History of Ecological Sciences, Part 59: Niches, Biomes, Ecosystems, and Systemsстатья из журнала
Аннотация: Hagen and I use approximately the same material, but we each tell two different stories about ecosystem ecology. His approach is to embed the ecosystem concept in a history of American and English ecology. My approach has been to focus on the concept and the individuals contributing to concept development and then to consider causal factors that led to pattern we observe. Joel Hagen is a historian and comes to the story from outside…I was a participant in the story and approach it from within. Hagen (1992) began with Charles Darwin (1859), and Golley with Anton Kerner (1863). French historian of ecology Jean-Marc Drouin wrote his doctoral dissertation at Université Paris on La naissance du concept d'ecosysteme (1984a), which focused on key papers by Forbes (1880), Tansley (1935), and Lindeman (1942). As an appendix to his narrative, Drouin translated all three papers into French. He published a lengthy summary (1987), and his L'écologie et son histoire (1991, edition 2, 1993) incorporated discussions from his dissertation within a broader context. "Mac" McIntosh surveyed the history of the ecosystem concept and also of systems ecology in The Background of Ecology (1985:193–241), with numerous references. A chapter in Robert O'Neill et al., A Hierarchical Concept of Ecosystems (1986:20–34) discussed how ecologists have viewed ecosystems—a discussion organized topically, not chronologically. Chunglin Kwa surveyed aspects of American systems ecology and American participation in the International Biological Program (IBP). Robert Ricklefs and Gary Miller published an introductory ecology textbook which has a historical perspective in a chapter on ecosystems (2000:171–184; a history omitted from the brief version—Ricklefs 2008). Christian Lévêque's Ecology from Ecosystem to Biosphere (2003) also contains historical discussions. Robert Whittaker's Classification of Natural Communities (1962) is a helpful reference work, which discussed numerous studies. The history summarized here includes the following: niche quotations from later 1800s and early 1900s; pre-biome background from the 1800s and early 1900s; biome history beginning with Clements (1916); two ecosystem foreshadowings (Lotka 1925, Elton 1927); ecosystem history beginning with Tansley (1935), significantly expanded in scope by Lindeman (1942); and systems ecology arising out of radioecology, after World War II, when development of computers enabled ecologists to investigate complex aspects of ecosystems. What could computers add to understanding ecosystems? That was a challenge of the IBP, with controversial results. Both EP Odum's Georgia Institute of Ecology and F.H. Bormann and G.E. Likens' project at Hubbard Brook were scenes of simultaneous group research outside IBP that were less controversial. IBP was one origin of "big ecology." A good beginning for this discussion is Darwin's Origin of Species by Means of Natural Selection (1859). Its importance lies primarily in the new understanding arising from his scientific revolution, but his book included a relevant discussion of a food chain (Darwin 1859:73–74, Egerton 1973:341–342, 2007:52–53, Hagen 1992:1–2). It began with a plant, red clover, and ended with a predator, domestic cats. Although Darwin cited one biological reference concerning humble bees which pollinated red clover, he had not conducted a close study of this food chain, and not surprisingly a later commentator (McAtee 1947) found two aspects of it more ambiguous than Darwin had realized. It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us. This comment invites readers to delve into the complexities of nature with Darwin's arguments in mind. However, it also illustrates his own general awareness of biotic communities, which he never explicitly explored. Austrian botanist Anton Kerner (1831–1898) had a childhood interest in plants (Stafleu and Cowan 1979:II:525–530, Hagen 1992:1–2), but he nevertheless obtained a doctorate in medicine and surgery from the University of Vienna (1854). A cholera epidemic in 1855 ended his interest in a medical career; he turned to botany and became professor at Josef's Polytechnicum at Ofen, Hungary (Stapf 1898, Egerton 2013b:341–342). In 1861, he moved to the University of Innsbruck, and in 1878, he returned to the University of Vienna. He had been knighted in 1877 and had then added "von Marilaun" to his name. Das Pflanzenleben der Donaülalnder (1863, English, 1951) was his first notable work, in which he described about two dozen "formations" in the Danube Basin, taking the term from August Grisebach (1814–1879) and using German language terms for formation names. He aspired to describe the origin, development, maturation, and decline of each formation (Kerner 1951:10). He was interested in why trees could invade prairie only along rivers or in lowland fens, and he compared treeless prairie with treeless mountain tops. For both, tree growth was only about two months a year, limited on prairies by drought and on mountain tops by frost (Kerner 1951:26–27). His most important work was Das Planzenleben (1888, English, 