms. These microcosms have the advantage of retaining many of the features of the real ecosystem (such as microbial diversity, spatial structure, and abiotic interactions) while allowing the controlled manipulation of environmental perturbations. We study these microcosms using a combination of chemical measurements and high-throughput sequencing of the microbial community. Finally, we return to the computational side, and attempt to reproduce chemical data from our experiments in a mathematical model containing realistic abiotic chemical interactions.
10
Vincent, Florian. « Fonctionnement et structure des écosystèmes aquatiques en réponse aux perturbations anthropiques de type bottom-up et top-down ». Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS472.
Texte intégralRésumé :
Les activités humaines amplifient ou interfèrent régulièrement avec les forçages « top-down » et « bottom-up » sur les écosystèmes. Pourtant, la réponse des communautés à ces perturbations reste mal comprise. Ma thèse a pour objet de mesurer les effets des top-prédateurs et des nutriments sur la structure et le fonctionnement d’écosystèmes aquatiques expérimentaux. J’ai étudié dans des mésocosmes pélagiques de 9,5 m³ l’effet d’un forçage top-down induit par deux espèces de poissons. Je montre que ces changements de top-prédateurs s’accompagnent d’une réorganisation profonde de la structure du réseau trophique planctonique. Les réorganisations dépendent en partie de la taille des organismes et de leur comportement antiprédateur, mais c’est la phylogénie qui permet le plus efficacement de prédire la réponse du zooplancton aux poissons et les effets en cascade qui en découlent. J’ai également étudié la réponse à un forçage bottom-up par ajouts de phosphore et d’azote dans des macrocosmes de 750 m³ incluant une zone littorale végétalisée. Je montre que l’ajout de nutriments a eu un effet marqué sur la biomasse des producteurs primaires (biofilm, macrophytes littoraux), que les ajouts induisent une abondance plus forte de juvéniles de perche mais la biomasse du zooplancton n’est pas modifiée. La stœchiométrie des organismes et l’activité bactérienne n’ont été que peu changées par l’enrichissement. Ces résultats suggèrent que les effets des forçages bottom-up dans les milieux pélagiques sont bien prédits par la théorie des chaînes trophique mais, à l’échelle d’écosystèmes complexes, les macrophytes et le biofilm peuvent fortement atténuer la réponse à l’enrichissementHuman activities regularly amplify or interfere with top-down and bottom-up forcing on ecosystems. However, the communities' response to these disruptions remains poorly understood. My thesis aims to measure the effects of top-predators and nutrients on the structure and functioning of experimental aquatic ecosystems. I studied in 9.5 m³ pelagic mesocosms the effect of top-down forcing induced by two fish species. I show that these changes in top-predators are accompanied by a profound reorganization of the structure of the planktonic food web. Reorganizations depend in part on the size of organisms and their anti-predatory behaviour, but phylogeny is the most effective way to predict zooplankton response to fish and the resulting cascading effects. I also studied the response to bottom-up forcing by adding phosphorus and nitrogen in 750 m³ macrocosms including a vegetated littoral area. I show that the addition of nutrients has had a significant effect on the biomass of primary producers (biofilm, littoral macrophytes), that the additions induce a higher abundance of juveniles perch but the zooplankton biomass is not modified. The stoichiometry of organisms and bacterial activity were only slightly changed by enrichment. These results suggest that the effects of bottom-up forcings in pelagic environments are well predicted by food chain theory, but at the scale of complex ecosystems, macrophytes and biofilm can strongly reduce the response to enrichment
Livres sur le sujet "Ecosystem perturbation"
1
O, Ravera, et European Ecological Symposium (5th : 1989 : Siena, Italy), dir. Terrestrial and aquatic ecosystems : Perturbation and recovery. New York : Ellis Horwood, 1991.
Trouver le texte intégral
2
Ceccaldi, Hubert-Jean, Yves Hénocque, Yasuyuki Koike, Teruhisa Komatsu, Georges Stora et Marie-Hélène Tusseau-Vuillemin, dir. Marine Productivity : Perturbations and Resilience of Socio-ecosystems. Cham : Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-13878-7.
Texte intégral
3
Richard, Carignan, Steedman Robert John 1958-, Sustainable Forest Management Network et Ontario. Centre for Northern Forest Ecosystem Research., dir. Impacts of major watershed perturbations on aquatic ecosystems. Ottawa : National Research Council of Canada, 2000.
Trouver le texte intégral
4
Lebel, Jean. Health : An ecosystem approach. Ottawa : International Development Research Centre, 2003.
