To download PDF of paper, click on ‘Links’ underneath citation, then click the URL listed.
2020 |
Rossi, Gabriel J Food, Phenology, and Flow—How Prey Phenology and Streamflow Dynamics Affect the Behavior, Ecology, and Recovery of Pacific Salmon PhD Thesis 2020. BibTeX | Tags: behavior, food webs, mediterranean stream, Oncorhynchus mykiss, phenology @phdthesis{Rossi2020, title = {Food, Phenology, and Flow—How Prey Phenology and Streamflow Dynamics Affect the Behavior, Ecology, and Recovery of Pacific Salmon}, author = {Gabriel J Rossi}, year = {2020}, date = {2020-05-31}, keywords = {behavior, food webs, mediterranean stream, Oncorhynchus mykiss, phenology}, pubstate = {published}, tppubtype = {phdthesis} } |
2013 |
Power, Mary E; Holomuzki, Joseph R; Lowe, Rex L Food webs in Mediterranean rivers Journal Article Hydrobiologia, 719 (1), pp. 119-136, 2013. Abstract | Links | BibTeX | Tags: Algal production, Cross-ecosystem fluxes, Detritus Disturbance, Drought, fate Carbon sources, Floods, Food quality, food webs, hydrology, Insect emergence, interaction strength, Mediterranean rivers, River-to-ocean fluxes, seasonality @article{Power2013, title = {Food webs in Mediterranean rivers}, author = {Mary E. Power and Joseph R. Holomuzki and Rex L. Lowe}, url = {https://angelo.berkeley.edu/wp-content/uploads/Power_2013_Hydrobio.pdf}, doi = {10.1007/s10750-013-1510-0}, year = {2013}, date = {2013-05-28}, journal = {Hydrobiologia}, volume = {719}, number = {1}, pages = {119-136}, abstract = {River food webs are subject to two regimes of longitudinally varying ecological control: productivity and disturbance. Light-limited productivity increases as channels widen downstream. Time windows for growth, however, shrink as discharge increases, substrate particle size decreases, and the frequency of flood-driven bed mobilization increases downstream. Mediterranean rivers are periodically reset by hydrologic events with somewhat predictable timing. Typically, a rainy winter with high river discharge is followed by summer drought with little or no rainfall and slowly declining river flow. The magnitude and timing of winter floods and severity of subsequent summer drought can vary considerably from year to year, however. Episodic scouring floods or prolonged periods of drought are experienced as disturbances, stressors, or opportunities by river biota. The timing, duration, and intensity of these hydrologic controls affect performances of individuals, distribution and abundances of populations, and outcomes and consequences of species interactions. These interactions in turn determine how river food webs will assemble, develop, and reconfigure after disturbance. We discuss how spatial variation in solar radiation and spatial and temporal variations in disturbance affects river food webs under Mediterranean climate seasonality, focusing primarily on long-term observations in the Eel River of northwestern California, USA}, keywords = {Algal production, Cross-ecosystem fluxes, Detritus Disturbance, Drought, fate Carbon sources, Floods, Food quality, food webs, hydrology, Insect emergence, interaction strength, Mediterranean rivers, River-to-ocean fluxes, seasonality}, pubstate = {published}, tppubtype = {article} } River food webs are subject to two regimes of longitudinally varying ecological control: productivity and disturbance. Light-limited productivity increases as channels widen downstream. Time windows for growth, however, shrink as discharge increases, substrate particle size decreases, and the frequency of flood-driven bed mobilization increases downstream. Mediterranean rivers are periodically reset by hydrologic events with somewhat predictable timing. Typically, a rainy winter with high river discharge is followed by summer drought with little or no rainfall and slowly declining river flow. The magnitude and timing of winter floods and severity of subsequent summer drought can vary considerably from year to year, however. Episodic scouring floods or prolonged periods of drought are experienced as disturbances, stressors, or opportunities by river biota. The timing, duration, and intensity of these hydrologic controls affect performances of individuals, distribution and abundances of populations, and outcomes and consequences of species interactions. These interactions in turn determine how river food webs will assemble, develop, and reconfigure after disturbance. We discuss how spatial variation in solar radiation and spatial and temporal variations in disturbance affects river food webs under Mediterranean climate seasonality, focusing primarily on long-term observations in the Eel River of northwestern California, USA |
2010 |
Finlay, Jacques C; Doucett, Richard R; McNeely, Camille Tracing energy flow in stream food webs using stable isotopes of hydrogen Journal Article Freshwater Biology, 55 (5), pp. 941–951, 2010. Abstract | Links | BibTeX | Tags: energy flow, food webs, stable isotopes, subsidies, trophic interactions @article{Finlay2010, title = {Tracing energy flow in stream food webs using stable isotopes of hydrogen}, author = {Jacques C. Finlay and Richard R. Doucett and Camille McNeely}, url = {https://angelo.berkeley.edu/wp-content/uploads/Finlay_2010_FreshBio.pdf}, doi = {10.1111/j.1365-2427.2009.02327.x}, year = {2010}, date = {2010-05-01}, journal = {Freshwater Biology}, volume = {55}, number = {5}, pages = {941–951}, abstract = {1. Use of the natural ratios of carbon and nitrogen stable isotopes as tracers of trophic interactions has some clear advantages over alternative methods for food web analyses, yet is limited to situations where organic materials of interest have adequate isotopic separation between potential sources. This constrains the use of natural abundance stable isotope approaches to a subset of ecosystems with biogeochemical conditions favourable to source separation. 2. Recent studies suggest that stable hydrogen isotopes (δD) could provide a robust tracer to distinguish contributions of aquatic and terrestrial production in food webs, but variation in δD of consumers and their organic food sources are poorly known. To explore the utility of the stable hydrogen isotope approach, we examined variation in δD in stream food webs in a forested catchment where variation in δ13C has been described previously. 3. Although algal δD varied by taxa and, to a small degree, between sites, we found consistent and clear separation (by an average of 67‰) from terrestrial carbon sources. Environmental conditions known to affect algal δ13C, such as water velocity and stream productivity did not greatly influence algal δD, and there was no evidence of seasonal variation. In contrast, algal δ13C was strongly affected by environmental factors both within and across sites, was seasonally variable at all sites, and partially overlapped with terrestrial δ13C in all streams with catchment areas larger than 10 km2. 