Articles de revues : « Ecosystem perturbation »

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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, n^o 1838 (14 septembre 2016) : 20161496. http://dx.doi.org/10.1098/rspb.2016.1496.

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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.

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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, n^o 6 (29 novembre 2011) : 883–93. http://dx.doi.org/10.5194/npg-18-883-2011.

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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.

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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.

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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.

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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, n^o 9 (13 septembre 2021) : 1208. http://dx.doi.org/10.3390/e23091208.

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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.

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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.

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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.

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Healey, Katherine, Adam H. Monahan et Debby Ianson. « Perturbation dynamics of a planktonic ecosystem ». Journal of Marine Research 67, n^o 5 (1 septembre 2009) : 637–66. http://dx.doi.org/10.1357/002224009791218841.

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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.

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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.

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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, n^o 2181 (31 août 2020) : 20190355. http://dx.doi.org/10.1098/rsta.2019.0355.

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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’.

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Straškraba, M. « Terrestrial and aquatic ecosystem. Perturbation and recovery ». Ecological Modelling 64, n^o 1 (octobre 1992) : 77–79. http://dx.doi.org/10.1016/0304-3800(92)90052-g.

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Mu, M., et B. Wang. « Nonlinear instability and sensitivity of a theoretical grassland ecosystem to finite-amplitude perturbations ». Nonlinear Processes in Geophysics 14, n^o 4 (19 juillet 2007) : 409–23. http://dx.doi.org/10.5194/npg-14-409-2007.

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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.

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Kay, M. K. « Linking biosecurity and biogeography ». New Zealand Plant Protection 62 (1 août 2009) : 103–8. http://dx.doi.org/10.30843/nzpp.2009.62.4778.

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The unfathomable complexity of species interactions within biological systems tempts us to impose tidy concepts in an effort to predict or explain how ecosystems react to perturbation through species extinction or invasion The Equilibrium Theory of Island Biogeography (ETIB) contends that islands are inherently at risk of both invasion and extinction of species The appealing logic of the ETIB and a general consensus that biodiversity is linked to ecosystem resilience ie that the loss of biodiversity will result in a loss of ecosystem stability have been cemented into mainstream ecology However the biodiversity ecosystem resilience debate is far from resolved The ETIB treats species as empirical entities and takes no account of how species interactions evolve to determine the way ecosystems function The Island Resource Allocation (IRA) hypothesis offers a testable alternative explanation of how ecosystems function and could be considered by biosecurity agencies in assessing ecological risk of introduced species

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Chávez, V. Alonso, et K. Michaelian. « Predicting Ecosystem Response to Perturbation from Thermodynamic Criteria ». Journal of Modern Physics 02, n^o 06 (2011) : 627–35. http://dx.doi.org/10.4236/jmp.2011.226073.

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Link, Jason S., Fabio Pranovi, Simone Libralato, Marta Coll, Villy Christensen, Cosimo Solidoro et Elizabeth A. Fulton. « Emergent Properties Delineate Marine Ecosystem Perturbation and Recovery ». Trends in Ecology & ; Evolution 30, n^o 11 (novembre 2015) : 649–61. http://dx.doi.org/10.1016/j.tree.2015.08.011.

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Tainaka, Kei-ichi, et Tomoyuki Sakata. « Perturbation Experiment and Parity Law in a Cyclic Ecosystem ». Journal of the Physical Society of Japan 68, n^o 3 (15 mars 1999) : 1055–56. http://dx.doi.org/10.1143/jpsj.68.1055.

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Chmolowska, Dominika. « Higher Vulnerability of Heterotrophic Soil Respiration to Temperature Drop in Fallows than in Meadows ». Journal of Climate Change 7, n^o 1 (3 février 2021) : 57–67. http://dx.doi.org/10.3233/jcc210005.

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The present study examines the difference between stability and climatic factors of soil microbial communities in two ecosystem types with similar plant biomass, while differing in plant diversity, successional stage and complexity. Observations of variation in stability can be applied to climate change investigations, a topic of current pivotal importance. We compared responses of soil basal respiration to short time perturbation in soils collected from six established (meadow) and six early successional (fallow) ecosystems by exposing them to thermal and water stress. Resistance and resilience indices were calculated to describe how much a system was affected by and recovered from perturbation. The soil’s physico-chemical properties and plant community composition were identified and used for correlation and regression analyses with the stability indices. There was a smaller relative change in soil respiration in meadows than in fallows as temperature decreased from 22 to 10°C. Resistance to coolness was correlated to higher soil pH, while resilience to plant species richness. The drying-rewetting experiment highlighted that the stability indices became non-linear when a data set had high variations. Soil microbial communities in a more complex and mature ecosystem type (meadow) were more stable under a moderate perturbation. This might have been supported by co-occurring factors, with soil pH being the most influential. The slightly acidic fallow soil might have a higher potential for carbon sequestration than neutral meadow soil.

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Sprules, W. Gary, et M. Munawar. « Plankton Size Spectra in Relation to Ecosystem Productivity, Size, and Perturbation ». Canadian Journal of Fisheries and Aquatic Sciences 43, n^o 9 (1 septembre 1986) : 1789–94. http://dx.doi.org/10.1139/f86-222.

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Quantification and comparisons of the structure of open-water plankton communities from 25 inland lakes of Ontario, from the Laurentian Great Lakes Superior, Huron, St. Clair, Ontario, and Erie, and from the Central Gyre in the North Pacific Ocean were made on the basis of the normalized biomass size spectrum. Residual variation around the fitted straight lines (corresponding to a theoretical steady state) was least for the large, oligotrophic Lake Superior and the North Pacific Gyre and greatest for eutrophic Saginaw Bay and shallow Lake Erie, suggesting progressive departure from steady-state conditions with increasing system productivity. The slopes of the normalized spectra decrease with increasing eutrophy, indicating that nannoplankton abundances are similar in all communities studied, but that associated zooplankton abundances vary by 2.5 orders of magnitude. Our results suggest that parameterization of particle-size models for prediction of potential fish production must be adjusted according to the size and productivity of the ecosystem, and that routine monitoring of communities by the normalized biomass spectrum could provide early warning of nutrient or toxic stress in aquatic ecosystems.

