Academic literature on the topic 'Fourth trophic level'
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Journal articles on the topic "Fourth trophic level"
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Nair, Abhilash, Toby Fountain, Suvi Ikonen, Sami P. Ojanen, and Saskya van Nouhuys. "Spatial and temporal genetic structure at the fourth trophic level in a fragmented landscape." Proceedings of the Royal Society B: Biological Sciences 283, no. 1831 (May 25, 2016): 20160668. http://dx.doi.org/10.1098/rspb.2016.0668.
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A fragmented habitat becomes increasingly fragmented for species at higher trophic levels, such as parasitoids. To persist, these species are expected to possess life-history traits, such as high dispersal, that facilitate their ability to use resources that become scarce in fragmented landscapes. If a specialized parasitoid disperses widely to take advantage of a sparse host, then the parasitoid population should have lower genetic structure than the host. We investigated the temporal and spatial genetic structure of a hyperparasitoid (fourth trophic level) in a fragmented landscape over 50 × 70 km, using microsatellite markers, and compared it with the known structures of its host parasitoid, and the butterfly host which lives as a classic metapopulation. We found that population genetic structure decreases with increasing trophic level. The hyperparasitoid has fewer genetic clusters ( K = 4), than its host parasitoid ( K = 15), which in turn is less structured than the host butterfly ( K = 27). The genetic structure of the hyperparasitoid also shows temporal variation, with genetic differentiation increasing due to reduction of the population size, which reduces the effective population size. Overall, our study confirms the idea that specialized species must be dispersive to use a fragmented host resource, but that this adaptation has limits.
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Rand, Tatyana A., F. J. Frank van Veen, and Teja Tscharntke. "Landscape complexity differentially benefits generalized fourth, over specialized third, trophic level natural enemies." Ecography 35, no. 2 (February 2012): 97–104. http://dx.doi.org/10.1111/j.1600-0587.2011.07016.x.
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Araj, Salah-Eddin, Steve Wratten, Alison Lister, and Hannah Buckley. "Adding floral nectar resources to improve biological control: Potential pitfalls of the fourth trophic level." Basic and Applied Ecology 10, no. 6 (September 2009): 554–62. http://dx.doi.org/10.1016/j.baae.2008.12.001.
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Buitenhuis, R., L. E. M. Vet, G. Boivin, and J. Brodeur. "Foraging behaviour at the fourth trophic level: a comparative study of host location in aphid hyperparasitoids." Entomologia Experimentalis et Applicata 114, no. 2 (February 2005): 107–17. http://dx.doi.org/10.1111/j.1570-7458.2005.00234.x.
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Chen, Cong, Rieta Gols, Arjen Biere, and Jeffrey A. Harvey. "Differential effects of climate warming on reproduction and functional responses on insects in the fourth trophic level." Functional Ecology 33, no. 4 (January 28, 2019): 693–702. http://dx.doi.org/10.1111/1365-2435.13277.
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Nahrung, Helen F., and Michael P. Duffy. "Exploring the fourth trophic level: do hyperparasitoids infl uence biocontrol of a forestry pest in a native system?" New Zealand Entomologist 31, no. 1 (February 2008): 59–66. http://dx.doi.org/10.1080/00779962.2008.9722167.
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Gorbatenko, K. M., and I. V. Melnikov. "TROPHODYNAMICS OF MARINE ORGANISMS IN THE EPIPELAGIC LAYER OF THE OKHOTSK SEA IN 2000S." Izvestiya TINRO 198 (October 2, 2019): 143–63. http://dx.doi.org/10.26428/1606-9919-2019-198-143-163.