4. While knowledge of isotopic exchange with water and trophic fractionation of δD for aquatic consumers is limited, consistent source separation in streams suggests that δD may provide a complementary food web tracer to δ13C in aquatic food webs. Lack of significant seasonal or spatial variation in δD is a distinct advantage over δ13C for applications in many aquatic ecosystems.}, keywords = {energy flow, food webs, stable isotopes, subsidies, trophic interactions}, pubstate = {published}, tppubtype = {article} } 1. Use of the natural ratios of carbon and nitrogen stable isotopes as tracers of trophic interactions has some clear advantages over alternative methods for food web analyses, yet is limited to situations where organic materials of interest have adequate isotopic separation between potential sources. This constrains the use of natural abundance stable isotope approaches to a subset of ecosystems with biogeochemical conditions favourable to source separation. 2. Recent studies suggest that stable hydrogen isotopes (δD) could provide a robust tracer to distinguish contributions of aquatic and terrestrial production in food webs, but variation in δD of consumers and their organic food sources are poorly known. To explore the utility of the stable hydrogen isotope approach, we examined variation in δD in stream food webs in a forested catchment where variation in δ13C has been described previously. 3. Although algal δD varied by taxa and, to a small degree, between sites, we found consistent and clear separation (by an average of 67‰) from terrestrial carbon sources. Environmental conditions known to affect algal δ13C, such as water velocity and stream productivity did not greatly influence algal δD, and there was no evidence of seasonal variation. In contrast, algal δ13C was strongly affected by environmental factors both within and across sites, was seasonally variable at all sites, and partially overlapped with terrestrial δ13C in all streams with catchment areas larger than 10 km2. 4. While knowledge of isotopic exchange with water and trophic fractionation of δD for aquatic consumers is limited, consistent source separation in streams suggests that δD may provide a complementary food web tracer to δ13C in aquatic food webs. Lack of significant seasonal or spatial variation in δD is a distinct advantage over δ13C for applications in many aquatic ecosystems. |
2009 |
Finlay, Jacques; Doucett, R; McNeely, Camille Tracing energy flow in stream food webs using stable isotopes of hydrogen Journal Article Freshwater Biology, 55 , pp. 941-951, 2009. Abstract | Links | BibTeX | Tags: energy flow, food webs, stable isotopes, subsidies, trophic interactions @article{Finlay2009, title = {Tracing energy flow in stream food webs using stable isotopes of hydrogen}, author = {Jacques Finlay and R. Doucett and Camille McNeely}, url = {https://angelo.berkeley.edu/wp-content/uploads/Finlay_EnerStreamIsot_FreshwEco2009.pdf}, doi = {10.1111/j.1365-2427.2009.02327.x}, year = {2009}, date = {2009-10-21}, journal = {Freshwater Biology}, volume = {55}, pages = {941-951}, abstract = {1. Use of the natural ratios of carbon and nitrogen stable isotopes as tracers of trophic interactions has some clear advantages over alternative methods for food web analyses, yet is limited to situations where organic materials of interest have adequate isotopic separation between potential sources. This constrains the use of natural abundance stable isotope approaches to a subset of ecosystems with biogeochemical conditions favourable to source separation. 2. Recent studies suggest that stable hydrogen isotopes (δD) could provide a robust tracer to distinguish contributions of aquatic and terrestrial production in food webs, but variation in δD of consumers and their organic food sources are poorly known. To explore the utility of the stable hydrogen isotope approach, we examined variation in δD in stream food webs in a forested catchment where variation in δ13C has been described previously. 3. Although algal δD varied by taxa and, to a small degree, between sites, we found consistent and clear separation (by an average of 67‰) from terrestrial carbon sources. Environmental conditions known to affect algal δ13C, such as water velocity and stream productivity did not greatly influence algal δD, and there was no evidence of seasonal variation. In contrast, algal δ13C was strongly affected by environmental factors both within and across sites, was seasonally variable at all sites, and partially overlapped with terrestrial δ13C in all streams with catchment areas larger than 10 km2. 4. While knowledge of isotopic exchange with water and trophic fractionation of δD for aquatic consumers is limited, consistent source separation in streams suggests that δD may provide a complementary food web tracer to δ13C in aquatic food webs. Lack of significant seasonal or spatial variation in δD is a distinct advantage over δ13C for applications in many aquatic ecosystems.}, keywords = {energy flow, food webs, stable isotopes, subsidies, trophic interactions}, pubstate = {published}, tppubtype = {article} } 1. Use of the natural ratios of carbon and nitrogen stable isotopes as tracers of trophic interactions has some clear advantages over alternative methods for food web analyses, yet is limited to situations where organic materials of interest have adequate isotopic separation between potential sources. This constrains the use of natural abundance stable isotope approaches to a subset of ecosystems with biogeochemical conditions favourable to source separation. 2. Recent studies suggest that stable hydrogen isotopes (δD) could provide a robust tracer to distinguish contributions of aquatic and terrestrial production in food webs, but variation in δD of consumers and their organic food sources are poorly known. To explore the utility of the stable hydrogen isotope approach, we examined variation in δD in stream food webs in a forested catchment where variation in δ13C has been described previously. 3. Although algal δD varied by taxa and, to a small degree, between sites, we found consistent and clear separation (by an average of 67‰) from terrestrial carbon sources. Environmental conditions known to affect algal δ13C, such as water velocity and stream productivity did not greatly influence algal δD, and there was no evidence of seasonal variation. In contrast, algal δ13C was strongly affected by environmental factors both within and across sites, was seasonally variable at all sites, and partially overlapped with terrestrial δ13C in all streams with catchment areas larger than 10 km2. 4. While knowledge of isotopic exchange with water and trophic fractionation of δD for aquatic consumers is limited, consistent source separation in streams suggests that δD may provide a complementary food web tracer to δ13C in aquatic food webs. Lack of significant seasonal or spatial variation in δD is a distinct advantage over δ13C for applications in many aquatic ecosystems. |
