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Berlin Brandenburg

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  • 1
    In: Oikos, October 2014, Vol.123(10), pp.1224-1233
    Description: Soil systems maintain important ecosystem processes crucial for plant life and food production. Especially agricultural systems are strongly affected by climate change due to low vegetation cover associated with high temperatures and drought. Nevertheless, the response of soil systems to climate change is little explored. We used microcosms with a simplified soil community to address effects of climate change using independent temperature and dryness gradients and addressed their effects on top–down control and litter decomposition. The community consisted of maize litter as a basal resource, fungi, springtails and as top predators mites and centipedes. As the body‐size structure is of high importance for communities, we included differently‐sized springtails and predator species. After seven weeks, the experiment was terminated, and the impact of climate change on direct feeding interactions and indirect effects across trophic levels was analysed. With increasing temperature and dryness, consumption rates increased, thereby amplifying the negative influence of consumer populations on their resources. Hence, these climate‐change variables increased the top–down control of 1) predators (mainly mites) on springtails and 2) fungi on litter decomposition. In addition, we found that the climate‐change variables strengthened trophic cascades from predators on fungi whose density was thus increasingly decoupled from top–down control by their springtail consumers. Their increased decomposition rates are of high importance for carbon cycling and may result in accelerated nutrient turnover. In conclusion, our results suggest that climate change may strongly influence the structure and functioning of soil systems by strengthening consumption rates and trophic cascades, which will have far reaching consequences for the nutrient turnover and productivity of agricultural ecosystems.
    Keywords: Climate Change – Environmental Aspects ; Droughts – Environmental Aspects ; Agricultural Ecology – Environmental Aspects ; Ecosystems – Environmental Aspects;
    ISSN: 0030-1299
    E-ISSN: 1600-0706
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  • 2
    In: Oikos, October 2014, Vol.123(10), pp.1192-1198
    Description: Predation is an important ecological factor driving animal population structures, community assemblages and consequently ecosystem stability and biodiversity. Many environmental factors influence direction and intensity of predation, suggesting that trophic linkages between animals vary between different habitats. This in consequence has particular relevance in anthropogenically altered habitats such as managed forests, where disturbance regime, tree composition and stand age may change the natural food web structure. We investigated how prey consumption of three common centipede predators ( spp., Chilopoda), representing two body sizes varies between four differently managed forest types in two regions across Germany. We hypothesized that prey preference of these generalist predators is independent of forest type but rather driven by habitat structure, prey abundance and predator body size. Applying specific PCR assays to test for DNA of three abundant prey groups, i.e. Collembola, Diptera and Lumbricidae, in the predators’ guts, we tracked trophic interactions. The results showed that management type indeed has no influence on centipede prey consumption but depth of litter layer and soil pH. Trophic interactions varied between the two sampled forests regions mainly due to changes in the detection of Lumbricidae and Diptera. Also, effect of litter layer and prey abundance significantly differed between the smaller and the larger , indicating a body size effect. The results complement food web analyses using fatty acids and stable isotopes by elucidating trophic interactions in soil in unprecedented detail.
    Keywords: Genetic Research – Analysis ; Forest Soils – Analysis ; Ecosystems – Analysis;
    ISSN: 0030-1299
    E-ISSN: 1600-0706
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  • 3
    In: Ecology Letters, October 2011, Vol.14(10), pp.993-1000
    Description: For more than a century, the scaling of animal metabolic rates with individual body masses and environmental temperature has predominantly been described by power-law and exponential relationships respectively. Many theories have been proposed to explain these scaling relationships, but were challenged by empirically documented curvatures on double-logarithmic scales. In the present study, we present a novel data set comprising 3661 terrestrial (mainly soil) invertebrate respiration rates from 192 independent sources across a wide range in body masses, environmental temperatures and phylogenetic groups. Although our analyses documented power-law and exponential scaling with body masses and temperature, respectively, polynomial models identified curved deviations. Interestingly, complex scaling models accounting for phylogenetic groups were able to remove curvatures except for a negative curvature at the highest temperatures (〉30 degree C) indicating metabolic down regulation. This might indicate that the tremendous differences in invertebrate body architectures, ecology and physiology may cause severely different metabolic scaling processes.Original Abstract: Ecology Letters (2011) 14: 993-1000
    Keywords: Body Mass ; Curvature ; Invertebrate ; Metabolic Rate ; Mte ; Phylogenetic Group ; Polynomial ; Respiration ; Temperature
    ISSN: 1461-023X
    E-ISSN: 1461-0248
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  • 4
    Language: English
    In: Global change biology, 2011, Vol.17(3), pp.1301-1310
    Description: Predictions on the consequences of the rapidly increasing atmospheric CO₂ levels and associated climate warming for population dynamics, ecological community structure and ecosystem functioning depend on mechanistic energetic models of temperature effects on populations and their interactions. However, such mechanistic approaches combining warming effects on metabolic (energy loss of organisms) and feeding rates (energy gain by organisms) remain a key, yet elusive, goal. Aiming to fill this void, we studied the metabolic rates and functional responses of three differently sized, predatory ground beetles on one mobile and one more resident prey species across a temperature gradient (5, 10, 15, 20, 25 and 30 °C). Synthesizing metabolic and functional-response theory, we develop novel mechanistic predictions how predator-prey interaction strengths (i.e., functional responses) should respond to warming. Corroborating prior theory, warming caused strong increases in metabolism and decreases in handling time. Consistent with our novel model, we found increases in predator attack rates on a mobile prey, whereas attack rates on a mostly resident prey remained constant across the temperature gradient. Together, these results provide critically important information that environmental warming generally increases the direct short-term per capita interaction strengths between predators and their prey as described by functional-response models. Nevertheless, the several fold stronger increase in metabolism with warming caused decreases in energetic efficiencies (ratio of per capita feeding rate to metabolic rate) for all predator-prey interactions. This implies that warming of natural ecosystems may dampen predator-prey oscillations thus stabilizing their dynamics. The severe long-term implications; however, include predator starvation due to energetic inefficiency despite abundant resources. ; Includes references ; p. 1301-1310.
