scholarly journals Pyramids and cascades: a synthesis of food chain functioning and stability

2018 ◽  
Author(s):  
Matthieu Barbier ◽  
Michel Loreau
Keyword(s):  
Food Chain ◽  
Trophic Cascade ◽  
Self Regulation ◽  
Quantitative Comparison ◽  
Food Chains ◽  
Fragmented Landscape ◽  
Size Spectra ◽  
Predator Prey ◽  
Theoretical Predictions ◽  
Chain Theory

AbstractFood chain theory is one of the cornerstones of ecology, providing many of its basic predictions, such as biomass pyramids, trophic cascades and predator-prey oscillations. Yet, ninety years into this theory, the conditions under which these patterns may occur and persist in nature remain subject to debate. Rather than address each pattern in isolation, we propose that they must be understood together, calling for synthesis in a fragmented landscape of theoretical and empirical results. As a first step, we propose a minimal theory that combines the long-standing energetic and dynamical approaches of food chains. We chart theoretical predictions on a concise map, where two main regimes emerge: across various functioning and stability metrics, one regime is characterized by pyramidal patterns, the other by cascade patterns. The axes of this map combine key physiological and ecological variables, such as metabolic rates and self-regulation. A quantitative comparison with data sheds light on conflicting theoretical predictions and empirical puzzles, from size spectra to causes of trophic cascade strength. We conclude that drawing systematic connections between various existing approaches to food chains, and between their predictions on functioning and stability, is a crucial step in confronting this theory to real ecosystems.

scholarly journals Metapopulation capacity determines food chain length in fragmented landscapes

2021 ◽  
Vol 118 (34) ◽  
pp. e2102733118
Author(s):  
Shaopeng Wang ◽  
Ulrich Brose ◽  
Saskya van Nouhuys ◽  
Robert D. Holt ◽  
Michel Loreau
Keyword(s):  
Chain Length ◽  
Food Chain ◽  
Landscape Configuration ◽  
Food Chains ◽  
Fragmented Landscape ◽  
Fragmented Landscapes ◽  
Habitat Changes ◽  
Food Chain Length ◽  
Multispecies Systems ◽  
The Impact

Metapopulation capacity provides an analytic tool to quantify the impact of landscape configuration on metapopulation persistence, which has proven powerful in biological conservation. Yet surprisingly few efforts have been made to apply this approach to multispecies systems. Here, we extend metapopulation capacity theory to predict the persistence of trophically interacting species. Our results demonstrate that metapopulation capacity could be used to predict the persistence of trophic systems such as prey–predator pairs and food chains in fragmented landscapes. In particular, we derive explicit predictions for food chain length as a function of metapopulation capacity, top-down control, and population dynamical parameters. Under certain assumptions, we show that the fraction of empty patches for the basal species provides a useful indicator to predict the length of food chains that a fragmented landscape can support and confirm this prediction for a host–parasitoid interaction. We further show that the impact of habitat changes on biodiversity can be predicted from changes in metapopulation capacity or approximately by changes in the fraction of empty patches. Our study provides an important step toward a spatially explicit theory of trophic metacommunities and a useful tool for predicting their responses to habitat changes.

scholarly journals THE EFFECT OF SELENIUM ON MERCURY TRANSPORT ALONG THE FOOD CHAIN

AGROFOR ◽  
2016 ◽  
Vol 1 (3) ◽  
Author(s):  
Primož ZIDAR ◽  
Špela KRŽIŠNIK ◽  
Marta DEBELJAK ◽  
Suzana ŽIŽEK ◽  
Katarina VOGEL MIKUŠ
Keyword(s):  
Food Chain ◽  
Contaminated Soil ◽  
Local Population ◽  
Trophic Levels ◽  
Food Chains ◽  
Chemical Transformations ◽  
Soil Concentration ◽  
Preliminary Results ◽  
Mercury Transport ◽  
Hg Accumulation

More than 500 years of mercury (Hg) production in Idrija (Slovenia) resulted in aconsiderable pollution of Idrija region with Hg. Although the mine is closed formore than 20 years, the total soil concentration of Hg may still reach up to severalhundred mgkg-1dry weightin local gardens and more that thousand inother urbanregions. Hg in soil undergoesdifferent chemical transformations and in someformsit may enterplants and higher trophic levelsin food chains, also withbiomagnification pattern.The local population is, besides air and dust, thus exposedto mercury also via consumption of locally produced food.Several studies showedthat the increased level of selenium in soil may reduce the uptake of mercury inplants but very few include other trophic levels in a food chain as well.In our pilotstudy we followed an impact of Seon Hg transport from soil to plants(Lactucasativa) and further to soil dwelling animals (Porcellioscaber). Lettuce wasplanted in a contaminated soil from Idrija and in soil with added HgCl2. The leavesof half of the plants weresprayed with Sesolution (5μg L-1)threeand five weeksafter planting.After six weeks plants were analyzed for Hg and Se and offered asfood to terrestrial isopods for two weeks. Our preliminary results revealed thatfoliar treatment of plants with Se may affect Hg accumulation in plants andtherefore further transport of Hg across the food chain.

scholarly journals On mechanisms of trophic cascade caused by anti-predation response in food chain systems

2020 ◽  
Vol 1 (2) ◽  
pp. 1-27
Author(s):  
Yang Wang ◽  
Xingfu Zou
Keyword(s):  
Food Chain ◽  
Trophic Cascade ◽  
Predation Rate ◽  
Model Systems ◽  
Large Carnivores ◽  
Response Level ◽  
Population Sizes ◽  
The Cost ◽  
The Impact ◽  
D Model