2004 |
Power, Mary; Vanni, Michael; Stapp, Paul; Polis, Gary Subsidy Effects on Managed Ecosystems: Implications for Sustainable Harvest, Conservation, and Control Book Chapter Polis, Gary; Power, Mary; Huxel, Gary (Ed.): Chapter 24, pp. 387-409, 2004, ISBN: 9780226673257. Abstract | Links | BibTeX | Tags: food webs, landscape level, subsidy @inbook{Power2004, title = {Subsidy Effects on Managed Ecosystems: Implications for Sustainable Harvest, Conservation, and Control}, author = {Mary Power and Michael Vanni and Paul Stapp and Gary Polis}, editor = {Gary Polis and Mary Power and Gary Huxel}, url = {https://angelo.berkeley.edu/wp-content/uploads/Power_2004_FoodWebLandLev_SubsEffects.pdf}, isbn = {9780226673257}, year = {2004}, date = {2004-02-00}, pages = {387-409}, chapter = {24}, abstract = {Scientists rely on food webs—complex networks that trace the flow of nutrients and energy between species and through ecosystems—to understand the infrastructure of ecological communities. But given the complexities of food webs—think of following the flow of nutrients through the microbes, fungi, roots, worms, ants, and birds that pass over or through a single cubic meter of prairie soil—it's not difficult to see why most experiments on food-web dynamics focus on small, local habitats. Yet as this book convincingly shows, important insights come when scientists expand the temporal and spatial scope of their research to look at the ways energy, organisms, nutrients, and pollutants flow not just at the local level, but across whole landscapes—between and among food webs in a wide variety of habitats. Paying special attention to the fertile boundaries between terrestrial, freshwater, and marine ecosystems, Food Webs at the Landscape Level not only shows what this new methodology means for ecology, conservation, and agriculture but also serves as a fitting tribute to Gary Polis and his major contributions to the field.}, keywords = {food webs, landscape level, subsidy}, pubstate = {published}, tppubtype = {inbook} } Scientists rely on food webs—complex networks that trace the flow of nutrients and energy between species and through ecosystems—to understand the infrastructure of ecological communities. But given the complexities of food webs—think of following the flow of nutrients through the microbes, fungi, roots, worms, ants, and birds that pass over or through a single cubic meter of prairie soil—it's not difficult to see why most experiments on food-web dynamics focus on small, local habitats. Yet as this book convincingly shows, important insights come when scientists expand the temporal and spatial scope of their research to look at the ways energy, organisms, nutrients, and pollutants flow not just at the local level, but across whole landscapes—between and among food webs in a wide variety of habitats. Paying special attention to the fertile boundaries between terrestrial, freshwater, and marine ecosystems, Food Webs at the Landscape Level not only shows what this new methodology means for ecology, conservation, and agriculture but also serves as a fitting tribute to Gary Polis and his major contributions to the field. |
Polis, Gary A; Power, Mary E; Huxel, Gary R Food webs at the landscape level Journal Article Ecology and Society, 10 (1), 2004, ISBN: 0-226-67327-8. Abstract | Links | BibTeX | Tags: food webs, landscape ecology @article{Polis2004, title = {Food webs at the landscape level}, author = {Gary A. Polis and Mary E. Power and Gary R. Huxel}, url = {http://www.ecologyandsociety.org/vol10/iss1/art5/}, isbn = {0-226-67327-8}, year = {2004}, date = {2004-01-01}, journal = {Ecology and Society}, volume = {10}, number = {1}, publisher = {University of Chicago Press}, abstract = {Precisely as stated in the title, Food Webs at the Landscape Level is about the integration of two major fields of ecology: food web ecology and landscape ecology. The chapters by many authors examine all types of ecosystems, with particular emphasis on how processes that occur among trophic groups are linked with processes that occur at the landscape level. Consequently, it is also a book about scale and how ecologists might begin to consider that parts of food webs can often operate at very different scales. For example, some communities depend on basal resources that originate from places that are different from those in which the focal food web is located, e.g., inputs of nutrients to lakes from the watershed or output of insect prey from rivers to land predators. Other food webs experience occasional inputs of individuals from a higher trophic level because these predatory populations operate at a larger spatial scale than do other members of the food web. With this timely book, ecologists are finally starting to address the fact that food webs are not static in space or time and that what we used to ignore as "transient" species may actually be playing very important functional roles. This book emerges from a symposium sponsored by the International Association for Ecology in Florence, Italy, in 1998 on food webs and landscapes. This symposium was led by Gary Polis, who died in a boating accident on a research expedition in 2000. It is a testament to his influence in ecology that his work is still being published today. This is perhaps even more surprising because he came to the discipline mostly from an empirical perspective, not a theoretical one. Because he was such a keen observer of the natural world, Polis was able to reorient the field of food web research away from one in which theory played the dominant role, as it had for several decades, to one in which empirical observations once again led theoretical generalizations. Gary Polis was able to inject food web research with new questions arising from natural history observations and bring it at least one step closer to actual biological functioning. We must thank the co-editors Mary Power and Gary Huxel for ensuring that this worthwhile project was completed. The book is excellently edited, with thorough cross-referencing throughout. As an obvious outgrowth of Polis' research interests, this book provides an excellent summary of current thinking in the study of food webs and subsidies across space and time. Most chapters provide more of a case study viewpoint than strong theoretical generalizations. However, because the editors have collected together authors from all sorts of ecological systems, generalizations do emerge. Perhaps the most obvious of these is that subsidies or allocthonous inputs to food webs are ubiquitous across ecosystems. Readers will find chapters on the functioning of food webs and their subsidies in reservoirs, intertidal rocky shores, arid islands, streams, lakes, forests, old fields, agricultural lands and the tundra. Because most chapters represent reviews of several years of experiments and observations, this book is an excellent resource for graduate students interested in