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New data on matter and energy transfer between major components of the Okhotsk Sea ecosystem are obtained on the base of trophodynamic modeling, taking into consideration their production and food consumption rates. The main trophodynamic relationships in the pelagic and bottom communities are determined from observations on zooplankton and nekton abundance, organic carbon content, food habits of marine organisms, and their isotope composition in 2000–2014. The total zooplankton production in the entire Okhotsk Sea in these years is assessed as 2616 . 106 t in raw weight, including 2275 . 106 t for non-predatory plankton, and 341 . 106 t for predatory plankton. So high total production of zooplankton is conditioned by favorable environmental conditions and dominance of high-productive species. Taking into account the rate of zooplankton consumption by predators, only 22.4 % of the total annual zooplankton production was consumed annually, with 16.2 % grazed by predatory plankton and 6.2 % by nekton. In carbon units, 831.0 . 106 tC was produced annually in the Okhotsk Sea at the first trophic level, 177.4 . 106 tC at the second trophic level, 18.1 . 106 tC at the third trophic level, 0.74 . 106 tC at the fourth trophic level, and 0.016 . 106 tC at the fifth trophic level. Pelagic nekton consumed 159 . 106 tC annually. The nekton prey included 85.5 % of zooplankton, 12.8 % of nekton, and 1.7 % of zoobenthos, by biomass. The main part of zooplankton consumed by nekton (50.7 %) was grazed by walleye pollock, 18.9 % by herring, 16.6 % by squids, 7.6 % by capelin, 5.3 % by deep-sea smelt, and 0.9 % by salmons. The total annual production of organisms in the epipelagic layer of the Okhotsk Sea exceeded 109 tons of C (1027.4 . 106 tC/year equal to the biomass of 17.85 . 109 t in wet weight). Primary production is estimated as 67.60 % of gross production in carbon units, microheterotrophic organisms produce 13.30 %, dominant zooplankton groups — 18.60 % (copepods 11.40 %, euphausiids 5.50 %, sagittas 1.20 %, and hyperiids 0.50 %), the portion of nekton production is estimated as 0.13 % of gross production.
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Jonsson, M., S. D. Wratten, K. A. Robinson, and S. A. Sam. "The impact of floral resources and omnivory on a four trophic level food web." Bulletin of Entomological Research 99, no. 3 (December 9, 2008): 275–85. http://dx.doi.org/10.1017/s0007485308006275.
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AbstractOmnivory is common among arthropods, but little is known about how availability of plant resources and prey affects interactions between species operating at the third and fourth trophic level. We used laboratory and field cage experiments to investigate how the provision of flowers affects an omnivorous lacewing, Micromus tasmaniae (Hemerobiidae) and its parasitoid Anacharis zealandica (Figitidae). The adult lacewing is a true omnivore that feeds on both floral resources and aphids, whereas the parasitoid is a life-history omnivore, feeding on lacewing larvae in the larval stage and floral nectar as an adult. We showed that the effect of floral resources (buckwheat) on lacewing oviposition depends on prey (aphid) density, having a positive effect only at low prey density and that buckwheat substantially increases the longevity of the adult parasitoid. In field cages, we tested how provision of flowering buckwheat affects the dynamics of a four trophic level system, comprising parasitoids, lacewings, pea aphids and alfalfa. We found that provision of buckwheat decreased the density of lacewings in the first phase of the experiment when the density of aphids was high. This effect was probably caused by increased rate of parasitism by the parasitoid, which benefits from the presence of buckwheat. Towards the end of the experiment when the aphid populations had declined to low levels, the effect of buckwheat on lacewing density became positive, probably because lacewings were starving in the no-buckwheat treatment. Although presence of buckwheat flowers did not affect aphid populations in the field cages, these findings highlight the need to consider multitrophic interactions when proposing provision of floral resources as a technique for sustainable pest management.
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Schulz, Ashley N., Rima D. Lucardi, and Travis D. Marsico. "Successful Invasions and Failed Biocontrol: The Role of Antagonistic Species Interactions." BioScience 69, no. 9 (August 7, 2019): 711–24. http://dx.doi.org/10.1093/biosci/biz075.
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Abstract Understanding the successes and failures of nonnative species remains challenging. In recent decades, researchers have developed the enemy release hypothesis and other antagonist hypotheses, which posit that nonnative species either fail or succeed in a novel range because of the presence or absence of antagonists. The premise of classical biological control of invasive species is that top-down control works. We identify twelve existing hypotheses that address the roles that antagonists from many trophic levels play during plant and insect invasions in natural environments. We outline a unifying framework of antagonist hypotheses to simplify the relatedness among the hypotheses, incorporate the role of top-down and bottom-up influences on nonnative species, and encourage expansion of experimental assessments of antagonist hypotheses to include belowground and fourth trophic level antagonists. A mechanistic understanding of antagonists and their impacts on nonnative species is critical in a changing world.
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Härri, Simone A., Jochen Krauss, and Christine B. Müller. "Fungal endosymbionts of plants reduce lifespan of an aphid secondary parasitoid and influence host selection." Proceedings of the Royal Society B: Biological Sciences 275, no. 1651 (August 5, 2008): 2627–32. http://dx.doi.org/10.1098/rspb.2008.0594.