    Keywords: Global Warming -- Statistics ; Global Warming -- Analysis ; Beetles -- Statistics ; Beetles -- Analysis ; Ecosystems -- Statistics ; Ecosystems -- Analysis;
    ISSN: 1354-1013
    E-ISSN: 13652486
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  • 5
    In: Journal of Ecology, May 2012, Vol.100(3), pp.597-604
    Description:  Rhizosphere bacteria antagonistic to fungal pathogens improve plant performance by preventing infection. In temperate grasslands, primary productivity often increases with plant diversity, and we hypothesized that this effect may in part rely on the interactions between plants and antagonistic bacteria.  We investigated the impact of plant diversity and functional group composition on soil bacteria producing the antifungal compounds 2,4‐diacetylphloroglucinol (DAPG) and pyrrolnitrin (PRN) in a long‐term grassland biodiversity experiment, as well as their impact on soil suppressiveness. Soil suppressiveness was investigated in a model infection assay with and the pathogen .  The abundance of DAPG and PRN producers increased with plant diversity and that of PRN also increased in the presence of grasses. Moreover, legume species richness and coverage decreased the abundance of DAPG and PRN producers, respectively, contrary to beneficial effects of legumes on soil microorganisms reported previously. In turn, soil suppressiveness was at maximum when DAPG and PRN producer abundance was high.   Our results suggest that plant diversity contributes to plant community resistance against pathogens by fostering beneficial bacterial communities. This indirect soil feedback mechanism may contribute to the positive relationship between plant diversity and productivity and could also help the development of more sustainable and environmentally friendly agricultural management strategies. Our results suggest that plant diversity contributes to plant community resistance against pathogens by fostering beneficial bacterial communities. This indirect soil feedback mechanismmay contribute to the positive relationship between plant diversity and productivity and could also help the development of more sustainable and environmentally friendly agricultural management strategies.
    Keywords: 2 ; 4‐Diacetylphloroglucinol ; Biodiversity–Ecosystem Functioning Relationship ; Plant–Microbe Interactions ; Plant–Soil Below‐Ground Interactions ; Pseudomonas Fluorescens ; Pyrrolnitrin ; Soil Feedbacks ; Soil Suppressiveness
    ISSN: 0022-0477
    E-ISSN: 1365-2745
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  • 6
    In: Oikos, December 2017, Vol.126(12), pp.1717-1725
    Description: With the world continuously warming, a mechanistic understanding of how temperature affects interaction strengths, which are fundamental to food‐web stability, is needed. As interaction strengths are determined by the flows of energy from resources to consumers, we investigated effects of temperature on animal energetics. We used newly compiled datasets on respiration rates and assimilation efficiencies to assess how temperature affects the energy use (respiration rates) and the efficiency of energy gain (assimilation efficiency) for different consumer types. Furthermore, we incorporated our findings in a simulation of temperature effects on maintenance feeding rates (i.e. energy consumption necessary to sustain life). Our analysis revealed a generally positive temperature dependence of assimilation efficiencies across consumer types thus implying a net energy gain with warming. The temperature scaling of respiration rates did not differ between consumer types. Based on these parameters we calculated maintenance feeding rates and compared them to empirically measured (realized) feeding rates. This comparison revealed that detritivores and herbivores have the potential to increase their biomasses under warming as their maintenance feeding rates increase less strongly than their realized feeding rates. For carnivores, however, we found a stronger increase of their maintenance feeding rates compared to their realized feeding rates, which should lead to decreased population sizes under warming. Overall, our results increase the understanding of climate change effects on ecosystems as they suggest profound energetic consequences for natural communities.