beginning food web studies. In addition to discussions of particular food webs, there are also chapters that review advances in methodology, such as stable isotopes that have allowed ecologists to begin to take a landscape approach to food webs. Another generalization that emerges in the book is that a landscape view of food webs will involve studying not only flows across systems but also the permeability of habitats and controls over flows. There are several interesting chapters that explicitly discuss flows in terrestrial environments. In yet another merging of fields, this area of research combines physics of movement with ecological dynamics. Interspersed with many relatively empirical chapters are several theoretical chapters that begin the work needed to develop a general framework that explains how subsidies alter predictions concerning the functioning and stability of food webs. New theory in this area will help unify population, community, and ecosystem ecology. One aspect of the book that I found especially enlightening was the focus on humans as agents of change for the scales and existence of allocthonous inputs to food webs. Through most of our actions on the planet, humans generally act to alter the flows of resources and species in a way that benefits our own productivity, and for some of us more than others. Agriculture is the most obvious form in which this flow alteration occurs, as is discussed in several chapters that will be of special interest to readers of Ecology and Society. In addition, there are chapters that deal with some of the unwanted consequences of flow alteration by humans, including global change and the movement of exotic species. Food Webs at the Landscape Level will be of interest to food web researchers who realize that it is necessary to take into account the scales and sizes of flows between trophic units and habitats. It represents the first step in searching for generalizations in what, until now, has been mainly a series of separate case studies. The book does this by bringing together empirical observations on many systems and by presenting simple mathematical models that help to determine how our current understanding of food webs will change as we include these processes. I do not hesitate to recommend this book to anyone interested in the current status of food web research; in fact, I would require it. }, keywords = {food webs, landscape ecology}, pubstate = {published}, tppubtype = {article} } Precisely as stated in the title, Food Webs at the Landscape Level is about the integration of two major fields of ecology: food web ecology and landscape ecology. The chapters by many authors examine all types of ecosystems, with particular emphasis on how processes that occur among trophic groups are linked with processes that occur at the landscape level. Consequently, it is also a book about scale and how ecologists might begin to consider that parts of food webs can often operate at very different scales. For example, some communities depend on basal resources that originate from places that are different from those in which the focal food web is located, e.g., inputs of nutrients to lakes from the watershed or output of insect prey from rivers to land predators. Other food webs experience occasional inputs of individuals from a higher trophic level because these predatory populations operate at a larger spatial scale than do other members of the food web. With this timely book, ecologists are finally starting to address the fact that food webs are not static in space or time and that what we used to ignore as "transient" species may actually be playing very important functional roles. This book emerges from a symposium sponsored by the International Association for Ecology in Florence, Italy, in 1998 on food webs and landscapes. This symposium was led by Gary Polis, who died in a boating accident on a research expedition in 2000. It is a testament to his influence in ecology that his work is still being published today. This is perhaps even more surprising because he came to the discipline mostly from an empirical perspective, not a theoretical one. Because he was such a keen observer of the natural world, Polis was able to reorient the field of food web research away from one in which theory played the dominant role, as it had for several decades, to one in which empirical observations once again led theoretical generalizations. Gary Polis was able to inject food web research with new questions arising from natural history observations and bring it at least one step closer to actual biological functioning. We must thank the co-editors Mary Power and Gary Huxel for ensuring that this worthwhile project was completed. The book is excellently edited, with thorough cross-referencing throughout. As an obvious outgrowth of Polis' research interests, this book provides an excellent summary of current thinking in the study of food webs and subsidies across space and time. Most chapters provide more of a case study viewpoint than strong theoretical generalizations. However, because the editors have collected together authors from all sorts of ecological systems, generalizations do emerge. Perhaps the most obvious of these is that subsidies or allocthonous inputs to food webs are ubiquitous across ecosystems. Readers will find chapters on the functioning of food webs and their subsidies in reservoirs, intertidal rocky shores, arid islands, streams, lakes, forests, old fields, agricultural lands and the tundra. Because most chapters represent reviews of several years of experiments and observations, this book is an excellent resource for graduate students interested in beginning food web studies. In addition to discussions of particular food webs, there are also chapters that review advances in methodology, such as stable isotopes that have allowed ecologists to begin to take a landscape approach to food webs. Another generalization that emerges in the book is that a landscape view of food webs will involve studying not only flows across systems but also the permeability of habitats and controls over flows. There are several interesting chapters that explicitly discuss flows in terrestrial environments. In yet another merging of fields, this area of research combines physics of movement with ecological dynamics. Interspersed with many relatively empirical chapters are several theoretical chapters that begin the work needed to develop a general framework that explains how subsidies alter predictions concerning the functioning and stability of food webs. New theory in this area will help unify population, community, and ecosystem ecology. One aspect of the book that I found especially enlightening was the focus on humans as agents of change for the scales and existence of allocthonous inputs to food webs. Through most of our actions on the planet, humans generally act to alter the flows of resources and species in a way that