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Complex biotic interactions shape ecological communities of plants, herbivores and their natural enemies. In studies of multi-trophic interactions, the presence of small, invisible micro-organisms associated with plants and those of a fourth above-ground trophic level have often been neglected. Incorporating these neglected factors improves our understanding of the processes within a multi-trophic network. Here, we ask whether the presence of a fungal endosymbiont, which alters plant quality by producing herbivore-toxic substances, trickles up the food chain and affects the performance and host-selection behaviour of aphid secondary parasitoids. We simultaneously offered hosts from endophyte-free and endophyte-infected environments to secondary parasitoids. Older and more experienced parasitoid females discriminated against hosts from the endophyte-infected environment. Developing in lower quality hosts from the endophyte-infected environment reduced the lifespan of secondary parasitoids. This indicates that aphid secondary parasitoids can perceive the disadvantage for their developing offspring in parasitoids from the endophyte environment and can learn to discriminate against them. In the field, this discrimination ability may shift the success of primary parasitoids to endophyte-infected plants, which co-occur with endophyte-free plants. Ultimately, the control of aphids depends on complex interactions between primary and secondary parasitoids and their relative sensitivity to endophytic fungi.
Dissertations / Theses on the topic "Fourth trophic level"
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Robinson, K. A. "Use of floral resources by the lacewing Micromus tasmaniae and its parasitoid Anacharis zealandica, and the consequences for biological control by M. tasmaniae." Diss., Lincoln University, 2009. http://hdl.handle.net/10182/823.
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Arthropod species that have the potential to damage crops are food resources for communities of predators and parasitoids. From an agronomic perspective these species are pests and biocontrol agents respectively, and the relationships between them can be important determinants of crop yield and quality. The impact of biocontrol agents on pest populations may depend on the availability of other food resources in the agroecosystem. A scarcity of such resources may limit biological control and altering agroecosystem management to alleviate this limitation could contribute to pest management. This is a tactic of ‘conservation biological control’ and includes the provision of flowers for species that consume prey as larvae but require floral resources in their adult stage. The use of flowers for pest management requires an understanding of the interactions between the flowers, pests, biocontrol agents and non-target species. Without this, attempts to enhance biological control might be ineffective or detrimental. This thesis develops our understanding in two areas which have received relatively little attention: the role of flowers in biological control by true omnivores, and the implications of flower use by fourth-trophic-level life-history omnivores. The species studied were the lacewing Micromus tasmaniae and its parasitoid Anacharis zealandica. Buckwheat flowers Fagopyrum esculentum provided floral resources and aphids Acyrthosiphon pisum served as prey. Laboratory experiments with M. tasmaniae demonstrated that although prey were required for reproduction, providing flowers increased survival and oviposition when prey abundance was low. Flowers also decreased prey consumption by the adult lacewings. These experiments therefore revealed the potential for flowers to either enhance or disrupt biological control by M. tasmaniae. Adult M. tasmaniae were collected from a crop containing a strip of flowers. Analyses to determine the presence of prey and pollen in their digestive tracts suggested that predation was more frequent than foraging in flowers. It was concluded that the flower strip probably did not affect biological control by lacewings in that field, but flowers could be significant in other situations. The lifetime fecundity of A. zealandica was greatly increased by the presence of flowers in the laboratory. Providing flowers therefore has the potential to increase parasitism of M. tasmaniae and so disrupt biological control. A. zealandica was also studied in a crop containing a flower strip. Rubidium-marking was used to investigate nectar-feeding and dispersal from the flowers. In addition, the parasitoids’ sugar compositions were determined by HPLC and used to infer feeding histories. Although further work is required to develop the use of these techniques in this system, the results suggested that A. zealandica did not exploit the flower strip. The sugar profiles suggested that honeydew had been consumed by many of the parasitoids. A simulation model was developed to explore the dynamics of aphid, lacewing and parasitoid populations with and without flowers. This suggested that if M. tasmaniae and A. zealandica responded to flowers as in the laboratory, flowers would only have a small effect on biological control within a single period of a lucerne cutting cycle. When parasitoids were present, the direct beneficial effect of flowers on the lacewing population was outweighed by increased parasitism, reducing the potential for biological control in future crops. The results presented in this thesis exemplify the complex interactions that may occur as a consequence of providing floral resources in agroecosystems and re-affirm the need for agroecology to inform the development of sustainable pest management techniques.
Book chapters on the topic "Fourth trophic level"
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Beddington, John R., and Geoffrey P. Kirkwood. "Fisheries." In Theoretical Ecology. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780199209989.003.0014.