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Blanchfield, Paul J., Michael J. Paterson, John A. Shearer et David W. Schindler. « Johnson and Vallentyne’s legacy : 40 years of aquatic research at the Experimental Lakes Area ». Canadian Journal of Fisheries and Aquatic Sciences 66, n^o 11 (novembre 2009) : 1831–36. http://dx.doi.org/10.1139/f09-148.

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Wally Johnson and Jack Vallentyne played key roles in the establishment of the Experimental Lakes Area (ELA), which comprises a research team, a set of protected lakes, and a field station, with the mandate to quantify anthropogenic impacts to lakes through whole-ecosystem manipulation and monitoring. We begin this collection of papers, celebrating four decades of aquatic research at the ELA, by reflecting on the historical relevance and scientific milestones of the ELA. The remaining papers encompass themes at the core of ELA research: long-term ecological monitoring of unimpacted reference lakes, ecosystem responses to anthropogenic stressors through whole-system experimentation, recovery of manipulated ecosystems from perturbation, and detailed mechanistic studies. Utilizing these approaches, papers in this issue examine a wide variety of anthropogenic impacts on freshwater including the ecosystem effects of climate change, recovery from lake acidification, upland and wetland flooding on methyl mercury levels in biota, endocrine-disrupting chemicals on fish populations, and freshwater aquaculture. These studies emphasize the value of long-term monitoring and experimentation at the ecosystem scale for understanding human impacts on freshwaters.

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Kumar Singh, Piush, et T. Som. « Fractional Ecosystem Model and Its Solution by Homotopy Perturbation Method ». International Journal of Ecosystem 2, n^o 5 (1 décembre 2012) : 140–49. http://dx.doi.org/10.5923/j.ije.20120205.06.

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Rao, D. Subba, et M. Subba Rao. « A man‐induced ecosystem perturbation in the river Kshipra, India ». International Journal of Environmental Studies 30, n^o 2-3 (décembre 1987) : 137–43. http://dx.doi.org/10.1080/00207238708710388.

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Tainaka, Kei-ichi. « Perturbation expansion and optimized death rate in a lattice ecosystem ». Ecological Modelling 163, n^o 1-2 (mai 2003) : 73–85. http://dx.doi.org/10.1016/s0304-3800(02)00414-3.

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Quine, Timothy, Dali Guo, Sophie M. Green, Chenglong Tu, Iain Hartley, Xinyu Zhang, Jennifer Dungait et al. « Ecosystem service delivery in Karst landscapes : anthropogenic perturbation and recovery ». Acta Geochimica 36, n^o 3 (9 juin 2017) : 416–20. http://dx.doi.org/10.1007/s11631-017-0180-4.

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Rahim, Akif, Xander Wang, Neelam Javed, Farhan Aziz, Amina Jahangir et Tahira Khurshid. « The Perturbation of Mangla Watershed Ecosystem in Pakistan Due to Hydrological Alteration ». Water 15, n^o 4 (8 février 2023) : 656. http://dx.doi.org/10.3390/w15040656.

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Hydrological regimes influence an aquatic ecosystem’s biotic composition, structure, and functioning. But construction of dams or anthropogenic activities substantially alter the hydrologic regimes. In this study, we used a method named as the “Indicators of Hydrologic Alteration” to examine the degree of hydrologic alteration at seven flow gauge stations in the Mangla watershed. The assessment of alteration is carried out according to the Range of Variability (RVA). This method relies on analyzing hydrologic data obtained from existing measurement points (e.g., stream gauges) within an ecosystem or model-generated data. We used 33 parameters categorized into 5 groups based on magnitude, duration, frequency, timing, and rate of change to characterize hydrologic variation within a year statistically. We then examine the hydrologic perturbations by comparing the measure of central tendency and dispersion for each parameter between the “pre-impact (1967–1994)” and “post-impact (1995–2014)” periods. The results show that within the Mangla watershed, the high alteration was noted in the magnitude of monthly flows and extreme flows at Azad Pattan, Gari Habibullah, Palote and at Muzafarabad stations. The flow at Domel and Kohala stations are found in low hydrological alteration among all groups of indicators. The study indicates that Neelum Basin at Muzaffarabad has significantly high alteration with maximum negative values. On the other hand, a high frequency of alteration observed in the monthly flows and extreme water conditions. Overall, a moderate alteration is observed in the whole watershed, which may produce adverse effects on the aquatic ecosystem of the Mangla watershed.

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Bouskill, N. J., W. J. Riley et J. Tang. « Meta-analysis of high-latitude nitrogen-addition and warming studies imply ecological mechanisms overlooked by land models ». Biogeosciences Discussions 11, n^o 8 (18 août 2014) : 12375–414. http://dx.doi.org/10.5194/bgd-11-12375-2014.

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Abstract. Accurate representation of ecosystem processes in land models is crucial for reducing predictive uncertainty in energy and greenhouse gas feedbacks with the atmosphere. Here we describe an observational and modeling meta-analysis approach to benchmark land models, and apply the method to the land model CLM4.5 with two versions of belowground biogeochemistry. We focused our analysis on the above and belowground high-latitude ecosystem responses to warming and nitrogen addition, and identified mechanisms absent, or poorly parameterized in CLM4.5. While the two model versions predicted similar trajectories for soil carbon stocks following both types of perturbation, other variables (e.g., belowground respiration) differed from the observations in both magnitude and direction, indicating the underlying mechanisms are inadequate for representing high-latitude ecosystems. The observational synthesis attribute these differences to missing representations of microbial dynamics, characterization of above and belowground functional processes, and nutrient competition. We use the observational meta-analyses to discuss potential approaches to improving the current models (e.g., the inclusion of dynamic vegetation or different microbial functional guilds), however, we also raise a cautionary note on the selection of data sets and experiments to be included in a meta-analysis. For example, the concentrations of nitrogen applied in the synthesized field experiments (average =72 kg ha−1 yr−1) are many times higher than projected soil nitrogen concentrations (from nitrogen deposition and release during mineralization), which preclude a rigorous evaluation of the model responses to nitrogen perturbation. Overall, we demonstrate here that elucidating ecological mechanisms via meta-analysis can identify deficiencies in both ecosystem models and empirical experiments.