benefits our own productivity, and for some of us more than others. Agriculture is the most obvious form in which this flow alteration occurs, as is discussed in several chapters that will be of special interest to readers of Ecology and Society. In addition, there are chapters that deal with some of the unwanted consequences of flow alteration by humans, including global change and the movement of exotic species. Food Webs at the Landscape Level will be of interest to food web researchers who realize that it is necessary to take into account the scales and sizes of flows between trophic units and habitats. It represents the first step in searching for generalizations in what, until now, has been mainly a series of separate case studies. The book does this by bringing together empirical observations on many systems and by presenting simple mathematical models that help to determine how our current understanding of food webs will change as we include these processes. I do not hesitate to recommend this book to anyone interested in the current status of food web research; in fact, I would require it. |
2002 |
Fausch, Kurt D; Power, Mary E; Murakami, Masashi Linkages between stream and forest food webs: Shigeru Nakano’s legacy for ecology in Japan Journal Article TRENDS in Ecology & Evolution, 17 (9), pp. 429-434, 2002. Abstract | Links | BibTeX | Tags: food webs @article{Fausch2002, title = {Linkages between stream and forest food webs: Shigeru Nakano’s legacy for ecology in Japan}, author = {Kurt D. Fausch and Mary E. Power and Masashi Murakami}, url = {https://angelo.berkeley.edu/wp-content/uploads/Fausch_2002_TREE.pdf}, year = {2002}, date = {2002-07-17}, journal = {TRENDS in Ecology & Evolution}, volume = {17}, number = {9}, pages = {429-434}, abstract = {During the 1990s, ecologists such as Gary Polis catalysed a renaissance in food-web research by focusing on trophic processes occurring among habitats at the landscape scale. Examples include prey transported across ecotones to subsidize predators in adjacent habitats, which, in turn, can have strong indirect effects such as initiating trophic cascades. Recent work in Japan by Shigeru Nakano and his colleagues has set new standards of holism and rigor in foodweb research by demonstrating complementary seasonal shifts in prey fluxes across a stream–forest ecotone that sustain higher densities and diversities of consumers in both habitats than would otherwise be supported in either alone. Although Nakano died in a tragic accident at sea with Polis and three other Japanese and American ecologists in March 2000, his work has left an indelible legacy that gives direction and purpose to further research on the significance of complex interrelationships in food webs across landscape scales.}, keywords = {food webs}, pubstate = {published}, tppubtype = {article} } During the 1990s, ecologists such as Gary Polis catalysed a renaissance in food-web research by focusing on trophic processes occurring among habitats at the landscape scale. Examples include prey transported across ecotones to subsidize predators in adjacent habitats, which, in turn, can have strong indirect effects such as initiating trophic cascades. Recent work in Japan by Shigeru Nakano and his colleagues has set new standards of holism and rigor in foodweb research by demonstrating complementary seasonal shifts in prey fluxes across a stream–forest ecotone that sustain higher densities and diversities of consumers in both habitats than would otherwise be supported in either alone. Although Nakano died in a tragic accident at sea with Polis and three other Japanese and American ecologists in March 2000, his work has left an indelible legacy that gives direction and purpose to further research on the significance of complex interrelationships in food webs across landscape scales. |
Power, Mary E; Dietrich, William E Food webs in river networks Journal Article Ecological Research, 17 (4), pp. 451-471, 2002. Abstract | Links | BibTeX | Tags: food chain length, food webs, landscape heterogeneity, river networks, stream ecosystems @article{Power2002, title = {Food webs in river networks}, author = {Mary E. Power and William E. Dietrich}, url = {https://angelo.berkeley.edu/wp-content/uploads/Power_et_al-2002-Ecological_Research1.pdf}, doi = {10.1046/j.1440-1703.2002.00503.x}, year = {2002}, date = {2002-06-28}, journal = {Ecological Research}, volume = {17}, number = {4}, pages = {451-471}, abstract = {Food webs and river drainages are both hierarchical networks and complex adaptive systems. How does living within the second affect the first? Longitudinal gradients in productivity, disturbance regimes and habitat structure down rivers have long interested ecologists, but their effects on food web structure and dynamics are just beginning to be explored. Even less is known about how network structure per se influences river and riparian food webs and their members. We offer some preliminary observations and hypotheses about these interactions, emphasizing observations on upstream–downstream changes in food web structure and controls, and introducing some ideas and predictions about the unexplored question of food web responses to some of the network properties of river drainages. }, keywords = {food chain length, food webs, landscape heterogeneity, river networks, stream ecosystems}, pubstate = {published}, tppubtype = {article} } Food webs and river drainages are both hierarchical networks and complex adaptive systems. How does living within the second affect the first? Longitudinal gradients in productivity, disturbance regimes and habitat structure down rivers have long interested ecologists, but their effects on food web structure and dynamics are just beginning to be explored. Even less is known about how network structure per se influences river and riparian food webs and their members. We offer some preliminary observations and hypotheses about these interactions, emphasizing observations on upstream–downstream changes in food web structure and controls, and introducing some ideas and predictions about the unexplored question of food web responses to some of the network properties of river drainages. |
2000 |
Power, Mary E; Rainey, W E Food webs and resource sheds: Towards spatially delimiting trophic interactions Book Chapter Hutchings, Michael J; John, Elizabeth A; Stewart, Alan J A (Ed.): Ecological Consequences of Environmental Heterogeneity, Chapter 14, pp. 291-314, Blackwell Scientific, Oxford, UK, 2000, ISBN: 0-632-05713-0. Links | BibTeX | Tags: abiotic factors, ecology, food webs, resource sheds, trophic structure @inbook{Power2000, title = {Food webs and resource sheds: Towards spatially delimiting trophic interactions}, author = {Mary E. Power and W. E. Rainey}, editor = {Michael J. Hutchings and Elizabeth A. John and Alan J. A. Stewart }, url = {https://angelo.berkeley.edu/wp-content/uploads/Power_2000_ResShade.pdf}, isbn = {0-632-05713-0}, year = {2000}, date = {2000-00-00}, booktitle = {Ecological Consequences of Environmental Heterogeneity}, pages = {291-314}, publisher = {Blackwell Scientific, Oxford, UK}, chapter = {14}, keywords = {abiotic factors, ecology, food webs, resource sheds, trophic structure}, pubstate = {published}, tppubtype = {inbook} } |