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The depletion of fish stocks on a global scale is well documented. The United Nations Food and Agriculture Organisation collects statistics on fisheries from all states and, despite obvious shortcomings in the data, a clear picture has been available for some time. Garcia and Grainger (2005) have succinctly documented the position from the latest available date: in 2003, only 3% of stocks were underexploited and 26% moderately exploited, while 52% were fully exploited, 16% were overfished, 7% were depleted, and 1% were recovering from earlier depletion. These global statistics mask two important phenomena. The first, highlighted by Pauly et al. (1998), is that fisheries are increasingly focusing on species lower down in the food-web and the second, highlighted by Myers and Worm (2003, 2005), is that large predatory fish have been particularly reduced in abundance. Both of these analyses are somewhat flawed. In the case of Pauly et al. there are two problems: the first is that the metrics used for the mean trophic level are presented as simple numbers with no estimates of error or indeed sensitivity. In such a situation, the changes in mean trophic levels are hard to interpret, particularly where the mean trophic level changes by at most around 10% over four decades. The second problem has been highlighted by a recent paper by Essington et al. (2006). They point out that in the periods when according to the analysis of Pauly et al. the mean trophic level was declining, in most cases catches of apex predators and indeed all upper trophic levels increased (an exception is the North Atlantic). In the case of the Myers and Worm analysis, they used the catch per unit of effort (CPUE) as an index of abundance. As discussed later in this chapter, there are problems with this, but more importantly for some key apex predators, in particular large tunas, the CPUE declines in the early stages of the fishery, where catches are small, but remains relatively stable under a regime of much higher catches. In such a situation, the interpretation that the CPUE reflects changes in abundance is clearly problematic.
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"Challenges for Diadromous Fishes in a Dynamic Global Environment." In Challenges for Diadromous Fishes in a Dynamic Global Environment, edited by R. Niloshini Sinatamby, J. Brian Dempson, Gerald Chaput, Francois Caron, Eero Niemelä, Jaakko Erkinaro, and Michael Power. American Fisheries Society, 2009. http://dx.doi.org/10.47886/9781934874080.ch28.
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<em>Abstract</em>.-In many areas of the North Atlantic, populations of Atlantic salmon <em>Salmo salar </em>are now either in a state of decline or extirpated such that concern over the continued survival of the species has been given more attention in recent years despite large reductions in directed ocean fisheries. Previous investigations have established linkages between ocean climate conditions and variability in abundance or survival. However, one avenue not previously explored considers whether changes in marine food webs owing to ever increasing and unsustainable levels of exploitation on many marine species-the so-called "fishing down marine food webs" hypothesis-could influence survival and abundance of salmon as a result of shifts in trophic position or changes in energy flows. Since Atlantic salmon are opportunistic feeders during the marine life history phase, the species lends itself well to studies associated with marine environmental conditions and food web interactions. Here, we examine long-term variability in the trophic ecology of Atlantic salmon using analyses of stable isotope signatures of carbon and nitrogen (?<sup>13</sup>C and ?<sup>15</sup>N). Signatures were extracted from the marine growth portion of scales of maiden one-sea-winter fish. Data were obtained from nine Canadian and one north European river (Teno) covering periods extending over three to four decades. Significant differences in ?<sup>13</sup>C and ?<sup>15</sup>N signatures were found to exist among rivers, as well as among years within rivers. Trends over time in either ?<sup>13</sup>C or ?<sup>15</sup>N signatures were evident in only a few situations, thus providing little evidence of substantive changes in the trophic ecology of salmon in the North Atlantic. In addition, isotopic signatures were largely invariant in relation to variations in abundance or to various environmental measures characterizing ocean climate conditions in the North Atlantic.
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Juo, Anthony S. R., and Kathrin Franzluebbers. "Major Arable Soils of the Tropics :A Descriptive Grouping Based on Clay Mineralogy." In Tropical Soils. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195115987.003.0011.