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Liu, Wen, et Jianfeng Feng. « Analysis of Asymptotic and Transient Behaviors of Stochastic Ratio-Dependent Predator–Prey Model ». Mathematics 9, n^o 21 (2 novembre 2021) : 2776. http://dx.doi.org/10.3390/math9212776.

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In this paper, we focus on the asymptotic and transient dynamics of the studied ecosystem and measure the response to perturbation of the stochastic ratio-dependent predator–prey model. The method we use is mainly based on the Kronecker product and numerical simulation. Firstly, the mean-square stability matrix can be calculated from the Kronecker product, so as to compute three indicators (root-mean-square resilience, root-mean-square reactivity and root-mean-square amplification envelope) of the response to perturbation for the studied ecosystem. Since the above-measured amounts cannot be obtained explicitly, we use numerical simulation to draw the changing figures within the appropriate parameter range. Then we obtain some conclusions by comparing the numerical results. When perturbing any populations, increasing the disturbance intensity will reduce the mean-square stable area of the system. Ecologists can manage the ecosystem, reduce losses and maximize benefits according to the numerical results of the root-mean-square amplification envelope.

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Farage, Miranda A., Kenneth W. Miller et Jack D. Sobel. « Dynamics of the Vaginal Ecosystem—Hormonal Influences ». Infectious Diseases : Research and Treatment 3 (janvier 2010) : IDRT.S3903. http://dx.doi.org/10.4137/idrt.s3903.

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The vagina is a dynamic and finely tuned ecosystem in which homeostasis depends on mutually beneficial interactions between a human female and her resident microorganisms, an ecosystem that can be thrown off balance by a wide variety of both intrinsic and extrinsic factors. Although a functional equilibrium provides stability to the ecosystem considered crucial to maintaining vaginal health, “normal flora” is a concept currently being redefined. New methodologies enable molecular analyses of the vaginal microbiota which have widened the definition of “normal” from a single specific microbiological profile to a range of functional microbial equilibria dependent upon pertinent host and microbial factors. One of the strongest influences on the vaginal microbiota is the hormonal changes that define the reproductive phases of a woman's life. The vaginal environment is particularly responsive to estrogen, a hormone that creates distinctive changes in the vaginal microbiota. This review summarizes the components of a healthy vaginal ecosystem during the reproductive years, including the characteristics of a healthy equilibrium and factors that can disturb a functional balance. It also summarizes what is known about the vaginal microbiota in childhood and after menopause. Healthful ecosystems at any stage of a female's reproductive life will be characterized by a microbiota that both maintains physiological function and though changeable, adapts to normal perturbation without succumbing to disease.

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Khalighi, Moein, Guilhem Sommeria-Klein, Didier Gonze, Karoline Faust et Leo Lahti. « Quantifying the impact of ecological memory on the dynamics of interacting communities ». PLOS Computational Biology 18, n^o 6 (3 juin 2022) : e1009396. http://dx.doi.org/10.1371/journal.pcbi.1009396.

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Ecological memory refers to the influence of past events on the response of an ecosystem to exogenous or endogenous changes. Memory has been widely recognized as a key contributor to the dynamics of ecosystems and other complex systems, yet quantitative community models often ignore memory and its implications. Recent modeling studies have shown how interactions between community members can lead to the emergence of resilience and multistability under environmental perturbations. We demonstrate how memory can be introduced in such models using the framework of fractional calculus. We study how the outcomes of a well-characterized interaction model are affected by gradual increases in ecological memory under varying initial conditions, perturbations, and stochasticity. Our results highlight the implications of memory on several key aspects of community dynamics. In general, memory introduces inertia into the dynamics. This favors species coexistence under perturbation, enhances system resistance to state shifts, mitigates hysteresis, and can affect system resilience both ways depending on the time scale considered. Memory also promotes long transient dynamics, such as long-standing oscillations and delayed regime shifts, and contributes to the emergence and persistence of alternative stable states. Our study highlights the fundamental role of memory on ecological communities, and provides quantitative tools to introduce it in ecological models and analyse its impact under varying conditions.

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Sabbar, Yassine, Asad Khan et Anwarud Din. « Probabilistic Analysis of a Marine Ecological System with Intense Variability ». Mathematics 10, n^o 13 (28 juin 2022) : 2262. http://dx.doi.org/10.3390/math10132262.

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This work seeks to simulate and examine the complex character of marine predation. By taking into account the interaction between phytoplankton and zooplankton, we present a sophisticated mathematical system with a general functional response describing the ecological competition. This system is disturbed by a novel category of perturbations in the hybrid form which simulates certain unstable climatic and environmental variations. We merge between the higher-order white noise and quadratic jumps to offer an excellent overview of the complexity induced in the ecosystem. Analytically, we offer a surrogate framework to get the sharp sill between stationarity and zooplankton eradication. Our analysis enriches and improves many works by proposing an unfamiliar form of perturbation and unifying the criteria of said asymptotic characteristics. Numerically, we probe the rigor of our sill in a non-standard case: cubic white noise and quadratic leaps. We demonstrate that the increased order of perturbation has a significant effect on the zooplankton living time. This result shows that the sources of intricate fluctuations carry out an active role in the transient dynamics of marine ecological systems.

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Werba, Jo A., Alexander C. Phong, Lakhdeep Brar, Acacia Frempong-Manso, Ofure Vanessa Oware et Jurek Kolasa. « Interactions between two functionally distinct aquatic invertebrate herbivores complicate ecosystem- and population-level resilience ». PeerJ 10 (7 octobre 2022) : e14103. http://dx.doi.org/10.7717/peerj.14103.