1999 |
Finlay, Jacques C; Power, Mary E; Cabana, Gilbert Effects of water velocity on algal carbon isotope ratios: Implications for river food web studies Journal Article Limnology and Oceanography, 44 , pp. 1198-1203, 1999. Abstract | Links | BibTeX | Tags: carbon isotopes, food webs, water velocity @article{Finlay1999, title = {Effects of water velocity on algal carbon isotope ratios: Implications for river food web studies}, author = {Jacques C. Finlay and Mary E. Power and Gilbert Cabana}, url = {https://angelo.berkeley.edu/wp-content/uploads/Finlay_LimnolOceanogr1999.pdf}, doi = {10.4319/lo.1999.44.5.1198}, year = {1999}, date = {1999-07-13}, journal = {Limnology and Oceanography}, volume = {44}, pages = {1198-1203}, abstract = {We used variation in algal d13C between river habitats to study the spatial scale of energy flow through river food webs. We found a strong negative relationship between herbivore d13C (which reflects algal d13C) and water velocity in three productive Northern California rivers but not in unproductive streams. The contrast among habitats suggests that water velocity affects algal d13C most strongly when CO2 availability is low relative to photosynthetic rates. Our results help explain the wide variation in published river biota d13C and show that past studies using carbon isotope analyses may have significantly underestimated the importance of algal-derived carbon to river food webs. While flow related variation in d13C complicates this common application of carbon isotope analysis, we show that it provides a natural tracer of the flux of algal production derived from different habitats within rivers to higher trophic levels. Measurements of consumer d13C showed that most invertebrate and vertebrate consumers relied on local production, except for filter feeding insects and steelhead trout, which relied on production derived from multiple sources. Stable carbon isotopes may thus be used to spatially delineate the habitats that support river food webs, providing previously unavailable information for understanding and managing river ecosystems.}, keywords = {carbon isotopes, food webs, water velocity}, pubstate = {published}, tppubtype = {article} } We used variation in algal d13C between river habitats to study the spatial scale of energy flow through river food webs. We found a strong negative relationship between herbivore d13C (which reflects algal d13C) and water velocity in three productive Northern California rivers but not in unproductive streams. The contrast among habitats suggests that water velocity affects algal d13C most strongly when CO2 availability is low relative to photosynthetic rates. Our results help explain the wide variation in published river biota d13C and show that past studies using carbon isotope analyses may have significantly underestimated the importance of algal-derived carbon to river food webs. While flow related variation in d13C complicates this common application of carbon isotope analysis, we show that it provides a natural tracer of the flux of algal production derived from different habitats within rivers to higher trophic levels. Measurements of consumer d13C showed that most invertebrate and vertebrate consumers relied on local production, except for filter feeding insects and steelhead trout, which relied on production derived from multiple sources. Stable carbon isotopes may thus be used to spatially delineate the habitats that support river food webs, providing previously unavailable information for understanding and managing river ecosystems. |
1997 |
Power, Mary E; Kupferberg, Sarah J; Minshall, Wayne G; Molles, Manuel C; Parker, Michael S Sustaining Western Aquatic Food Webs Technical Report Aquatic Ecosystems Symposium, Tempe AZ. Report to the Western Water Policy Review, a Presidential Advisory Commission. Arizona State University, Tempe, Arizona, Report to the Western Water Policy Review Advisory Commission, 1997. Links | BibTeX | Tags: aquatic ecosystems, ecological services, food webs @techreport{Power1997, title = {Sustaining Western Aquatic Food Webs}, author = {Mary E. Power and Sarah J. Kupferberg and G. Wayne Minshall and Manuel C. Molles and Michael S. Parker}, editor = {Wendell L. Minckley}, url = {https://repository.unm.edu/bitstream/handle/1928/2784/AQUA%20Pt.1.pdf?sequence=4}, year = {1997}, date = {1997-09-00}, address = {Arizona State University, Tempe, Arizona}, institution = {Aquatic Ecosystems Symposium, Tempe AZ. Report to the Western Water Policy Review, a Presidential Advisory Commission.}, type = {Report to the Western Water Policy Review Advisory Commission}, keywords = {aquatic ecosystems, ecological services, food webs}, pubstate = {published}, tppubtype = {techreport} } |
Kupferberg, Sarah J Facilitation of periphyton production by tadpole grazing: functional differences between species Journal Article Freshwater Biology, 37 (2), pp. 427-439, 1997. Abstract | Links | BibTeX | Tags: AQUATIC INSECTS, bottom-up, competition, epiphytes, food webs, herbivores, nutrient, stream periphyton, top-down, trophic cascades @article{Kupferberg1997c, title = {Facilitation of periphyton production by tadpole grazing: functional differences between species}, author = {Sarah J. Kupferberg}, url = {https://angelo.berkeley.edu/wp-content/uploads/KUPFERBERG_Freshwater_Biology1997.pdf}, year = {1997}, date = {1997-04-00}, journal = {Freshwater Biology}, volume = {37}, number = {2}, pages = {427-439}, abstract = {1. This study examined how interactions between resources that vary in edibility, and herbivores that vary in ability to acquire resources, control primary productivity. In a northern California river, grazing on Cladophora glomerata, a relatively inedible filamentous green alga, and its more nutritious epiphytic diatoms, was manipulated by exposing cobbles to tadpoles (Rana boylii or Hyla regilla) or excluding tadpoles. 2. Rana indirectly facilitated Cladophora by removing diatoms, whereas Hyla did not significantly change biomass relative to controls. Algal ash-free dry mass on cobbles in Rana treatments was 65 and 72% greater than on controls in two years of investigation (1991 and 1993). Rana decreased epiphytic diatom biovolume by 56% and detritus by 87%. 3. Because nitrogen excretion rates of Hyla and Rana were similar, the differences in effect between the two species were probably due to their roles as consumers rather than as recyclers. 4. The net effect of Rana on periphyton was a 10% increase in areal specific primary productivity (mg O-2 h(-1) m(-2)); Hyla caused an 18% decrease. Rana decreased biomass-specific productivity (mg O-2 h(-1) g(-1)) 44%; Hyla had no effect. 