Trouver le texte intégral
5
B, Spies Robert, dir. Long-term ecological change in the Northern Gulf of Alaska. Amsterdam : Elsevier, 2007.
Trouver le texte intégral
6
Leavitt, Allison R. The perturbation-resilience model : Lessons from regional ecosystem management : botany, Miami University special committee degree. 1999.
Trouver le texte intégral
7
Leavitt, Allison R. The perturbation-resilience model : Lessons from regional ecosystem management : botany, Miami University special committee degree. 1999.
Trouver le texte intégral
8
Monechi, Simonetta, Rodolfo Coccioni et Michael Rampino. Large Ecosystem Perturbations : Causes and Consequences. Geological Society of America, 2007. http://dx.doi.org/10.1130/spe424.
Texte intégral
9
Large ecosystem perturbations : Causes and consequences. Boulder, Colo : Geological Society of America, 2007.
Trouver le texte intégral
10
Monechi, Simonetta. Large Ecosystem Perturbations : Causes and Consequences. Geological Society of Amer, 2007.
Trouver le texte intégralChapitres de livres sur le sujet "Ecosystem perturbation"
1
Stahl, David A. « Phylogenetically Based Studies of Microbial Ecosystem Perturbation ». Dans ACS Symposium Series, 373–90. Washington, DC : American Chemical Society, 1988. http://dx.doi.org/10.1021/bk-1988-0379.ch029.
Texte intégral
2
Carpenter, Stephen R. « The Need for Large-Scale Experiments to Assess and Predict the Response of Ecosystems to Perturbation ». Dans Successes, Limitations, and Frontiers in Ecosystem Science, 287–312. New York, NY : Springer New York, 1998. http://dx.doi.org/10.1007/978-1-4612-1724-4_12.
Texte intégral
3
Sun, Guodong, et Mu Mu. « Responses of Terrestrial Ecosystem to Climate Change : Results from Approach of Conditional Nonlinear Optimal Perturbation of Parameters ». Dans Data Assimilation for Atmospheric, Oceanic and Hydrologic Applications (Vol. III), 527–47. Cham : Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-43415-5_24.
Texte intégral
4
Patra, Ritwik, Saubhik Mitra et Suprabhat Mukherjee. « Perturbation of the Health of the Riverine Ecosystem and its Impact on the Biogeochemical, Ecological, and Molecular Perspectives ». Dans River Health and Ecology in South Asia, 197–249. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-83553-8_10.
Texte intégral
5
Otero, Iago. « Social-Ecological Transformation to Coexist with Wildfire : Reflecting on 18 Years of Participatory Wildfire Governance ». Dans Urban Resilience to the Climate Emergency, 147–75. Cham : Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-07301-4_7.
Texte intégralRésumé :
AbstractThe risk of devastating wildfires – exacerbated by climate change – poses a threat to urban areas worldwide. There is a pressing need to strengthen societal efforts to coexist with this perturbation by creating resilient social-ecological systems. To enable this, a significant social-ecological transformation of wildfire-prone regions seems to be required. Here, I reflect on my experience in three projects of participatory wildfire governance conducted in the Barcelona Metropolitan Region (Spain) during the last 18 years. The goal is to learn from the experience and to sketch new transformative options to coexist with wildfire. After a literature review on the links between resilience to wildfire, adaptation and transformation, I analyse these projects with regard to their achievements, challenges and potential new transformative avenues. The analysis shows the crucial role that a locally rooted civil society can have when it is able to network with key agencies and actors over the long term. It also shows the importance of developing integrative wildfire planning networks where different ecosystem services and values are considered in successive phases of public deliberation between actors, citizens and wildfire managers. It is concluded that deepening the transdisciplinary content of participatory wildfire governance can increase its transformative potential.
6
Ayyam, Velmurugan, Swarnam Palanivel et Sivaperuman Chandrakasan. « Coastal Fauna and Human Perturbation ». Dans Coastal Ecosystems of the Tropics - Adaptive Management, 91–106. Singapore : Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-13-8926-9_5.
Texte intégral
7
Trenkel, Verena, Anik Brind’Amour, Sigrid Lehuta, Pascal Lorance, Stéphanie Mahévas et Marie-Joëlle Rochet. « Indicators for Ecosystem-Based Management : Methods and Applications ». Dans Marine Productivity : Perturbations and Resilience of Socio-ecosystems, 215–21. Cham : Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-13878-7_23.