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Resilience, the capacity for a system to bounce-back after a perturbation, is critical for conservation and restoration efforts. Different functional traits have differential effects on system-level resilience. We test this experimentally in a lab system consisting of algae consumed by zooplankton, snails, or both, using an eutrophication event as a perturbation. We examined seston settlement load, chlorophyll-a and ammonium concentration as gauges of resilience. We find that Daphnia magna increased our measures of resilience. But this effect is not consistent across ecosystem measures; in fact, D. magna increased the difference between disturbed and undisturbed treatments in seston settlement loads. We have some evidence of shifting reproductive strategy in response to perturbation in D. magna and in the presence of Physa sp. These shifts correspond with altered population levels in D. magna, suggesting feedback loops between the herbivore species. While these results suggest only an ambiguous connection between functional traits to ecosystem resilience, they point to the difficulties in establishing such a link: indirect effects of one species on reproduction of another and different scales of response among components of the system, are just two examples that may compromise the power of simple predictions.

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Richey, Jon D., Isabel P. Montañez, Yves Goddéris, Cindy V. Looy, Neil P. Griffis et William A. DiMichele. « Influence of temporally varying weatherability on CO2-climate coupling and ecosystem change in the late Paleozoic ». Climate of the Past 16, n^o 5 (22 septembre 2020) : 1759–75. http://dx.doi.org/10.5194/cp-16-1759-2020.

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Abstract. Earth's penultimate icehouse period, the late Paleozoic ice age (LPIA), was a time of dynamic glaciation and repeated ecosystem perturbation, which was under conditions of substantial variability in atmospheric pCO2 and O2. Improved constraints on the evolution of atmospheric pCO2 and O2∕CO2 ratios during the LPIA and its subsequent demise to permanent greenhouse conditions are crucial for better understanding the nature of linkages between atmospheric composition, climate, and ecosystem perturbation during this time. We present a new and age-recalibrated pCO2 reconstruction for a 40 Myr interval (∼313 to 273 Ma) of the late Paleozoic that (1) confirms a previously hypothesized strong CO2–glaciation linkage, (2) documents synchroneity between major pCO2 and O2∕CO2 changes and compositional turnovers in terrestrial and marine ecosystems, (3) lends support for a modeled progressive decrease in the CO2 threshold for initiation of continental ice sheets during the LPIA, and (4) indicates a likely role of CO2 and O2∕CO2 thresholds in floral ecologic turnovers. Modeling of the relative role of CO2 sinks and sources active during the LPIA and its demise on steady-state pCO2 using an intermediate-complexity climate–carbon cycle model (GEOCLIM) and comparison to the new multi-proxy CO2 record provides new insight into the relative influences of the uplift of the Central Pangean Mountains, intensifying aridification, and increasing mafic rock to granite rock ratio of outcropping rocks on the global efficiency of CO2 consumption and secular change in steady-state pCO2 through the late Paleozoic.

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Larina, Ekaterina, David J. Bottjer, Frank A. Corsetti, Alyson M. Thibodeau, William M. Berelson, A. Joshua West et Joyce A. Yager. « Ecosystem change and carbon cycle perturbation preceded the end-Triassic mass extinction ». Earth and Planetary Science Letters 576 (décembre 2021) : 117180. http://dx.doi.org/10.1016/j.epsl.2021.117180.

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Porcella, D. B. « Lake Acidification Mitigation Project (LAMP) : an Overview of an Ecosystem Perturbation Experiment ». Canadian Journal of Fisheries and Aquatic Sciences 46, n^o 2 (1 février 1989) : 246–48. http://dx.doi.org/10.1139/f89-034.

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Henehan, Michael J., Pincelli M. Hull, Donald E. Penman, James W. B. Rae et Daniela N. Schmidt. « Biogeochemical significance of pelagic ecosystem function : an end-Cretaceous case study ». Philosophical Transactions of the Royal Society B : Biological Sciences 371, n^o 1694 (19 mai 2016) : 20150510. http://dx.doi.org/10.1098/rstb.2015.0510.

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Pelagic ecosystem function is integral to global biogeochemical cycling, and plays a major role in modulating atmospheric CO 2 concentrations ( p CO 2 ). Uncertainty as to the effects of human activities on marine ecosystem function hinders projection of future atmospheric p CO 2 . To this end, events in the geological past can provide informative case studies in the response of ecosystem function to environmental and ecological changes. Around the Cretaceous–Palaeogene (K–Pg) boundary, two such events occurred: Deccan large igneous province (LIP) eruptions and massive bolide impact at the Yucatan Peninsula. Both perturbed the environment, but only the impact coincided with marine mass extinction. As such, we use these events to directly contrast the response of marine biogeochemical cycling to environmental perturbation with and without changes in global species richness. We measure this biogeochemical response using records of deep-sea carbonate preservation. We find that Late Cretaceous Deccan volcanism prompted transient deep-sea carbonate dissolution of a larger magnitude and timescale than predicted by geochemical models. Even so, the effect of volcanism on carbonate preservation was slight compared with bolide impact. Empirical records and geochemical models support a pronounced increase in carbonate saturation state for more than 500 000 years following the mass extinction of pelagic carbonate producers at the K–Pg boundary. These examples highlight the importance of pelagic ecosystems in moderating climate and ocean chemistry.

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Tan, Yuan Shun, et Hong Zhang. « Dynamics of the Oscillative Solution for a Non-Linear Ecosystem with Impulsive Perturbation ». Applied Mechanics and Materials 226-228 (novembre 2012) : 474–78. http://dx.doi.org/10.4028/www.scientific.net/amm.226-228.474.

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In the present paper, we investigate an impulsive predator-prey model of integrated pest management(IPM) strategy. Other than the general Holling's functional response, an S-shaped mixed functional response is considered, simultaneously, we model this system assuming that the releasing of nature enemies and spraying of pesticides are impulsive at different fixed moment, which is more realistic comparing with at the same time. With the help of Floquet's theorem, small amplitude perturbation skills and comparison theorem involving multiple Liapunov functions, we show that under some sufficient conditions, the system exists an oscillative pest eradication periodic solution, which is local stable and globally attractive. Otherwise, the system is permanent. This result(threshold) provides us a very useful information for the control of ecosystem.