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Several pedological soil classification schemes have been developed to classify soils worldwide based on morphological features, stage of weathering, and to some extent their chemical and physical properties. Three soil classification systems are commonly used as research and teaching tools in the tropics, namely, the USDA Soil Taxonomy classification, the FAO/UNESCO World Soil Legends, and the French soil classification system. Brazil, the country with the largest land area in the tropics, has its own national soil classification system. However, soil survey, classification, and interpretation are costly and time-consuming, and few countries in the tropics have completed soil maps that are at a scale detailed enough to be useful to farmers and land users. In the absence of soil information at state, county or farm level, the authors propose a simple descriptive grouping of major soils in the tropics based on clay mineralogy to facilitate discussion on soil management and plant production in the subsequent chapters of this book. Reference to the Soil Taxonomy classification will be made when such information is available. It should be pointed out that the main purpose of this technical grouping is to provide field workers, especially those who are less familiar with the various soil classification systems, with a simple framework for planning soil management strategies. It by no means replaces the national and international soil taxonomy and classification systems that are designed for communication among soil scientists and for more detailed interpretation of soil survey data and land-use planning. This technical scheme classifies major arable soils in the tropics into four groupings according to their dominant clay mineralogy. They are • kaolinitic soils • oxidic soils • allophanic soils • smectitic soils Kaolinitic soils are deeply weathered soils with a sand, loamy sand, or sandy loam texture in the surface horizon and a clayey B horizon (20-60%). Silt content is low (< 20%) throughout the profile. Kaolinite (> 90%) is the dominant mineral in the clay fraction. These soils have an effective CEC of less than 12 cmol/kg of clay in the lower B horizon. Kaolinitic soils have a relatively high bulk density, especially in the clayey subsoil horizons (> 1.40 Mg/m3). The structure of the subsoil horizons is usually massive or blocky.
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"Nutrients in Salmonid Ecosystems: Sustaining Production and Biodiversity." In Nutrients in Salmonid Ecosystems: Sustaining Production and Biodiversity, edited by Patrick A. Slaney, Bruce R. Ward, and James Craig Wightman. American Fisheries Society, 2003. http://dx.doi.org/10.47886/9781888569445.ch9.
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<em>Abstract.</em>—Oligtrophic streams are ubiquitous throughout coastal British Columbia, and thereby, significant nutrient influx can be provided externally via salmon carcasses. At the Keogh River on northern Vancouver Island, experimental nutrient addition was conducted from 1983 to 1986 to examine if potential increases in trophic productivity may augment growth and production of salmonid smolts. Subsequently, an applied treatment was conducted over the past decade at the infertile Salmon River to offset intensive logging impacts and to accelerate colonization of steelhead trout <em>Oncorhynchus mykiss </em>of headwater reaches above a hydroelectric diversion. The two rivers were treated with agricultural (dry, later liquid) fertilizers, while upstream control reaches were untreated. At Keogh, inorganic P and N were introduced to produce target soluble phosphorus concentrations of 10–15 mg per L, and N loadings of 50–100 mg per L over the four years of nutrient addition. Average peak algal biomass as chlorophyll <em>a </em>increased 5–10-fold in response to nutrient addition. Geometric mean weights of steelhead trout and coho salmon <em>O. kisutch </em>fry within several treated reaches were 1.4–2.0-fold higher than the control, and mean weights of steelhead parr were 30–130% greater in the three treated reaches. Average steelhead smolt yield in three brood years increased 62% (peak, 2.5-fold in 1987) over prefertilization years; yet there was no increase in average smolt size because mean smolt age was reduced by about one year. There were corresponding increases in returning adults and reported catches by steelhead anglers at the Keogh River, compared with trends at an adjacent river fishery. The response of coho smolts to nutrient addition was less marked, or a suggested 21% increase in numbers (<EM>P </EM>< 0.1) with no change in size, although results were moderated by production of coho smolts from several untreated tributaries and small lakes. At the upper Salmon River, where nutrient targets were reduced to one-third that of the Keogh, nutrient addition was associated with 3–7-fold higher benthic insect density in treated reaches than controls, and 2–3-fold greater mean weights and biomass of steelhead and rainbow trout in treated index sites than upstream, unfertilized sites. Over the decade, estimated numbers of steelhead parr and smolt migrants at the Salmon River diversion increased from about 1,500 to 8,000. The results at the Salmon River confirmed those of the Keogh and indicated that lower-level nutrient addition can produce a similar positive trophic response.
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Stein, Bruce A., and Larry E. Morse. "A Remarkable Array: Species Diversity in the United States." In Precious Heritage. Oxford University Press, 2000. http://dx.doi.org/10.1093/oso/9780195125191.003.0009.