Texte intégral
8
SKIRVING, WILLIAM, GAND LIU, ALAN E. STRONG, CHUNYING LIU, JOHN SAPPER et FELIPE ARZAYUS. « EXTREME EVENTS AND PERTURBATIONS OF COASTAL ECOSYSTEMS ». Dans Remote Sensing and Digital Image Processing, 11–25. Dordrecht : Springer Netherlands, 2006. http://dx.doi.org/10.1007/1-4020-3968-9_2.
Texte intégral
9
Odibat, Zaid, et Cyrille Bertelle. « Application of Homotopy Perturbation Method for Ecosystems Modelling ». Dans Understanding Complex Systems, 51–61. Berlin, Heidelberg : Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-540-88073-8_5.
Texte intégral
10
Sasano, Masahiko, Yasuharu Nakajima, Joji Yamamoto et Yasuo Furushima. « Use of Bio-fluorescent Characteristics for Ecosystem Monitoring on Hydrothermal Deposits ». Dans Marine Productivity : Perturbations and Resilience of Socio-ecosystems, 207–13. Cham : Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-13878-7_22.
Texte intégralActes de conférences sur le sujet "Ecosystem perturbation"
1
McCarthy, Francine M. G., Caitlin S. Garner, Krystyna Kornecki, Matthew S. Schuler, Paul Michael Pilkington, Andrea M. Krueger, Miriam E. Katz et al. « TEASING OUT ANTHROPOGENIC FROM NATURAL PERTURBATION ON THE LAKE GEORGE ECOSYSTEM – EVIDENCE FROM NON-POLLEN PALYNOMORPHS IN “POLLEN SLIDES” ». Dans 53rd Annual GSA Northeastern Section Meeting - 2018. Geological Society of America, 2018. http://dx.doi.org/10.1130/abs/2018ne-311158.
Texte intégral
2
Wilson, Tyler, Abheek Chatterjee et Astrid Layton. « Developing a Supply Chain Modeling Approach to Facilitate Ecology-Inspired Design for Sustainability and Resilience ». Dans ASME 2021 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/detc2021-70782.
Texte intégralRésumé :
Abstract Supply chain policies and design efforts are traditionally focused on efficiency objectives such as reducing operational costs. With the occurrence of the most devastating pandemic in decades and the continually increasing prevalence of natural disasters, this focus has been challenged, and the need to focus on supply chain resilience has become apparent. Achieving long-lasting sustainable development in supply chains requires a balance of efficiency-focused measures that enhance economic and environmental sustainability and resiliency measures. Ecological Network Analysis has revealed a unique balance between pathway efficiency and redundancy in ecosystems’ network architecture. This enables both efficient operations under normal circumstances and resilience to perturbations. This same analysis can be used to evaluate the balance of sustainability and resilience in supply chain networks, providing insights into what kind of supply chain design and policy decisions lead to more ecosystem-like architectures. This study lays the groundwork for such efforts by studying four supply chain topologies (formed by prevalent supply chain strategies) using ENA. Inventory (storage) is not well understood in the typical flow analysis used in ENA but is an essential facet of supply chain design and must be included in a supply chain analysis. This study overcomes this limitation by proposing a method to include inventory in the ENA framework. The analysis conducted revealed two significant insights: (a) the agile supply chain strategy is the most ecologically similar and (b) it is possible that there are optimal inventory levels (given partnership strategies) to utilize bio-inspiration in supply chain design.
3
Chatterjee, Abheek, Richard Malak et Astrid Layton. « Exploring System of Systems Resilience vs. Affordability Trade-Space Using a Bio-Inspired Metric ». Dans ASME 2020 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/detc2020-22396.
Texte intégralRésumé :
Abstract The objective of this study is to investigate the value of an ecologically inspired architectural metric called the Degree of System Order in the System of Systems (SoS) architecting process. Two highly desirable SoS attributes are the ability to withstand and recover from disruptions (resilience) and affordability. In practice, more resilient SoS architectures are less affordable and it is essential to balance the trade-offs between the two attributes. Ecological research analyzing long-surviving ecosystems (nature’s resilient SoS) using the Degree of System Order metric has found a unique balance of efficient and redundant interactions in their architecture. This balance implies that highly efficient ecosystems tend to be inflexible and vulnerable to perturbations while highly redundant ecosystems fail to utilize resources effectively for survival. Motivated by this unique architectural property of ecosystems, this study investigates the response to disruptions vs. affordability trade-space of a large number of feasible SoS architectures. Results indicate that the most favorable SoS architectures in this trade-space share a specific range of values of Degree of System Order. This suggests that Degree of System Order can be a key metric in engineered SoS development. Evaluating the Degree of System Order does not require detailed simulations and can, therefore, guide the early stage SoS design process towards more optimal SoS architectures.