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MANNING, PAUL, ELEANOR M. SLADE, SARAH A. BEYNON et OWEN T. LEWIS. « Effect of dung beetle species richness and chemical perturbation on multiple ecosystem functions ». Ecological Entomology 42, n^o 5 (30 mai 2017) : 577–86. http://dx.doi.org/10.1111/een.12421.

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Iljazovic, Aida, Urmi Roy, Eric J. C. Gálvez, Till R. Lesker, Bei Zhao, Achim Gronow, Lena Amend et al. « Perturbation of the gut microbiome by Prevotella spp. enhances host susceptibility to mucosal inflammation ». Mucosal Immunology 14, n^o 1 (20 mai 2020) : 113–24. http://dx.doi.org/10.1038/s41385-020-0296-4.

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AbstractDiverse microbial signatures within the intestinal microbiota have been associated with intestinal and systemic inflammatory diseases, but whether these candidate microbes actively modulate host phenotypes or passively expand within the altered microbial ecosystem is frequently not known. Here we demonstrate that colonization of mice with a member of the genus Prevotella, which has been previously associated to colitis in mice, exacerbates intestinal inflammation. Our analysis revealed that Prevotella intestinalis alters composition and function of the ecosystem resulting in a reduction of short-chain fatty acids, specifically acetate, and consequently a decrease in intestinal IL-18 levels during steady state. Supplementation of IL-18 to Prevotella-colonized mice was sufficient to reduce intestinal inflammation. Hence, we conclude that intestinal Prevotella colonization results in metabolic changes in the microbiota, which reduce IL-18 production and consequently exacerbate intestinal inflammation, and potential systemic autoimmunity.

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Meyerholt, Johannes, Sönke Zaehle et Matthew J. Smith. « Variability of projected terrestrial biosphere responses to elevated levels of atmospheric CO2 ; due to uncertainty in biological nitrogen fixation ». Biogeosciences 13, n^o 5 (10 mars 2016) : 1491–518. http://dx.doi.org/10.5194/bg-13-1491-2016.

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Abstract. Including a terrestrial nitrogen (N) cycle in Earth system models has led to substantial attenuation of predicted biosphere–climate feedbacks. However, the magnitude of this attenuation remains uncertain. A particularly important but highly uncertain process is biological nitrogen fixation (BNF), which is the largest natural input of N to land ecosystems globally. In order to quantify this uncertainty and estimate likely effects on terrestrial biosphere dynamics, we applied six alternative formulations of BNF spanning the range of process formulations in current state-of-the-art biosphere models within a common framework, the O-CN model: a global map of static BNF rates, two empirical relationships between BNF and other ecosystem variables (net primary productivity and evapotranspiration), two process-oriented formulations based on plant N status, and an optimality-based approach. We examined the resulting differences in model predictions under ambient and elevated atmospheric [CO2] and found that the predicted global BNF rates and their spatial distribution for contemporary conditions were broadly comparable, ranging from 108 to 148 Tg N yr−1 (median: 128 Tg N yr−1), despite distinct regional patterns associated with the assumptions of each approach. Notwithstanding, model responses in BNF rates to elevated levels of atmospheric [CO2] (+200 ppm) ranged between −4 Tg N yr−1 (−3 %) and 56 Tg N yr−1 (+42 %) (median: 7 Tg N yr−1 (+8 %)). As a consequence, future projections of global ecosystem carbon (C) storage (+281 to +353 Pg C, or +13 to +16 %) as well as N2O emission (−1.6 to +0.5 Tg N yr−1, or −19 to +7 %) differed significantly across the different model formulations. Our results emphasize the importance of better understanding the nature and magnitude of BNF responses to change-induced perturbations, particularly through new empirical perturbation experiments and improved model representation.

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Meyerholt, J., S. Zaehle et M. J. Smith. « Variability of projected terrestrial biosphere responses to elevated levels of atmospheric CO2 ; due to uncertainty in biological nitrogen fixation ». Biogeosciences Discussions 12, n^o 23 (9 décembre 2015) : 19423–80. http://dx.doi.org/10.5194/bgd-12-19423-2015.

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Abstract. Including a terrestrial nitrogen (N) cycle in Earth system models has led to substantial attenuation of predicted biosphere-climate feedbacks. However, the magnitude of this attenuation remains uncertain. A particularly important, but highly uncertain process is biological nitrogen fixation (BNF), which is the largest natural input of N to land ecosystems globally. In order to quantify this uncertainty, and estimate likely effects on terrestrial biosphere dynamics, we applied six alternative formulations of BNF spanning the range of process formulations in current state-of-the-art biosphere models within a common framework, the O-CN model: a global map of static BNF rates, two empirical relationships between BNF and other ecosystem variables (net primary productivity (NPP) and evapotranspiration), two process-oriented formulations based on plant N status, and an optimality-based approach. We examined the resulting differences in model predictions under ambient and elevated atmospheric [CO2] and found that the predicted global BNF rates and their spatial distribution for contemporary conditions were broadly comparable, ranging from 95 to 134 Tg N yr−1 (median 119 Tg N yr−1), despite distinct regional patterns associated with the assumptions of each approach. Notwithstanding, model responses in BNF rates to elevated levels of atmospheric [CO2] (+200 ppm) ranged between −4 Tg N yr−1 (−3 %) and 56 Tg N yr−1 (+42 %) (median 7 Tg N yr−1 (+8 %)). As a consequence, future projections of global ecosystem carbon storage (+281 to +353 Pg C, or +13 to +16 %), as well as N2O emission (−1.6 to +0.5 Tg N yr−1, or −19 to +7 %) differed significantly across the different model formulations. Our results emphasize the importance of better understanding the nature and magnitude of BNF responses to change-induced perturbations, particularly through new empirical perturbation experiments and improved model representation.

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Currano, Ellen D. « Ancient Bug Bites on Ancient Plants Record Forest Ecosystem Response to Environmental Perturbations ». Paleontological Society Papers 19 (octobre 2013) : 157–74. http://dx.doi.org/10.1017/s1089332600002722.