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The Carolina hemlock (Tsuga caroliniana) survives in just a few rocky streambeds along the lower slopes of the Blue Ridge Mountains. Other species of hemlock abound across the United States, but none bear a close resemblance to this particular tree. The closest relatives of the Carolina hemlock, in fact, survive in only one other forest on Earth, some 7,000 miles away in Hubei province of eastern China. The forests of eastern Asia and eastern North America are so similar that if you were suddenly transported from one to the other, you would be hard-pressed to tell them apart. In the swift mountain streams rushing past these seemingly displaced hemlocks live a number of small, colorful fish known as darters. Darters are found only in North America and have evolved into a prolific variety of fishes. Up to 175 species inhabit U.S. waters, including the famous snail darter (Percina tanasi), which brought endangered species issues to the fore when it held up construction of the Tellico Dam on the Little Tennessee River. How is it that these two organisms, hemlock and darter, one with its closest relatives on the other side of the globe and the other found nowhere else in the world, came to be living side by side? Just how many plants and animals share the piece of Earth that we know as the United States of America? Why these and not others? These are central questions for understanding the diversity of the nation’s living resources. The United States encompasses an enormous piece of geography. With more than 3.5 million square miles of land and 12,000 miles of coastline, it is the fourth largest country on Earth, surpassed only by Russia, Canada, and China. The nation spans nearly a third of the globe, extending more than 120 degrees of longitude from eastern Maine to the tip of the Aleutian chain, and 50 degrees in latitude from Point Barrow above the Arctic Circle to the southern tip of Hawaii below the tropic of Cancer. This expanse of terrain includes an exceptional variety of topographic features, from Death Valley at 282 feet below sea level to Mt. McKinley at 20,320 feet above sea level.
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"Challenges for Diadromous Fishes in a Dynamic Global Environment." In Challenges for Diadromous Fishes in a Dynamic Global Environment, edited by Timothy D. Jardine, Jean-Marc Roussel, Sean C. Mitchell, and Richard A. Cunjak. American Fisheries Society, 2009. http://dx.doi.org/10.47886/9781934874080.ch27.
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<em>Abstract</em>.—We used stable isotope analysis in an attempt to detect marine subsidies from anadromous fish to freshwater benthos in four river systems draining to the Atlantic Ocean. Benthic invertebrates in the West River, Nova Scotia, Canada, had elevated d<sup>13</sup>C, d<sup>15</sup>N, and d<sup>34</sup>S values in a downstream reach that suggested consumption of marine-derived organic matter from spawning blueback herring <em>Alosa aestivalis</em>. In Doctor’s Brook, Nova Scotia, the arrival of rainbow smelt <em>Osmerus mordax </em>to spawn led to rapid increases in the d<sup>13</sup>C and d<sup>15</sup>N of a predatory stonefly (Perlidae), but lower trophic levels (mayflies and biofilm) showed inconsistent responses. Sculpin <em>Cottus </em>sp. showed no evidence of predation on Atlantic salmon <em>Salmo salar </em>eggs in Catamaran Brook, New Brunswick, Canada or the Scorff River, Brittany, France. These analyses suggest that marine organic matter subsidies, in the form of direct consumption of eggs and/or carcasses, are important in streams with concentrated spawning activity such as by alosid and osmerid species, whereas carbon and nitrogen contributions from more sparse spawning species such as by Atlantic salmon may be minimal.
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Araya-Vergara, José. "Ocean Coasts and Continental Shelves." In The Physical Geography of South America. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195313413.003.0023.
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Suess (1900) provided the first scientific treatment of the South American coast from a tectonic perspective when he distinguished between the Atlantic and Pacific structural styles on opposite sides of the continent. Inman and Nordstrom (1971) later complemented this approach by relating these styles to the concepts of plate tectonics that had emerged during the 1960s. Useful keys to understanding South American coastal processes and sediment supplies were then offered by Davies (1977) and Potter (1994), respectively, while regional accounts of South American coastal landforms were made by specialists in books edited by Bird and Schwartz (1985) and Schwartz (2005). Clapperton (1993) reviewed Quaternary coastal morphogenesis. Coastal sites of scientific importance and historical coastline changes were discussed by Bird and Koike (1981) and Bird (1985). This chapter focuses on the principal factors involved in coastal evolution and morphogenesis, describes key regional landforms, and proposes a new analytical perspective for South America’s coasts by introducing a hierarchical system within coastal groups. The main coastline of South America is approximately 31,100 km long, of which 10,400 km face the Pacific Ocean, 16,700 the open Atlantic Ocean, and the remaining 4,000 km the more sheltered Caribbean Sea. Of the total length, approximately two-thirds lie within the tropics, ensuring that physical and ecological responses to ocean-atmosphere circulation systems involving the Intertropical Convergence Zone dominate these coasts. The remaining one third of the coast beyond the tropics is dominated during part or all of the year by temperate westerly conditions, which become increasingly cool and stormy toward the continent’s southern tip. The origins of the present coast reflect the tectonic forces that have affected the South American plate over the past 200 million years, augmented by relative sea-level changes associated with changing global (eustatic) ocean volume and regional (isostatic) crustal adjustments. The Atlantic coast of South America owes its broad outline to the separation of the continent from neighboring parts of Gondwana that began more than 200 Ma (million years ago). The Pacific and Caribbean coasts have a more complex history, related to the progressive interaction of the westwardmoving South American plate with four oceanic plates with which it has come into contact).
