Ecosystems Ecology

Where do Cats Go?: Reflections on Death Post Patriarchal Christianity by Sara Frykenberg

by Feminism and Religion

Originally posted on the Feminism and Religion project.

The reason I am speaking about death today is two-fold.  First, I have been somewhat preoccupied with the concept... more The reason I am speaking about death today is two-fold.  First, I have been somewhat preoccupied with the concept of death since entering a new decade of my life.  I no longer believe in the evangelical vision of heaven I learned about in my youth; but as an uncomfortable “un”-Christian, I also have no satisfactory vision to replace it.  Or rather, there are many visions I find appealing, but none that I “believe in,” as I had believed in heaven.  My family is getting older, my parents have been sick in the last few years, and I often feel that I have more to lose now than I used to.

My second reason for considering death today is that last Wednesday, Mimi, our family cat of 24 years—yes, 24—passed away.  After spending all nine of her lives living, Mimi could no longer eat and was suffering.  My mother had her put down after we all said goodbye; we held a funeral for her and buried her among the lilies in our yard, her home.

Ecosystem restoration with teeth: what role for predators?

by Euan Ritchie

Recent advances highlight the potential for predators to restore ecosystems and confer resilience against globally... more Recent advances highlight the potential for predators to restore ecosystems and confer resilience against globally threatening processes, including climate change and biological invasions. However, releasing the ecological benefits of predators entails significant challenges. Here, we discuss the economic, environmental and social considerations affecting predator-driven ecological restoration programmes, and suggest approaches for reducing the undesirable impacts of predators. Because the roles of predators are context dependent, we argue for increased emphasis on predator functionality in ecosystems and less on the identities and origins of species and genotypes. We emphasise that insufficient attention is currently given to the importance of variation in the social structures and behaviours of predators in influencing the dynamics of trophic interactions. Lastly, we outline experiments specifically designed to clarify the ecological roles of predators and their potential utility in ecosystem restoration.

Consistent temperature dependence of respiration across ecosystems contrasting in thermal history

by Dan Perkins

Ecosystem respiration is a primary component of the carbon cycle and understanding the mechanisms that determine its... more Ecosystem respiration is a primary component of the carbon cycle and understanding the mechanisms that determine its temperature dependence will be important for predicting how rates of carbon efflux might respond to global warming. We used a rare model system, comprising a network of geothermally heated streams ranging in temperature from 5 °C to 25 °C, to explore the nature of the relationship between respiration and temperature. Using this ‘natural experiment’, we tested whether the natal thermal regime of stream communities influenced the temperature dependence of respiration in the absence of other potentially confounding variables. An empirical survey of 13 streams across the thermal gradient revealed that the temperature dependence of whole-stream respiration was equivalent to the average activation energy of the respiratory complex (0.6–0.7 eV). This observation was also consistent for in-situ benthic respiration. Laboratory experiments, incubating biofilms from four streams across the thermal gradient at a range of temperatures, revealed that the activation energy and Q10 of respiration were remarkably consistent across streams, despite marked differences in their thermal history and significant turnover in species composition. Furthermore, absolute rates of respiration at standardised temperature were also unrelated to ambient stream temperature, but strongly reflected differences in biofilm biomass. Together, our results suggest that the core biochemistry,which drives the kinetics of oxidative respiratory metabolism, may be well conserved among diverse taxa and environments, and that the intrinsic sensitivity of respiration to temperature is not influenced by ambient environmental temperature.