5. In tadpole exclosures, grazers such as baetid mayfly larvae (mostly Centroptilum sp.) were 4.7 (1991) and 1.8 (1993) times more abundant, and midge larvae (Chironomidae) were 2.5 (1991) and 2 (1993) times more abundant than in Rana enclosures. Invertebrate assemblages in Hyla enclosures, however, were similar to exclosures. Few predatory insects and fish colonized Rana enclosures. Path analyses indicated that Rana affected macroinvertebrates via both interference and exploitation of epiphytic diatoms.}, keywords = {AQUATIC INSECTS, bottom-up, competition, epiphytes, food webs, herbivores, nutrient, stream periphyton, top-down, trophic cascades}, pubstate = {published}, tppubtype = {article} } 1. This study examined how interactions between resources that vary in edibility, and herbivores that vary in ability to acquire resources, control primary productivity. In a northern California river, grazing on Cladophora glomerata, a relatively inedible filamentous green alga, and its more nutritious epiphytic diatoms, was manipulated by exposing cobbles to tadpoles (Rana boylii or Hyla regilla) or excluding tadpoles. 2. Rana indirectly facilitated Cladophora by removing diatoms, whereas Hyla did not significantly change biomass relative to controls. Algal ash-free dry mass on cobbles in Rana treatments was 65 and 72% greater than on controls in two years of investigation (1991 and 1993). Rana decreased epiphytic diatom biovolume by 56% and detritus by 87%. 3. Because nitrogen excretion rates of Hyla and Rana were similar, the differences in effect between the two species were probably due to their roles as consumers rather than as recyclers. 4. The net effect of Rana on periphyton was a 10% increase in areal specific primary productivity (mg O-2 h(-1) m(-2)); Hyla caused an 18% decrease. Rana decreased biomass-specific productivity (mg O-2 h(-1) g(-1)) 44%; Hyla had no effect. 5. In tadpole exclosures, grazers such as baetid mayfly larvae (mostly Centroptilum sp.) were 4.7 (1991) and 1.8 (1993) times more abundant, and midge larvae (Chironomidae) were 2.5 (1991) and 2 (1993) times more abundant than in Rana enclosures. Invertebrate assemblages in Hyla enclosures, however, were similar to exclosures. Few predatory insects and fish colonized Rana enclosures. Path analyses indicated that Rana affected macroinvertebrates via both interference and exploitation of epiphytic diatoms. |
1996 |
Power, Mary E; Dietrich, WIlliam E; Finlay, Jacques C Dams and downstream aquatic biodiversity: Potential food web consequences of hydrologic and geomorphic change Journal Article Environmental Management, 20 (6), pp. 887-895, 1996, ISSN: 0364-152X. Abstract | Links | BibTeX | Tags: dams, food webs, hydrologic disturbance, predator-prey dynamics, succession @article{Power1996, title = {Dams and downstream aquatic biodiversity: Potential food web consequences of hydrologic and geomorphic change}, author = {Mary E. Power and WIlliam E. Dietrich and Jacques C. Finlay}, url = {https://angelo.berkeley.edu/wp-content/uploads/Power_EnvironmentalManagment1996.pdf}, doi = {10.1007/BF01205969}, issn = {0364-152X}, year = {1996}, date = {1996-11-00}, journal = {Environmental Management}, volume = {20}, number = {6}, pages = {887-895}, abstract = {Responses of rivers and river ecosystems to dams are complex and varied, as they depend on local sediment supplies, geomorphic constraints, climate, dam structure and operation, and key attributes of the biota. Therefore, ''one-size-fits-all'' prescriptions cannot substitute for local knowledge in developing prescriptions for dam structure and operation to protect local biodiversity. One general principle is self-evident: that biodiversity is best protected in rivers where physical regimes are the most natural. A sufficiently natural regime of flow variation is particularly crucial for river biota and food webs. We review our research and that of others to illustrate the ecological importance or alternating periods of low and high flow, of periodic bed scour, and of floodplain inundation and dewatering. These fluctuations regulate both the life cycles of river biota and species interactions in the food webs that sustain them. Even if the focus of biodiversity conservation efforts is on a target species rather than whole ecosystems, a food web perspective is necessary, because populations of any species depend critically on how their resources, prey, and potential predators also respond to environmental change. In regulated rivers, managers must determine how the frequency, magnitude, and timing of hydrologic events interact to constrain or support species and food webs. Simple ecological modeling, tailored to local systems, may provide a framework and some insight into explaining ecosystem response to dams and should give direction to mitigation efforts. }, keywords = {dams, food webs, hydrologic disturbance, predator-prey dynamics, succession}, pubstate = {published}, tppubtype = {article} } Responses of rivers and river ecosystems to dams are complex and varied, as they depend on local sediment supplies, geomorphic constraints, climate, dam structure and operation, and key attributes of the biota. Therefore, ''one-size-fits-all'' prescriptions cannot substitute for local knowledge in developing prescriptions for dam structure and operation to protect local biodiversity. One general principle is self-evident: that biodiversity is best protected in rivers where physical regimes are the most natural. A sufficiently natural regime of flow variation is particularly crucial for river biota and food webs. We review our research and that of others to illustrate the ecological importance or alternating periods of low and high flow, of periodic bed scour, and of floodplain inundation and dewatering. These fluctuations regulate both the life cycles of river biota and species interactions in the food webs that sustain them. Even if the focus of biodiversity conservation efforts is on a target species rather than whole ecosystems, a food web perspective is necessary, because populations of any species depend critically on how their resources, prey, and potential predators also respond to environmental change. In regulated rivers, managers must determine how the frequency, magnitude, and timing of hydrologic events interact to constrain or support species and food webs. Simple ecological modeling, tailored to local systems, may provide a framework and some insight into explaining ecosystem response to dams and should give direction to mitigation efforts. |