4
Uzelac, Branka, Dragana Stojičić, Snežana Budimir, Svetlana Tošić, Bojan Zlatković, Saša Blagojević, Branislav Manić, Mirjana Janjanin et Violeta Slavkovska. « ESSENTIAL OILS AS POTENTIAL BIOCONTROL PRODUCTS AGAINST PLANT PATHOGENS AND WEEDS : IN VITRO CULTURE APPROACH ». Dans XXVII savetovanje o biotehnologiji. University of Kragujevac, Faculty of Agronomy, 2022. http://dx.doi.org/10.46793/sbt27.345u.
Texte intégralRésumé :
Secondary metabolism in plant plays a major role in the survival of the plant in its ecosystem, mediating the interaction of the plant with its environment. Plant bioactive compounds are biosynthesized as a defensive strategy of plants in response to natural perturbations. A number of biological effects have been associated with the main monoterpenoids detected in investigated Micromeria spp. and Clinopodium spp. essential oils. One alternative for the production of these prospective biocontrol products is in vitro plant tissue culture. Our data suggest that the metabolic potential of in vitro shoot cultures of selected species can be manipulated by varying in vitro culture conditions.
5
Ishimatsu, Atsushi, Masahiro Hayashi, Takashi Kikkawa et Jun Kita. « Effects of CO2 Ocean Sequestration on Marine Fish ». Dans 25th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/omae2006-92198.
Texte intégralRésumé :
Ocean sequestration of CO2 has been proposed as a possible measure to retard the increasing rate of the atmospheric CO2 concentration. Since some negative impacts on marine animals and ecosystems are likely to ensue, we must carefully investigate biological effects of ocean CO2 sequestration before embarking on this mitigation practice. Considering the expected depths for CO2 ocean sequestration (> 1,000 m), it is desirable to use deep-sea animals for the experimental assessment of CO2 ocean sequestration. In addition, experimental protocols preferably mimic environmental conditions at the releasing site: CO2 concentrations vary due to mixing with surrounding seawater at low temperatures (0–2 °C) and under high pressures. This paper describes our recent experiments to elucidate the effects of high CO2 on marine fishes. A deep-sea fish Careproctus trachysoma (habitat depth 400–800 m) can be captured alive and be used for in vivo CO2 exposure experiments. 100% mortality occurred when the fish was exposed to seawater equilibrated with a gas mixture containing 3% CO2 conditions at 2 °C within 48 h, whereas mortality was never observed when shallow-water fishes (Mustelus manazo, Paralichthys olivaceus and Seriola quinqueradiata) were tested under the same CO2 conditions but at higher temperatures (17–20 °C). It is currently not clear whether this difference in mortality is due to often presumed high susceptibility of deep-sea organisms to environmental perturbations. Subsequent experiments demonstrated that low water temperature accelerates mortality by CO2 exposure. Thus, half lethal time decreased from 105h to only 5 h when water temperature was decreased from 26 °C to 20 °C (CO2 8.5%, Sillago parvisquamis). Therefore, the high CO2 susceptibility of C. trachysoma could be solely due to low water temperature. Temporally varying CO2 conditions resulted in markedly different mortality patterns when compare with mortality recorded under constant CO2 conditions. Step-wise increases in ambient CO2 resulted in much lower mortalities than under one-step increases to the same CO2 levels. Further, a sudden drop of CO2 from 9–10% CO2 to air level (0.038%) killed all the surviving fish within a few minutes.
Rapports d'organisations sur le sujet "Ecosystem perturbation"
1
Tronstad, Lusha. Aquatic invertebrate monitoring at Agate Fossil Beds National Monument : 2019 data report. National Park Service, avril 2022. http://dx.doi.org/10.36967/nrds-2293128.