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Leaf-compression fossils with insect feeding traces are unique in providing rich, direct evidence of two levels in a fossil food web. Plant-insect associations dominate terrestrial trophic interactions, emphasizing the need to understand their ecological and evolutionary history. This paper first discusses methods of recognizing insect herbivore damage on fossil leaves and quantifying fossil insect herbivory. By conducting an unbiased insect damage census, damage frequency (percent of leaves with insect feeding damage), percent of leaf surface area removed by insects, and damage diversity (the number of discrete damage morphotypes, or DTs, found on a fossil flora or individual host plant) can all be measured. Three examples of responses of past plant-insect trophic interactions to environmental stresses are examined. In the first case study, late Oligocene fossil floras from Ethiopia document forest response to local perturbation and key characteristics to recognize disturbance in the plant fossil record. The second case study considers the terrestrial ecosystem response to the catastrophic global perturbation at the Cretaceous–Paleogene boundary. In the third case study, the impact of past global warming events—including the Paleocene–Eocene Thermal Maximum—on insect herbivory is discussed. Productive avenues for further research include: insect damage studies conducted outside the North American Cretaceous and Paleogene, actualistic and taphonomic studies of insect herbivory, and tighter collaboration across paleobotany, paleoentomology, botany, and entomology.

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Cleve, Keith Van, Walter C. Oechel et John L. Hom. « Response of black spruce (Piceamariana) ecosystems to soil temperature modification in interior Alaska ». Canadian Journal of Forest Research 20, n^o 9 (1 septembre 1990) : 1530–35. http://dx.doi.org/10.1139/x90-203.

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This paper reports results of a study designed to examine the control that soil temperature exerts on soil processes associated with nutrient flux, and in turn, on tree nutrition in interior Alaska black spruce ecosystems. Approximately 50 m2 of forest floor in a 140-year-old black spruce ecosystem, which had developed on permafrost, was heated to 8–10 °C above ambient temperature. This perturbation amounted to approximately a 1589 degree-day seasonal heat sum (above 0 °C), 1026 degree-days above the control total of 563 degree-days. The forest floor, surface 5 cm of mineral soil, and soil solution were compared with those of an adjacent control plot to evaluate the change in nutrient content and decomposition rate of the forest floor. The nutritional response to soil heating of current black spruce foliage also was evaluated. Soil heating significantly increased decomposition of the forest floor, principally because of an increase in biomass loss of the O21 layer. The increased decomposition resulted in greater extractable N and P concentrations in the forest floor, higher N concentrations in the soil solution, and elevated spruce needle N, P, and K concentrations for the experimental period. These results are discussed in light of the importance of soil temperature and other state factors that mediate ecosystem function.

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Fuentes, M. V., S. Sainz-Elipe, S. Sáez-Durán et M. T. Galán-Puchades. « The helminth community of the wood mouseApodemus sylvaticusin a Mediterranean ecosystem in regeneration ten years after a wildfire ». Journal of Helminthology 84, n^o 1 (7 juillet 2009) : 39–48. http://dx.doi.org/10.1017/s0022149x09990277.

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AbstractThis study was carried out 10 years after a wildfire in the Spanish Serra Calderona Natural Park, following a previous analysis comprising the first 5 years after the fire. Its primary aim was to elucidate the impact of this perturbation on the population biology of the wood mouseApodemus sylvaticus, and the repercussions on its helminth community in this regenerating Mediterranean ecosystem. Second, confirmation of the ability of the parasites to tolerate environmental stressors and the effects on their transmission strategies was sought. Five hundred and sixty-four individuals ofA. sylvaticuswere studied in a 9-year period, from the second to the tenth post-fire year: 408 mice from the burned area and 156 from the control – non-burned – area. The helminth community for both areas and the effect of intrinsic (host age and sex) and extrinsic (site, period and year of capture) factors on helminth prevalence, abundance and diversity, and species richness were analysed. Our findings show that, after an environmental disaster, the behaviour of helminth species might be related to their pre-catastrophe presence, their biological cycles, the host's immunological condition, the change of host dynamics, the direct effects of the perturbation, and the processes related to the re-establishment of the ecological balance of a devastated ecosystem.

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Dekker, S. C., H. J. de Boer, V. Brovkin, K. Fraedrich, M. J. Wassen et M. Rietkerk. « Biogeophysical feedbacks trigger shifts in the modelled climate system at multiple scales ». Biogeosciences Discussions 6, n^o 6 (25 novembre 2009) : 10983–1004. http://dx.doi.org/10.5194/bgd-6-10983-2009.

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Abstract. Terrestrial vegetation influences climate by modifying the radiative-, momentum-, and hydrologic-balance. This paper contributes to the ongoing debate on the question whether positive biogeophysical feedbacks between vegetation and climate may lead to multiple equilibria in vegetation and climate and consequent abrupt regime shifts. Several modelling studies argue that vegetation-climate feedbacks at local to regional scales could be strong enough to establish multiple states in the climate system. An Earth Model of Intermediate Complexity, PlaSim, is used to investigate the resilience of the climate system to vegetation disturbance at regional to global scales. We hypothesize that by starting with two extreme initialisations of biomass, positive vegetation-climate feedbacks will keep the vegetation-atmosphere system within different attraction domains. Indeed, model integrations starting from different initial biomass distributions diverged to clearly distinct climate-vegetation states in terms of abiotic (precipitation and temperature) and biotic (biomass) variables. Moreover, we found that between these states there are several other steady states which depend on the scale of perturbation. From here global susceptibility maps were made showing regions of low and high resilience. The model results suggest that mainly the boreal and monsoon regions have low resiliences, i.e. instable biomass equilibria, with positive vegetation-climate feedbacks in which the biomass induced by a perturbation is further enforced. The perturbation did not only influence single vegetation-climate cell interactions but also caused changes in spatial patterns of atmospheric circulation due to neighbouring cells constituting in spatial vegetation-climate feedbacks. Large perturbations could trigger an abrupt shift of the system towards another steady state. Although the model setup used in our simulation is rather simple, our results stress that the coupling of feedbacks at multiple scales in vegetation-climate models is essential and urgent to understand the system dynamics for improved projections of ecosystem responses to anthropogenic changes in climate forcing.