    Keywords: Energy Consumption – Analysis ; Climate Change – Analysis;
    ISSN: 0030-1299
    E-ISSN: 1600-0706
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  • 7
    In: Oikos, July 2018, Vol.127(7), pp.915-926
    Description: Analysis of predator–prey interactions is a core concept of animal ecology, explaining structure and dynamics of animal food webs. Measuring the functional response, i.e. the intake rate of a consumer as a function of prey density, is a powerful method to predict the strength of trophic links and assess motives of prey choice, particularly in arthropod communities. However, due to their reductionist set‐up, functional responses, which are based on laboratory feeding experiments, may not display field conditions, possibly leading to skewed results. Here, we tested the validity of functional responses of centipede predators and their prey by comparing them with empirical gut content data from field‐collected predators. Our predator–prey system included lithobiid and geophilomorph centipedes, abundant and widespread predators of forest soils and their soil‐dwelling prey. First, we calculated the body size‐dependent functional responses of centipedes using a published functional response model in which we included natural prey abundances and animal body masses. This allowed us to calculate relative proportions of specific prey taxa in the centipede diet. In a second step, we screened field‐collected centipedes for DNA of eight abundant soil‐living prey taxa and estimated their body size‐dependent proportion of feeding events. We subsequently compared empirical data for each of the eight prey taxa, on proportional feeding events with functional response‐derived data on prey proportions expected in the gut, showing that both approaches significantly correlate in five out of eight predator–prey links for lithobiid centipedes but only in one case for geophilomorph centipedes. Our findings suggest that purely allometric functional response models, which are based on predator–prey body size ratios are too simple to explain predator–prey interactions in a complex system such as soil. We therefore stress that specific prey traits, such as defence mechanisms, must be considered for accurate predictions.
    Keywords: Allometric Scaling ; Generalist Predator ; Molecular Prey Detection ; Predator–Prey Interaction
    ISSN: 0030-1299
    E-ISSN: 1600-0706
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  • 8
    In: Oikos, April 2018, Vol.127(4), pp.590-598
    Description: Empirical feeding studies where density‐dependent consumption rates are fitted to functional response models are often used to parameterize the interaction strengths in models of population or food‐web dynamics. However, the relationship between functional response parameter estimates from short‐term feeding studies and real‐world, long‐term, trophic interaction strengths remains largely unexamined. In a critical first step to address this void, we tested for systematic effects of experimental duration and predator satiation on the estimate of functional response parameters, namely attack rate and handling time. Analyzing a large data set covering a wide range of predator taxa and body masses, we show that attack rates decrease with increasing experimental duration, and that handling times of starved predators are consistently shorter than those of satiated predators. Therefore, both the experimental duration and the predator satiation level have a strong and systematic impact on the predictions of population dynamics and food‐web stability. Our study highlights potential pitfalls at the intersection of empirical and theoretical applications of functional responses. We conclude our study with some practical suggestions for how these implications should be addressed in the future to improve predictive abilities and realism in models of predator–prey interactions.
    Keywords: Environmental Sciences ; Biology ; Ecology;
    ISSN: 0030-1299
    E-ISSN: 1600-0706
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  • 9
    In: Global Change Biology, January 2016, Vol.22(1), pp.220-227
    Description: Warming and eutrophication are two of the most important global change stressors for natural ecosystems, but their interaction is poorly understood. We used a dynamic model of complex, size‐structured food webs to assess interactive effects on diversity and network structure. We found antagonistic impacts: Warming increases diversity in eutrophic systems and decreases it in oligotrophic systems. These effects interact with the community size structure: Communities of similarly sized species such as parasitoid–host systems are stabilized by warming and destabilized by eutrophication, whereas the diversity of size‐structured predator–prey networks decreases strongly with warming, but decreases only weakly with eutrophication. Nonrandom extinction risks for generalists and specialists lead to higher connectance in networks without size structure and lower connectance in size‐structured communities. Overall, our results unravel interactive impacts of warming and eutrophication and suggest that size structure may serve as an important proxy for predicting the community sensitivity to these global change stressors.
    Keywords: Complex Food Webs ; Extinctions ; Generalists ; Global Change ; Size Structure ; Specialists
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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  • 10
    In: Journal of Animal Ecology, May 2012, Vol.81(3), pp.516-523
    Description:  Model analyses show that the stability of population dynamics and food web persistence increase with the strength of interference competition. Despite this critical importance for community stability, little is known about how external factors such as the environmental temperature affect intraspecific interference competition.  We aimed to fill this void by studying the functional responses of two ground beetle species of different body size, and . These functional response experiments were replicated across four predator densities and two temperatures to address the impact of temperature on intraspecific interference competition.  We generally expected that warming should increase the speed of movement, encounter rates and in consequence interference among predator individuals. In our experiment, this expectation was supported by the results obtained for the larger predator, , whereas the opposite pattern characterized the interference behaviour of the smaller predator  These results suggest potentially nontrivial implications for the effects of environmental temperature on intraspecific interference competition, for which we propose an explanation based on the different sensitivity to warming of metabolic rates of both species. As expected, increasing temperature led to stronger interference competition of the larger species, , which exhibited a weaker increase in metabolic rate with increasing temperature. The stronger increase in the metabolic rate of the smaller predator, , had to be compensated by increasing searching activity for prey, which did not leave time for increasing interference.  Together, these results suggest that any generalization how interference competition responds to warming should also take the species’ metabolic response to temperature increases into account.
    Keywords: Food Webs ; Functional Responses ; Global Warming ; Interaction Strength ; Metabolic Rates
    ISSN: 0021-8790
    E-ISSN: 1365-2656
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