Motivated by a recent field study [Nat. Commun. 7(2016), 10698] on the impact of fear of large carnivores on the populations in a cascading ecosystem of food chain type with the large carnivores as the top predator, in this paper we propose two model systems in the form of ordinary differential equations to mechanistically explore the cascade of such a fear effect. The models are of the Lotka-Volterra type, one is three imensional and the other four dimensional. The 3-D model only considers the cost of the anti-predation response reflected in the decrease of the production, while the 4-D model considers also the benefit of the response in reducing the predation rate, in addition to the cost by reducing the production. We perform a thorough analysis on the dynamics of the two models. The results reveal that the 3-D model and 4-model demonstrate opposite patterns for trophic cascade in terms of the dependence of population sizes for each species at the co-existence equilibrium on the anti-predation response level parameter, and such a difference is attributed to whether or not there is a benefit for the anti-predation response by the meso-carnivore species.

scholarly journals A Quantitative Comparison of Exoplanet Catalogs

Geosciences ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 325 ◽  
Author(s):  
Dolev Bashi ◽  
Ravit Helled ◽  
Shay Zucker
Keyword(s):  
Careful Analysis ◽  
Quantitative Comparison ◽  
Mass Temperature ◽  
Theoretical Predictions ◽  
Kolmogorov Smirnov ◽  
Statistical Studies ◽  
Stellar Properties ◽  
Ks Test ◽  
Good Agreement

In this study, we investigated the differences between four commonly-used exoplanet catalogs (exoplanet.eu; exoplanetarchive.ipac.caltech.edu; openexoplanetcatalogue.com; exoplanets.org) using a Kolmogorov–Smirnov (KS) test. We found a relatively good agreement in terms of the planetary parameters (mass, radius, period) and stellar properties (mass, temperature, metallicity), although a more careful analysis of the overlap and unique parts of each catalog revealed some differences. We quantified the statistical impact of these differences and their potential cause. We concluded that although statistical studies are unlikely to be significantly affected by the choice of catalog, it would be desirable to have one consistent catalog accepted by the general exoplanet community as a base for exoplanet statistics and comparison with theoretical predictions.

The transfer of65Zn and 59Fe along a Fucus serratus (L.)→ Littorina obtusata (L.) food chain

1975 ◽  
Vol 55 (3) ◽  
pp. 583-610 ◽  
Author(s):  
M. L. Young
Keyword(s):  
Trace Metals ◽  
Radiation Exposure ◽  
Marine Environment ◽  
Food Chain ◽  
Sea Water ◽  
Food Chains ◽  
Fresh Weight ◽  
Littorina Obtusata ◽  
Fucus Serratus ◽  
Marine Food

In marine organisms the fresh-weight concentrations of the trace metals zinc and iron are 102–105 times the concentrations in sea water. Study of the transfer of these metals along marine food chains is of interest because of the possibility of their being pollutants of the marine environment. Also65Zn and 65Fe are released to the marine environment and have been found, in many instances, to be the predominant radionuclides in food chains leading to man (Lowman, Palumbo & South, 1957; Lowman, 1960; Osterberg, Pearcy & Curl, 1964; Preston, 1967). The transfer of these metals along marine food chains is thus of interest also in the context of human radiation exposure.

scholarly journals Stability and Hopf Bifurcation of Delayed Predator-Prey System Incorporating Harvesting

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Fengying Wei ◽  
Lanqi Wu ◽  
Yuzhi Fang
Keyword(s):  
Hopf Bifurcation ◽  
Center Manifold ◽  
Hopf Bifurcations ◽  
Normal Form Theory ◽  
Predator Prey ◽  
Center Manifold Theorem ◽  
Prey System ◽  
Theoretical Predictions ◽  
Form Theory ◽  
The Stability

A kind of delayed predator-prey system with harvesting is considered in this paper. The influence of harvesting and delay is investigated. Our results show that Hopf bifurcations occur as the delayτpasses through critical values. By using of normal form theory and center manifold theorem, the direction of Hopf bifurcation and the stability of the bifurcating periodic solutions are obtained. Finally, numerical simulations are given to support our theoretical predictions.

Comparison and utility of different size-based metrics of fish communities for detecting fishery impacts

2006 ◽  
Vol 63 (4) ◽  
pp. 810-820 ◽  
Author(s):  
Daniel E Duplisea ◽  
Martin Castonguay
Keyword(s):  
Standing Stock ◽  
Fish Communities ◽  
Ecosystem Approach ◽  
Size Spectrum ◽  
Size Spectra ◽  
Predator Prey ◽  
Similar Information ◽  
Chance Events ◽  
Length Frequency Analysis ◽  
Scientific Survey

The use of fish community indicators based on size spectra has become popular in the development of an ecosystem approach to fisheries. Size spectrum theory arose from basic ecological work on energy flow, predator–prey interactions, and biomass standing stock and was later applied to fish communities as length–frequency analysis. A multitude of size spectrum indicators have resulted, but it is not clear if they all present similar information. Here we develop a simple framework describing what four size spectra indicators suggest about fish communities, their likely response to fisheries exploitation, their ecological interpretation, and some of their biases. We examined indicators for scientific survey data from six exploited North Atlantic fish communities for the information that they reveal about each community. Each indicator revealed different information and had different biases. Combining indicators for the most impacted system (owing to fisheries and environmental change), the eastern Scotian Shelf, revealed a pattern analogous to Holling's ecological cycle of exploitation, conservation, release, and reorganisation. If this analogy is generally valid, then it suggests that collapsed fish communities are more susceptible to chance events, and recovery is not directly reversible and may not be recoverable (to previous known state) at all if the system moves to an alternative cycle.

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