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"Proceedings of the First International Snakehead Symposium." In Proceedings of the First International Snakehead Symposium, edited by Hae H. Kim, Jason A. Emmel, and Quinton E. Phelps. American Fisheries Society, 2019. http://dx.doi.org/10.47886/9781934874585.ch4.
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<em>Abstract.</em>—Relative weight and size structure indices are useful tools for fish biologists to characterize fish condition and fish size structure. However, a standard-weight (<em>W<sub>s</sub></em>) and size structure indices do not currently exist for Northern Snakehead <em>Channa argus</em>. We complied length-weight data from 4 established populations of Northern Snakehead in North America across five states and four drainages. We used the regression-line-percentile (RLP) method to develop a standard-weight equation for Northern Snakehead. The RLP method uses the 75th percentile as a benchmark for standard weight. Based this approach, we propose a metric standard-weight equation as log<sub>10</sub>(<em>W<sub>s</sub></em>) = –5.142 + 3.0418 * log<sub>10</sub> (TL) with a minimum length of 200 mm; <em>W<sub>s</sub> </em>is weight in grams and TL is total length in millimeters. For calculating proportional size distribution (PSD) we proposed the following length categories: stock, 190mm (7.5 in); quality, 340 mm (13 in); preferred, 420 mm (16.5 in); memorable, 550 mm (22 in); and trophy, 700mm (27.5 in). The population level indices developed in this study will provide fish biologists another set of tools to describe invasive Northern Snakehead populations in North America.
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"Conservation, Ecology, and Management of Catfish: The Second International Symposium." In Conservation, Ecology, and Management of Catfish: The Second International Symposium, edited by ROBERT S. GREENLEE and CATHERINE N. LIM. American Fisheries Society, 2011. http://dx.doi.org/10.47886/9781934874257.ch30.
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<em>Abstract</em>.—Introduced blue catfish <em>Ictalurus furcatus</em> populations in tidal rivers of the Atlantic slope support important recreational and commercial fisheries, with the James River trophy fishery being nationally recognized. During the period 2001–2008, low-frequency (15 pulses/s) pulsed DC electrofishing was used to sample blue catfish in tidal fresh-oligohaline sections of the James, Mattaponi, Pamunkey, and Rappahannock River systems; 54,174 blue catfish were collected, and 4,660 of these were aged using otoliths. Mean catch per unit effort (CPUE) was generally high (ranging from 223 to 6,106 fish per hour). Trends of increasing CPUE through time occurred in the James (839–4,449 fish per hour) and Rappahannock (1,400–6,106 fish per hour) rivers, and differences in CPUE were detected among rivers. Temporal shifts in growth (mean length at age) were observed, with growth slowing for all ages in the Pamunkey River and slowing for older ages in the Mattaponi (ages 9–13) and Rappahannock (ages 8–12 and age 14) rivers. In the Pamunkey and Rappahannock rivers, a negative relationship existed between growth (mean length at age 10) and density (CPUE). Although density increased dramatically in the James River, growth remained stable. Growth varied among rivers; by the end of the study, mean total length at age 10 ranged from 416 mm in the Rappahannock River to 675 mm in the James River. Growth through age 15 fi t linear models, as opposed to the von Bertalanffy nonlinear curve. In three of the four populations, the maximum age sampled increased in each succeeding survey year, and the maturing of all four populations was reflected in concurrent increases in size distributions. Recruitment was variable, with coincident strong and weak year-classes occurring in all four populations—an implication that landscape-level environmental variables play a role in determining recruitment success. In three of the four populations, patterns in year-class strength persisted, with correlation of catch-curve residuals from surveys separated by time. Approximately 35 years poststocking in the James and Rappahannock rivers and 25 years poststocking in the Mattaponi River, these populations had not yet reached equilibrium. It is unknown what the dynamics of blue catfish abundance, growth, and survival will be in the long-term in these rivers, leaving uncertainty regarding the future of the fisheries the populations support, as well as unanswered questions related to potential effects on other species.
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Whiteman, C. David. "Mountain Climates of North America." In Mountain Meteorology. Oxford University Press, 2000. http://dx.doi.org/10.1093/oso/9780195132717.003.0008.