Warming alters the metabolic balance of ecosystems

by Gabriel Yvon-Durocher

The carbon cycle modulates climate change, via the regulation of atmospheric CO2, and it represents one of the most... more The carbon cycle modulates climate change, via the regulation of atmospheric CO2, and it represents one of the most important services provided by ecosystems. However, considerable uncertainties remain concerning potential feedback between the biota and the climate. In particular, it is unclear how global warming will affect the metabolic balance between the photosynthetic fixation and respiratory release of CO2 at the ecosystem scale. Here, we present a combination of experimental field data from freshwater mesocosms, and theoretical predictions derived from the metabolic theory of ecology to investigate whether warming will alter the capacity of ecosystems to absorb CO2. Our manipulative experiment simulated the temperature increases predicted for the end of the century and revealed that ecosystem respiration increased at a faster rate than primary production, reducing carbon sequestration by 13 per cent. These results confirmed our theoretical predictions based on the differential activation energies of these two processes. Using only the activation energies for whole ecosystem photosynthesis and respiration we provide a theoretical prediction that accurately quantified the precise magnitude of the reduction in carbon sequestration observed experimentally. We suggest the combination of whole-ecosystem manipulative experiments and ecological theory is one of the most promising and fruitful research areas to predict the impacts of climate change on key ecosystem services.

The Temperature Dependence of the Carbon Cycle in Aquatic Ecosystems

by Gabriel Yvon-Durocher

The carbon cycle modulates climate change via the regulation of atmospheric CO2, and represents one of the most... more The carbon cycle modulates climate change via the regulation of atmospheric CO2, and represents one of the most important ecosystem services of value to humans. However, considerable uncertainties remain concerning potential feedbacks between the biota and the climate. We developed theoretical models
derived from the metabolic theory of ecology (MTE), and tested them in an ecosystem-level manipulative experiment in freshwater mesocosms. The yearlong experiment simulated a warming scenario (A1B; [IPCC, 2007]) expected by the end of the century. The key components of the carbon cycle – that is gross primary production (GPP), ecosystem respiration (ER) and CH4 efflux (ME) – measured in our experiment were all strongly related to temperature. Their temperature dependence was typically constrained by the average activation energy of their particular metabolic pathway, and as predicted by our models, this increased progressively for GPP, ER and ME. Warming of 4°C decreased the sequestration of CO2 by 13%, increased the fraction of primary production effluxing as methane by 20% and the fraction of ER as methane by 9%, in line with the offset in their respective activation energies. Because methane has 21 times the greenhouse gas radiative potential of CO2, these results suggest aquatic ecosystems could drive a previously unknown positive feedback between warming and the carbon cycle.

We then used a series of global data compilations of measurements of rates of primary production and respiration to better understand the temperature dependence of the carbon cycle in other aquatic ecosystems and to compare them with data from terrestrial systems. Our experimental results were mirrored by our global data compilations, with the effective activation energy for marine and freshwater primary production identical to GPP measured in our experiment. Similarly, the temperature dependences of respiration in estuaries, lakes and the ocean were indistinguishable from that of ER in our experiment. Finally, our study suggests that the temperature dependence of primary production and respiration in aquatic ecosystems might differ from those in terrestrial ecosystems, and this could be crucial in predicting the future response of the carbon cycle in these different systems to global warming.

Warming increases the proportion of primary production emitted as methane from freshwater mesocosms

by Gabriel Yvon-Durocher

Methane (CH4) and carbon dioxide (CO2) are the dominant gaseous end products of the remineralization of organic carbon... more Methane (CH4) and carbon dioxide (CO2) are the dominant gaseous end products of the remineralization of organic carbon and also the two largest contributors to the anthropogenic greenhouse effect. We investigated whether warming altered the balance of CH4 efflux relative to gross primary production (GPP) and ecosystem respiration (ER) in a freshwater mesocosm experiment. Whole ecosystem CH4 efflux was strongly related to temperature with an apparent activation energy of 0.85 eV. Furthermore, CH4 efflux increased faster than ER or GPP with temperature, with all three processes having sequentially lower activation energies. Warming of 4C increased the fraction of GPP effluxing as CH4 by 20% and the fraction of ER as CH4 by 9%, in line with the offset in their respective activation energies. Because CH4 is 21 times more potent as a greenhouse gas, relative to CO2, these results suggest freshwater ecosystems could drive a previously unknown positive feedback between warming and the carbon cycle.