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Dekker, S. C., H. J. de Boer, V. Brovkin, K. Fraedrich, M. J. Wassen et M. Rietkerk. « Biogeophysical feedbacks trigger shifts in the modelled vegetation-atmosphere system at multiple scales ». Biogeosciences 7, n^o 4 (12 avril 2010) : 1237–45. http://dx.doi.org/10.5194/bg-7-1237-2010.

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Abstract. Terrestrial vegetation influences climate by modifying the radiative-, momentum-, and hydrologic-balance. This paper contributes to the ongoing debate on the question whether positive biogeophysical feedbacks between vegetation and climate may lead to multiple equilibria in vegetation and climate and consequent abrupt regime shifts. Several modelling studies argue that vegetation-climate feedbacks at local to regional scales could be strong enough to establish multiple states in the climate system. An Earth Model of Intermediate Complexity, PlaSim, is used to investigate the resilience of the climate system to vegetation disturbance at regional to global scales. We hypothesize that by starting with two extreme initialisations of biomass, positive vegetation-climate feedbacks will keep the vegetation-atmosphere system within different attraction domains. Indeed, model integrations starting from different initial biomass distributions diverged to clearly distinct climate-vegetation states in terms of abiotic (precipitation and temperature) and biotic (biomass) variables. Moreover, we found that between these states there are several other steady states which depend on the scale of perturbation. From here global susceptibility maps were made showing regions of low and high resilience. The model results suggest that mainly the boreal and monsoon regions have low resiliences, i.e. instable biomass equilibria, with positive vegetation-climate feedbacks in which the biomass induced by a perturbation is further enforced. The perturbation did not only influence single vegetation-climate cell interactions but also caused changes in spatial patterns of atmospheric circulation due to neighbouring cells constituting in spatial vegetation-climate feedbacks. Large perturbations could trigger an abrupt shift of the system towards another steady state. Although the model setup used in our simulation is rather simple, our results stress that the coupling of feedbacks at multiple scales in vegetation-climate models is essential and urgent to understand the system dynamics for improved projections of ecosystem responses to anthropogenic changes in climate forcing.

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Torre, I., A. Arrizabalaga, C. Feliu et A. Ribas. « The helminth infracommunities of the wood mouse (Apodemus sylvaticus) two years after the fire in Mediterranean forests ». Helminthologia 50, n^o 1 (1 mai 2013) : 27–38. http://dx.doi.org/10.2478/s11687-013-0104-8.

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AbstractParasites have been recognized as indicators for natural or man-induced environmental stress and perturbation. In this article, we investigated the role of two non-exclusive hypotheses on the response of helminths of wood mice to fire perturbation: 1) a reduction of the helminth infracommunity (species richness) in post-fire areas due to the temporal lack of worms with indirect (complex) life cycles linked to intermediate hosts that are more specialized than the final host, and 2) an increase of the abundance of helminths with direct (simple) life cycles as a response of increasing abundances of the final host, may be in stressful conditions linked to the post-fire recolonization process.We studied the helminth infracommunities of 97 wood mice in two recently burned plots (two years after the fire) and two control plots in Mediterranean forests of NE Spain. Species richness of helminths found in control plots (n = 14) was twice large than in burned ones (n = 7). Six helminth species were negatively affected by fire perturbation and were mainly or only found in unburned plots. Fire increased the homogeneity of helminth infracommunities, and burned plots were characterised by higher dominance, and higher parasitation intensity. We found a gradient of frequency of occurrence of helminth species according to life cycle complexity in burned areas, being more frequent monoxenous (66.6 %), than diheteroxenous (33.3 %) and triheteroxenous (0 %), confirming the utility of helminths as bioindicators for ecosystem perturbations. Despite the short period studied, our results pointed out an increase in the abundance and prevalence of some direct life cycle helminths in early postfire stages, whereas indirect life cycle helminths were almost absent. A mismatch between the final host (that showed a fast recovery shortly after the fire), and the intermediate hosts (that showed slow recoveries shortly after the fire), was responsible for the loss of half of the helminth species.

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Janzen, Daniel H., et Winnie Hallwachs. « To us insectometers, it is clear that insect decline in our Costa Rican tropics is real, so let’s be kind to the survivors ». Proceedings of the National Academy of Sciences 118, n^o 2 (11 janvier 2021) : e2002546117. http://dx.doi.org/10.1073/pnas.2002546117.

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We have been field observers of tropical insects on four continents and, since 1978, intense observers of caterpillars, their parasites, and their associates in the 1,260 km2 of dry, cloud, and rain forests of Área de Conservación Guanacaste (ACG) in northwestern Costa Rica. ACG’s natural ecosystem restoration began with its national park designation in 1971. As human biomonitors, or “insectometers,” we see that ACG’s insect species richness and density have gradually declined since the late 1970s, and more intensely since about 2005. The overarching perturbation is climate change. It has caused increasing ambient temperatures for all ecosystems; more erratic seasonal cues; reduced, erratic, and asynchronous rainfall; heated air masses sliding up the volcanoes and burning off the cloud forest; and dwindling biodiversity in all ACG terrestrial ecosystems. What then is the next step as climate change descends on ACG’s many small-scale successes in sustainable biodevelopment? Be kind to the survivors by stimulating and facilitating their owner societies to value them as legitimate members of a green sustainable nation. Encourage national bioliteracy, BioAlfa.

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Tan, Jianguo, Wenjuan Wang et Jianfeng Feng. « Transient Dynamics Analysis of a Predator-Prey System with Square Root Functional Responses and Random Perturbation ». Mathematics 10, n^o 21 (2 novembre 2022) : 4087. http://dx.doi.org/10.3390/math10214087.