J.T. Wootton, Parker M S; Power, M E The effect of disturbance on river food webs Journal Article Science, 273 (5281), pp. 1558-1560, 1996. Abstract | Links | BibTeX | Tags: disturbance, food webs @article{Wootton1996, title = {The effect of disturbance on river food webs}, author = {J.T. Wootton, M.S. Parker and M.E. Power}, url = {https://angelo.berkeley.edu/wp-content/uploads/Wootton_1996_Science.pdf}, year = {1996}, date = {1996-00-00}, journal = {Science}, volume = {273}, number = {5281}, pages = {1558-1560}, abstract = {A multitrophic model integrating the effects of flooding disturbance and food web interactions in rivers predicted that removing floods would cause increases of predator-resistant grazing insects, which would divert energy away from the food chain leading to predatory fish. Experimental manipulations of predator-resistant grazers and top predators, and large-scale comparisons of regulated and unregulated rivers, verified the model predictions. Thus, multitrophic models can successfully synthesize a variety of ecological processes, and conservation programs may benefit by taking a food web perspective instead of concentrating on a single species.}, keywords = {disturbance, food webs}, pubstate = {published}, tppubtype = {article} } A multitrophic model integrating the effects of flooding disturbance and food web interactions in rivers predicted that removing floods would cause increases of predator-resistant grazing insects, which would divert energy away from the food chain leading to predatory fish. Experimental manipulations of predator-resistant grazers and top predators, and large-scale comparisons of regulated and unregulated rivers, verified the model predictions. Thus, multitrophic models can successfully synthesize a variety of ecological processes, and conservation programs may benefit by taking a food web perspective instead of concentrating on a single species. |
1995 |
Power, Mary E; Sun, Adrian; Parker, Gary; Dietrich, William E; Wootton, Timothy J Hydraulic food chain models Journal Article BioScience, 45 (3), pp. 159-167, 1995, (See stable URL attached; file size exceeds maximum allowable for Angelo.). Links | BibTeX | Tags: consequences, dynamics, ecosystems, food webs, hetergeneity, patterns, productivity, Southern Ontario, STREAM, top-down @article{Power1995b, title = {Hydraulic food chain models}, author = {Mary E. Power and Adrian Sun and Gary Parker and William E. Dietrich and J. Timothy Wootton}, url = {http://www.jstor.org/stable/1312555}, doi = {10.2307/1312555}, year = {1995}, date = {1995-03-00}, journal = {BioScience}, volume = {45}, number = {3}, pages = {159-167}, note = {See stable URL attached; file size exceeds maximum allowable for Angelo.}, keywords = {consequences, dynamics, ecosystems, food webs, hetergeneity, patterns, productivity, Southern Ontario, STREAM, top-down}, pubstate = {published}, tppubtype = {article} } |
1992 |
Power, M E; Marks, J C; Parker, Michael S Variation in the vulnerability of prey to different predators: Community-level consequences Journal Article Ecology, 73 (6), pp. 2218-2223, 1992. Abstract | Links | BibTeX | Tags: anti-predator defenses, attached algae, chironomidae, Cladophora, fish, food webs, omnivory, predatory invertebrates, river communities, strong interactors, trophic cascades @article{Power1992, title = {Variation in the vulnerability of prey to different predators: Community-level consequences}, author = {M.E. Power and J.C. Marks and Michael S. Parker}, url = {https://angelo.berkeley.edu/wp-content/uploads/Power_1992_Eco3.pdf}, doi = {10.2307/1941469}, year = {1992}, date = {1992-12-00}, journal = {Ecology}, volume = {73}, number = {6}, pages = {2218-2223}, abstract = { Midge larvae (Diptera, Chironomidae) that weave filamentous algae into retreats or tufts, are dominant primary consumers in a river food web. In a previous study, densities of tuft-weaving midges increased in the presence of large fish. In the absence of large fish, midges decreased as densities of predatory invertebrates built up, and higher standing crops of algae were maintained. To examine the mechanisms underlying these dynamics, we compared the vulnerability of tuft-weaving midges (naked or in algal tufts) to fish and predatory invertebrates, in field and laboratory experiments. When midges were exposed for 1 h in the river to fish, 15 out of 15 midges in tufts survived, while 15 of 15 naked midges were consumed. Tufts afforded only partial protection to midges exposed to invertebrate predators, however. After 1 h, enhancement of survivorship by tufts was moderately significant for midges exposed to aeshnids, and insignificant for midges exposed to lestids and naucorids. We suggest that the vulnerability of tuft-weaving midges to invertebrate predators, and their relative invulnerability to fish, sets the stage for trophic cascades observed in this system. Fish, by consuming small predators, release midges, which graze down algae. The strong effects of fish as fourth-level consumers would not be predicted from their diets, in which algivorous mayflies dominate (>60% of the insect biomass found in each of the two most common fish species). Nevertheless, fish in this food web act as fourth-level, rather than third-level, consumers because of the differential vulnerability of one guild of primary consumers, which, when released from predation, can suppress plants.}, keywords = {anti-predator defenses, attached algae, chironomidae, Cladophora, fish, food webs, omnivory, predatory invertebrates, river communities, strong interactors, trophic cascades}, pubstate = {published}, tppubtype = {article} } Midge larvae (Diptera, Chironomidae) that weave filamentous algae into retreats or tufts, are dominant primary consumers in a river food web. In a previous study, densities of tuft-weaving midges increased in the presence of large fish. In the absence of large fish, midges decreased as densities of predatory invertebrates built up, and higher standing crops of algae were maintained. To examine the mechanisms underlying these dynamics, we compared the vulnerability of tuft-weaving midges (naked or in algal tufts) to fish and predatory invertebrates, in field and laboratory experiments. When midges were exposed for 1 h in the river to fish, 15 out of 15 midges in tufts survived, while 15 of 15 naked midges were consumed. Tufts afforded only partial protection to midges exposed to invertebrate predators, however. After 1 h, enhancement of survivorship by tufts was moderately significant for midges exposed to aeshnids, and insignificant for midges exposed to lestids and naucorids. We suggest that the vulnerability of tuft-weaving midges to invertebrate predators, and their relative invulnerability to fish, sets the stage for trophic cascades observed in this system. Fish, by consuming small predators, release midges, which graze down algae. The strong effects of fish as fourth-level consumers would not be predicted from their diets, in which algivorous mayflies dominate (>60% of the insect biomass found in each of the two most common fish species). Nevertheless, fish in this food web act as fourth-level, rather than third-level, consumers because of the differential vulnerability of one guild of primary consumers, which, when released from predation, can suppress plants. |