Warming alters the size spectrum and shifts the distribution of biomass in freshwater ecosystems

by Gabriel Yvon-Durocher

Organism size is one of the key determinants of community structure, and its relationship with abundance can describe... more Organism size is one of the key determinants of community structure, and its relationship with abundance can describe how biomass is partitioned among the biota within an ecosystem. An outdoor freshwater mesocosm experiment was used to determine how warming of 4°C would affect the size, biomass and taxonomic structure of planktonic communities. Warming increased the steepness of the community size spectrum by increasing the prevalence of small organisms, primarily within the phytoplankton assemblage and it also reduced the mean and maximum size of phytoplankton by approximately one order of magnitude. The observed shifts in phytoplankton size structure were reflected in changes in phytoplankton community composition, though zooplankton taxonomic composition was unaffected by warming. Furthermore, warming reduced community biomass and total phytoplankton biomass, although zooplankton biomass was unaffected. This resulted in an increase in the zooplankton to phytoplankton biomass ratio in the warmed mesocosms, which could be explained by faster turnover within the phytoplankton assemblages. Overall, warming shifted the distribution of phytoplankton size towards smaller individuals with rapid turnover and low standing biomass, resulting in a reorganization of the biomass structure of the food webs. These results indicate future environmental warming may have profound effects on the structure and functioning of aquatic communities and ecosystems.

Warming alters community size structure and ecosystem functioning

by Gabriel Yvon-Durocher

Global warming can affect all levels of biological complexity, though we currently understand least about its... more Global warming can affect all levels of biological complexity, though we currently understand least about its potential impact on communities and ecosystems. At the ecosystem level, warming has the capacity to alter the structure of communities and the rates of key ecosystem processes they mediate. Here we assessed the effects of a 4C rise in temperature on the size structure and taxonomic composition of benthic communities in aquatic mesocosms, and the rates of detrital decomposition they mediated. Warming had no effect on biodiversity, but altered community size structure in two ways. In spring, warmer systems exhibited steeper size spectra driven by declines in total community biomass and the proportion of large organisms. By contrast, in autumn, warmer systems had shallower size spectra driven by elevated total community biomass and a greater proportion of large organisms. Community-level shifts were mirrored by changes in decomposition rates. Temperature-corrected microbial and macrofaunal decomposition rates reflected the shifts in community structure and were strongly correlated with biomass across mesocosms. Our study demonstrates that the 4C rise in temperature expected by the end of the century has the potential to alter the structure and functioning of aquatic ecosystems profoundly, as well as the intimate linkages between these levels of ecological organization.

Across ecosystem comparisons of size structure: methods, approaches and prospects

by Gabriel Yvon-Durocher

Understanding how ecological communities are structured and how this may vary between different types of ecosystems is... more Understanding how ecological communities are structured and how this may vary between different types of ecosystems is a fundamental question in ecology. We develop a general framework for quantifying size-structure within and among different ecosystem types (e.g. terrestrial, freshwater or marine), via the use of a suite of bivariate relationships between organismal size and properties of individuals, populations, assemblages, pair-wise interactions, and network topology. Each of these relationships can be considered a dimension of size-structure, along which real communities lie on a continuous scale. For example, the strength, slope, or elevation of the body mass-versus-abundance or predator size-versus-prey size relationships may vary systematically among ecosystem types. We draw on examples from the literature and suggest new ways to use allometries for comparing among ecosystem types, which we illustrate by applying them to published data. Finally, we discuss how dimensions of size-structure are interconnected and how we could approach this complex hierarchy systematically. We conclude: (1) there are multiple dimensions of size-structure; (2) communities may be size-structured in some of these dimensions, but not necessarily in others; (3) across-system comparisons via rigorous quantitative statistical methods are possible, and (4) insufficient data are currently available to illuminate thoroughly the full extent and nature of differences in size-structure among ecosystem types.