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The basic climatic characteristics of the major mountain ranges in the United States—the Appalachians, the Coast Range, the Alaska Range, the Cascade Range, the Sierra Nevada, and the Rocky Mountains—can be described in terms of the four factors discussed in chapter 1. The mountains of North America extend latitudinally all the way from the Arctic Circle (66.5°N) to the tropic of Cancer (23.5°N) (figure 2.1). There are significant differences in day length and angle of solar radiation over this latitude belt that result in large seasonal and diurnal differences in the weather from north to south. Elevations in the contiguous United States extend from below sea level at Death Valley to over 14,000 ft (4270 m) in the Cascade Range, the Sierra Nevada, and the Rocky Mountains. Several prominent peaks along the Coast Range in Alaska and Canada (e.g., Mount St. Elias and Mount Logan) reach elevations above 18,000 ft (5486 m). Denali (20,320 ft or 6194 m) in the Alaska Range is the highest peak in North America. The highest peak in the Canadian Rockies is Mt. Robson, with an elevation of 12,972 ft (3954 m). The climates of the Coast Range, the Cascade Range, and the Sierra Nevada, all near the Pacific Ocean, are primarily maritime. The Appalachian Mountains of the eastern United States are subject to a maritime influence from the Atlantic Ocean and the Gulf of Mexico, but they are also affected by the prevailing westerly winds that bring continental climatic conditions. Only the climate of the Rocky Mountains, far from both the Pacific and Atlantic Oceans, is primarily continental. Each of the mountain ranges is influenced by regional circulations. For example, the Appalachians are exposed to the warm, moist winds brought northward by the Bermuda-Azores High and to the influence of the Gulf Stream. Similarly, the Coast Range feels the impact of the Pacific High, the Aleutian low, and the Japanese Current. A mountain range, depending on its size, shape, orientation, and location relative to air mass source regions, can itself affect the regional climate by acting as a barrier to regional flows.
Conference papers on the topic "Fourth trophic level"
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Li-Jones, Xu, Paul F. Penko, Sherry Williams, and Cliff Moses. "Gaseous and Particle Emissions in the Exhaust of a T700 Helicopter Engine." In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27522.
Full textAbstract:
Emissions were measured for four fuels and six combinations of fuels and additives in the exhaust of a T700-GE-700 helicopter engine. The test matrix consisted of three engine power settings: idle, continuous, and maximum continuous. The four fuels were JP-5, F-76, and two synthesized fuels from the Fischer-Troph process, one containing zero sulfur and zero aromatics (synthetic A), and a second containing zero sulfur and 14 vol% aromatics (synthetic B). The JP-5 was also tested with a solvent that increased the aromatic content, and seeded with copper to simulate contamination from shipboard fuel-distribution systems. The JP-5 and F-76 were also tested with an additive commonly used to increase thermal stability. Carbon-monoxide (CO) emission-indices (EIs) for the JP-5 ranged from 53.4 g/kg at idle to 2.3 g/kg at maximum power. The EI of total hydrocarbons (THCs) ranged from 3.9 g/kg to 0.13 g/kg over the same power settings. The effect of the various fuels and additives on the emissions of CO and THCs was negligible (at the 95% confidence level), except at maximum power where CO from the F-76 was about 25% higher, and from the first synthetic, about 16% lower than the JP-5. At all power settings, the CO for JP-5 with the thermal-stabilizer additive were consistently lower by about 12%. Particulate matter was measured and displayed nearly log-normal distributions with a single-mode for all fuels tested. In all cases, count median-diameters (CMDs) ranged from about 20 to 60 nm, and increased with power setting. Mass emissions also increased with power setting. On a number basis, emissions ranged from 1.6 × 1013 to 1.7 × 1015 particles/kg, and increased with power setting for most of the fuels and fuel-additive combinations. The CMD and mass emissions for the JP-5 ranged from 30 to 50 nm and 0.06 to 0.49 g/kg from idle to maximum power. The F-76 produced the largest CMDs and highest particle mass at all conditions, with a CMD of 60 nm and mass emissions of 0.77g/kg occurring at maximum power. Synthetic A fuel produced the smallest particle CMDs and lowest particle mass at all power settings. The thermal-stability additive and variations in aromatic content, and copper particles, did not significantly affect the particle emissions. Particle mass measured with a filter-gravimetric method correlated well with the particle volume calculated from the measured number size-distributions, where the correlation yielded a particle density of 1000 kg/m3.