Texte intégralRésumé :
Monitoring ecosystems is vital to understanding trends over time and key to detecting change so that managers can address perturbations. Freshwater streams are the lifeblood of the surrounding landscape, and their health is a measure of the overall watershed integrity. Streams are the culmination of upland processes and inputs. Degradation on the landscape as well as changes to the stream itself can be detected using biota living in these ecosystems. Aquatic invertebrates are excellent indicators of ecosystem quality because they are relatively long-lived, sessile, diverse, abundant and their tolerance to perturbation differs. Aquatic invertebrates were monitored at three sites along the Niobrara River at Agate Fossil Beds National Monument in 2019 completing 23 years of data using Hester-Dendy and Hess samplers. Hess samplers are artificial multi-plate samplers suspended in the water column to allow invertebrates to colonize and Hess samples collect invertebrates in a known area on natural substrate and vegetation. We identified 45 invertebrate taxa from four phyla (Annelida, Arthropoda, Mollusca, Nematoda) using both samplers in the Niobrara River (Appendix A and B). Hester-Dendy samplers collected 4 taxa not found in Hess samples and Hess samples collected 17 taxa not collected with Hester-Dendy samplers. Hess samples captured more (91%) than Hester-Dendy samples (62%). Crustacea, Diptera and Ephemeroptera were the most abundant groups of invertebrates collected in the Niobrara River. The proportion of Insecta, Annelida, Trichoptera and Diptera differed between Hester-Dendy and Hess samples (p < 0.05). EPT richness, proportion EPT taxa and Hilsenhoff’s Biotic Index (HBI) (p < 0.0001) differed between sampler types, but taxa richness, taxa diversity and evenness (p > 0.29) did not. We collected the highest density of invertebrates at the Agate Middle site. Agate Spring Ranch had the lowest taxa richness and HBI, and the highest proportion of EPT taxa. HBI at the sites ranged from 4.0 to 6.3 (very good to fair from Hilsenhoff 1987) using the Hester-Dendy and 5.2 to 6.9 (good to fairly poor from Hilsenhoff 1987) using the Hess sampler.
2
Taucher, Jan, et Markus Schartau. Report on parameterizing seasonal response patterns in primary- and net community production to ocean alkalinization. OceanNETs, novembre 2021. http://dx.doi.org/10.3289/oceannets_d5.2.
Texte intégralRésumé :
We applied a 1-D plankton ecosystem-biogeochemical model to assess the impacts of ocean alkalinity enhancement (OAE) on seasonal changes in biogeochemistry and plankton dynamics. Depending on deployment scenarios, OAE should theoretically have variable effects on pH and seawater pCO2, which might in turn affect (a) plankton growth conditions and (b) the efficiency of carbon dioxide removal (CDR) via OAE. Thus, a major focus of our work is how different magnitudes and temporal frequencies of OAE might affect seasonal response patterns of net primary productivity (NPP), ecosystem functioning and biogeochemical cycling. With our study we aimed at identifying a parameterization of how magnitude and frequency of OAE affect net growth rates, so that these effects could be employed for Earth System Modell applications. So far we learned that a meaningful response parameterization has to resolve positive and negative anomalies that covary with temporal shifts. As to the intricacy of the response patterns, the derivation of such parameterization is work in progress. However, our study readily provides valuable insights to how OAE can alter plankton dynamics and biogeochemistry. Our modelling study first focuses at a local site where time series data are available (European Station for Time series in the Ocean Canary Islands ESTOC), including measurements of pH, concentrations of total alkalinity, dissolved inorganic carbon (DIC), chlorophyll-a and dissolved inorganic nitrogen (DIN). These observational data were made available by Andres Cianca (personal communication, PLOCAN, Spain), Melchor Gonzalez and Magdalena Santana Casiano (personal communication, Universidad de Las Palmas de Gran Canaria). The choice of this location was underpinned by the fact that the first OAE mesocosm experiment was conducted on the Canary Island Gran Canaria, which will facilitate synthesizing our modelling approach with experimental findings. For our simulations at the ESTOC site in the Subtropical North Atlantic we found distinct, non-linear responses of NPP to different temporal modes of alkalinity deployment. In particular, phytoplankton bloom patterns displayed pronounced temporal phase shifts and changes in their amplitude. Notably, our simulations suggest that OAE can have a slightly stimulating effect on NPP, which is however variable, depending on the magnitude of OAE and the temporal mode of alkalinity addition. Furthermore, we find that increasing alkalinity perturbations can lead to a shift in phytoplankton community composition (towards coccolithophores), which even persists after OAE has stopped. In terms of CDR, we found that a decrease in efficiency with increasing magnitude of alkalinity addition, as well as substantial differences related to the timing of addition. Altogether, our results suggest that annual OAE during the right season (i.e. physical and biological conditions), could be a reasonable compromise in terms of logistical feasibility, efficiency of CDR and side-effects on marine biota. With respect to transferability to global models, the complex, non-linear responses of biological processes to OAE identified in our simulations do not allow for simple parameterizations that can easily adapted. Dedicated future work is required to transfer the observed responses at small spatiotemporal scales to the coarser resolution of global models.