Consistent temperature dependence of respiration across ecosystems contrasting in thermal history

by Gabriel Yvon-Durocher

Ecosystem respiration is a primary component of the carbon cycle and understanding the mechanisms that determine its... more Ecosystem respiration is a primary component of the carbon cycle and understanding the mechanisms that determine its temperature dependence will be important for predicting how rates of carbon efflux might respond to global warming. We used a rare model system, comprising a network of geothermally heated streams ranging in temperature from 5 °C to 25 °C, to explore the nature of the relationship between respiration and temperature. Using this ‘natural experiment’, we tested whether the natal thermal regime of stream communities influenced the temperature dependence of respiration in the absence of other potentially confounding variables. An empirical survey of 13 streams across the thermal gradient revealed that the temperature dependence of whole-stream respiration was equivalent to the average activation energy of the respiratory complex (0.6–0.7 eV). This observation was also consistent for in-situ benthic respiration. Laboratory experiments, incubating biofilms from four streams across the thermal gradient at a range of temperatures, revealed that the activation energy and Q10 of respiration were remarkably consistent across streams, despite marked differences in their thermal history and significant turnover in species composition. Furthermore, absolute rates of respiration at standardised temperature were also unrelated to ambient stream temperature, but strongly reflected differences in biofilm biomass. Together, our results suggest that the core biochemistry,which drives the kinetics of oxidative respiratory metabolism, may be well conserved among diverse taxa and environments, and that the intrinsic sensitivity of respiration to temperature is not influenced by ambient environmental temperature.

Large mammal status in Peninsula Malaysia. 1991

by M.T. Abdullah, PhD

Cave Bats of Sarawak Malaysian Borneo. 2011

by M.T. Abdullah, PhD

New records for bats observed during this study New records for bats observed during this study

Understanding Biodiversity with Socio-Cultural & Environmental Aspects. 30 April 2011

by M.T. Abdullah, PhD

This paper discusses on some concepts and new ideas related to the high biological diversity in Malaysia. This may be... more This paper discusses on some concepts and new ideas related to the high biological diversity in Malaysia. This may be known as integrative biological diversity.

Warming alters community size structure and ecosystem functioning

by Matteo Dossena

RJ Hobbs and KN Suding (Eds.): New models for ecosystems dynamics and restoration

by James Millington

Landscape Ecology 24(9) 1269-1270

Identification of a new type of ecological hazard of chemicals: inhibition of processes of ecological remediation

by Sergei Ostroumov

Environmental Reconstruction in Microsociological Theory for Microsociological Reconstruction in Environmental Sociology

by Brad Brewster

PhD Dissertation. Completed in 2011. University of Wisconsin-Madison. Done under the supervision of Michael Mayerfeld Bell.

I survey a collection of pedagogical resources in environmental sociology, including syllabi, textbooks, readers, and... more I survey a collection of pedagogical resources in environmental sociology, including syllabi, textbooks, readers, and handbooks, to show that what’s being taught and perpetuated as environmental sociology, via field-defining theories, is actually environmental macrosociology, leaving out the micro. I argue that pedagogical and theoretical problems follow from such one-sidedness. To correct for this imbalance, I turn to social psychological philosopher George Herbert Mead and microsociological theorist of everyday life Erving Goffman, reconstructing their theories in environmental terms. I show that, contrary to how Mead is often taught in sociology courses as well as how he is often portrayed in environmental sociology, Mead’s broad intellectual interests extended beyond social psychology to the natural world. In doing so, an “environmental Mead” is developed from his socio-environmental thought for a community psychology in environmental sociology. Then, beginning with a partly critical discussion of his view of animals, I move into discussions of how Mead's anti-dualistic philosophy creatively combined social and natural in various ways when it came to his view of objects, of mind, and of nature. Unlike Mead, Goffman was singularly and narrowly interested in everyday social interaction. The problem, then, was how to modify Goffman to environmental uses without losing the distinctive character of Goffman’s work. I address this by formulating a pragmatic construct for exporting Goffman to domains he himself had never been. Along the lines of this construct, then, an “environmental Goffman” is developed from his frame analysis for an environmental sociology of everyday life. I, then, explore applications of Mead and Goffman to fields in environmental studies or closely related to environmental sociology, namely, exploring Goffman’s dramaturgical, ritual, and interaction analysis in terms of community sociology and Mead’s holistic thought by comparison to ecosystem ecology. As a next logical step from the socially contextual, embedded approaches of the self in the community in Mead’s thought and of the self in the social situation in Goffman’s thought, I move up to the next level of analysis, the small group itself, to bring group dynamics into the environmental and conservation social sciences.