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In this paper, we study the asymptotic and transient dynamics of a predator–prey model with square root functional responses and random perturbation. Firstly, the mean square stability matrix is obtained from the stability theory of stochastic systems, and three stability indexes (root-mean-square resilience, root-mean-square reactivity and root-mean-square amplification envelope) of the ecosystem response to stochastic disturbances are calculated. We find that: (1) no matter which population is disturbed, increasing the intensity of disturbance improves the ability of the system leaves steady state and thus decreases the stability. The root-mean-square amplification envelope rises with increasing disturbance intensity, (2) the system is more sensitive to the disturbance of the predator than disturbance to prey, (3) ρmax and tmax are important indicators, which represent the intensity and time of maximum amplification by disturbance. These findings are helpful for managers to take corresponding management measures to reduce the disturbances, especially for predators, thereby avoiding the possible change of the structure and functions of the ecosystem.

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Adam, Thomas C., Russell J. Schmitt, Sally J. Holbrook, Andrew J. Brooks, Peter J. Edmunds, Robert C. Carpenter et Giacomo Bernardi. « Herbivory, Connectivity, and Ecosystem Resilience : Response of a Coral Reef to a Large-Scale Perturbation ». PLoS ONE 6, n^o 8 (25 août 2011) : e23717. http://dx.doi.org/10.1371/journal.pone.0023717.

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Rice, Jake C. « A generalization of the three-stage model for advice using the precautionary approach in fisheries, to apply broadly to ecosystem properties and pressures ». ICES Journal of Marine Science 66, n^o 3 (21 février 2009) : 433–44. http://dx.doi.org/10.1093/icesjms/fsp021.

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AbstractRice, J. C. 2009. A generalization of the three-stage model for advice using the precautionary approach in fisheries, to apply broadly to ecosystem properties and pressures. – ICES Journal of Marine Science, 66: 433–444. The six assumptions of the three-stage model for fisheries advice using a precautionary approach are itemized. The general applicability of each is considered for use with any indicator of ecosystem status, or human pressure on the ecosystem indicator, rather than just spawning-stock biomass (SSB) and fishing mortality. The framework is fully generalizable, at least conceptually, without requiring additional assumptions or extensions that are less plausible than the assumptions already made in fisheries applications. However, application of the three-stage framework in fisheries hinges on the existence of some relationship between stock productivity and SSB as the basis for selecting a limit reference point and positioning a precautionary reference point. Three types of relationship can exist in fisheries data, and the framework has strategies for dealing with each. In an ecosystem application, the notion of a relationship between productivity and the amount of an ecosystem feature is sometimes appropriate, but sometimes the response variable may be resilience of the feature to perturbation or its ability to serve some ecosystem function as a function of the extent of the feature. The generalized framework accommodates all three types of response in five functional relationships, each of which can allow locating a candidate limit reference point.

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Mohamadkhani, Ashraf. « Gut Microbiota and Fecal Metabolome Perturbation in Children with Autism Spectrum Disorder ». Middle East Journal of Digestive Diseases 10, n^o 4 (21 juillet 2018) : 205–12. http://dx.doi.org/10.15171/mejdd.2018.112.

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The brain-intestinal axis concept describes the communication between the intestinal microbiota as an ecosystem of a number of dynamic microorganisms and the brain. The composition of the microbial community of the human gut is important for human health by influencing the total metabolomic profile. In children with autism spectrum disorder (ASD), the composition of the fecal microbiota and their metabolic products has a different configuration of the healthy child. An imbalance in the metabolite derived from the microbiota in children with ASD affect brain development and social behavior. In this article, we review recent discoveries about intestinal metabolites derived from microbiota based on high-yield molecular studies in children with ASD as part of the "intestinal brain axis".

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Pfefferkorn, Hermann W., Robert A. Gastaldo et William A. DiMichele. « Ecological Stability during the Late Paleozoic Cold Interval ». Paleontological Society Papers 6 (novembre 2000) : 63–78. http://dx.doi.org/10.1017/s1089332600000711.

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Ecosystem Stability and taxonomic stasis are the opposite aspect in the history of life from ecosystem perturbation and reorganization, or extinction and origination. Naturally, change is more exciting than stasis, and change also is more useful in many ways as, for instance, in the development of biostratigraphic frameworks. Paleontological preference for geologically rapid change has gone so far that a fast evolving group of organisms has been used to create an orthostratigraphy (Orthochronologie of Schindewolf, 1950), which is claimed to be the “real” biostratigraphy. By implication, all other taxonomic groups are relegated to a secondary status of merely delivering “parastratigraphies,” which may be useful (locally or regionally), but are not the “real thing.” Ammonites, conodonts, foraminifera, and a few other taxa hold the distinction of being the “chosen” taxa, and it should be self-evident that only marine organisms qualify for this role. On the other hand, organisms on land always have been known to demonstrate coarser stratigraphic resolution. By implication, they might be more prone to ecosystem and taxonomic stasis over the long run. This, in itself, is an important observation.

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Tan, Xuewen, Wenjie Qin, Guangyao Tang, Changcheng Xiang et Xinzhi Liu. « Models to Assess the Effects of Nonsmooth Control and Stochastic Perturbation on Pest Control : A Pest-Natural-Enemy Ecosystem ». Complexity 2019 (14 avril 2019) : 1–14. http://dx.doi.org/10.1155/2019/8326164.

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This paper investigates the impact of the threshold control strategy and environmental randomness on pest control. Firstly, a fixed-time impulsive stochastic ecosystem with IPM strategy is proposed, where the local and global existence of positive solution and the boundedness of expectation are discussed in detail. Moreover a sufficient condition for the extinction of the pest population with probability-1 is given. Then, a state-dependent stochastic ecosystem with IPM strategy is proposed. By employing the numerical simulations, the effects of ambient noise intensity on pest-outbreak are discussed. The result shows that there is a close relationship among the frequency of pest-outbreak, ET, the environmental perturbation intensity, and control measures. This study helps us to understand the impact of random factors on pest-outbreak frequency by theoretical derivations and numerical simulations; the results have directive significance in the design of an optimal control strategy for the department of ecological agriculture.

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