Population-level metrics of trophic structure based on stable isotopes and their application to invasion ecology

by Ian Donohue

Jackson, M.C., Donohue, I., Jackson, A.L., Britton, J.R., Harper, D.M. & Grey, J. (2012) Population-level metrics... more Jackson, M.C., Donohue, I., Jackson, A.L., Britton, J.R., Harper, D.M. & Grey, J. (2012) Population-level metrics of trophic structure based on stable isotopes and their application to invasion ecology. PLOS One 7: e31757.

Biological invasions are a significant driver of human-induced global change and many ecosystems sustain sympatric invaders. Interactions occurring among these invaders have important implications for ecosystem structure and functioning, yet they are poorly understood. Here we apply newly developed metrics derived from stable isotope data to provide quantitative measures of trophic diversity within populations or species. We then use these to test the hypothesis that sympatric invaders belonging to the same functional feeding group occupy a smaller isotopic niche than their allopatric counterparts. Two introduced, globally important, benthic omnivores, Louisiana swamp crayfish (Procambarus clarkii) and carp (Cyprinus carpio), are sympatric in Lake Naivasha, Kenya. We applied our metrics to an 8-year data set encompassing the establishment of carp in the lake. We found a strong asymmetric interaction between the two invasive populations, as indicated by inverse correlations between carp abundance and measures of crayfish trophic diversity. Lack of isotopic niche overlap between carp and crayfish in the majority of years indicated a predominantly indirect interaction. We suggest that carp-induced habitat alteration reduced the diversity of crayfish prey, resulting in a reduction in the dietary niche of crayfish. Stable isotopes provide an integrated signal of diet over space and time, offering an appropriate scale for the study of population niches, but few isotope studies have retained the often insightful information revealed by variability among individuals in isotope values. Our population metrics incorporate such variation, are robust to the vagaries of sample size and are a useful additional tool to reveal subtle dietary interactions among species. Although we have demonstrated their applicability specifically using a detailed temporal dataset of species invasion in a lake, they have a wide array of potential ecological applications.

Importance of consumers on exposed and sheltered rocky shores

by Ian Donohue

O'Connor, N.E., Donohue, I., Crowe, T.P. & Emmerson, M.C. (2011) Importance of consumers on exposed and sheltered... more O'Connor, N.E., Donohue, I., Crowe, T.P. & Emmerson, M.C. (2011) Importance of consumers on exposed and sheltered rocky shores. Marine Ecology Progress Series 443: 65-75

It is often suggested that the relative importance of biotic processes, such as recruit- ment, competition and predation of marine benthic species, varies predictably along a gradient of exposure to wave action. Several established models of community dynamics on rocky shores pre- dict that top-down processes are more important for structuring communities on sheltered than on exposed shores. To test the relative dominance of top-down processes, we first measured the establishment of key benthic species (mussels, barnacles and algae) on 3 sheltered and 3 exposed rocky shores in southwest Ireland over two 6 mo periods. We then manipulated the presence of consumers (e.g. grazing gastropods, crabs, whelks), using caged exclosures, on 2 sheltered and 2 exposed shores to test for an interaction between effects of consumers and shore exposure on the establishment of benthic species. In contrast to predictions, we found that consumers strongly affected establishment of all species regardless of shore exposure. We also found that shore expo- sure was not a reliable predictor for spatial and temporal variation in rates of establishment of sessile benthic species. Our findings provide experimental evidence which demonstrates the importance of consumers in early post-settlement stages of benthic species—essential for the development of benthic−pelagic models.

Temperature-associated population diversity in salmon confers benefits to mobile consumers

by Jonathan Armstrong