1894), which discussed plant communities: Golley (1993:17–18, quoted from the translation). Danish botanist Johannes Warming (1841–1924) attended the University of Copenhagen and eventually became professor of botany and director of the botanic garden there (1886–1911). He took leave from his education to become secretary to zoologist P.W. Lund for three years, 1863–1866, in Brazil, where Warming studied tropical vegetation, and that became the subject of two of his extensive publications (Müller 1976, Egerton 2013b:346–347). He also published extensively on the Danish flora. However, he is most remembered for his Planzesamfund: Grundträk af den okologiske Plantesgeografi (1895, German 1896, Russian 1901, English 1909), which lacked illustrations, had a lengthy bibliography, and served as the first textbook of plant ecology. The title of the Danish and German editions included "ecological plant ecology," but that phrase was dropped in the English language title and replaced with "An Introduction to the Study of Plant-Communities." His conceptual organization of the book is explained in sections 1–3. Section 1, Oecological Factors and Their Actions, discussed climate, soil, and effects of vegetation and of animals. Section 2, Communal Life of Organisms, discussed symbiosis, mutualism, and commensalism. Section 3, Adaptations of Aquatic and Terrestrial Plants, Oecological Classification, explained a basic distinction between aquatic and terrestrial species, then addressed ecological classification: Among land plants, he distinguished between xerophyte and mesophyte "communities." However, he then did not subdivide his chapters under these headings, and instead provided ten sections on "formations" based on either moisture or soil: hydrophytes (aquatic), helophtes (marsh), oxylophytes (sour soil), hylophytes (saline), lithophytes, psychrophytes (cold soil), psammophytes (sand, gravel), eremophytes (desert, steppe), chersophytes (waste), psilophytes (savannah), then two formations based on species types (sclerophyllous, coniferous), and finally, section XVI on mesophytes. Warming used the term formation to distinguish ecological groups because Grisebach had used it in 1838 and other botanists had adopted it since then. His last section (XVII) was "Struggle between Plant Communities," which title might indicate he used the terms "community" and "formation" as synonyms, as he wrote (1909:348): "Hitherto we have treated plant-communities as if they were static entities…" He used the term association to indicate differences within a formation in different locations, as one coniferous association of pines and another of firs. Some terms he used persist, but others do not. Warming was succeeded as Professor of Botany at the University of Copenhagen by one of his pupils, Christen Raunkiaer (1860–1938). Raunkiaer was born on a farm named Raunkiaer and took that name for his family name. Almost all of his research concerned what he called life forms, which could be used to compare plant formations of different regions. To some extent, he quantified aspects of Warming's plant ecology. The key to his approach was the part of a vascular plant species that survive the unfavorable season of the year. He published a one-page article defining five types of possible alternatives (1903, English, 1934a): Phanerophytes (surviving buds or shoot apices borne on negatively geotropic shoots projecting in the air); Chamaephytes (surviving buds or shoot apices borne on shoots very close to ground); Hemicryptophytes (surviving buds or shoot apices situated in soil surface); Cryptophytes (surviving buds or shoot apices buried in ground at a distance from surface that varies in different species); and Annuals or Therophytes (plants of summer or of favorable season). He then listed subtypes under these headings. It is difficult to see how readers could use his scheme until he wrote a 103-page monograph of explanations and examples (1907, English, 1934b). Traditional scholarship indicated that the niche concept arose with Joseph Grinnell and H. S. Swarth's account of birds and mammals in the San Jacinto area (1913) and Grinnell's paper on California's thrashers (1917) and, seemingly independently, in Charles Elton's textbook, Animal Ecology (1927). These sources retain their importance, but David Gibson-Reinemer (2015) found a number of uses of the term, 1833–1899, in biological contexts. What conclusions should we draw? Ernst Haeckel had named and defined a new science, ecology (1866, II:286; Egerton 2012:198–200, 2013a:226), but awareness of it hardly penetrated the English-speaking world before the 1890s. Niche was a common word in the 1800s, and its usage in a biological context was without theoretical implications. For example, Gibson-Reinemer (2015:330) cited a book review by Alfred Russel Wallace (1882) of a book by Grant Allen in which Allen (1881) stated: "the nettle has made itself a niche in nature along the bare patches" (in Wallace 1882:381). Neither Allen nor Wallace commented on "niche" in this context. However, theoretical implications of this concept began to emerge during the early decades of the 1900s. Skipping over Herbert Spencer's conjectural essay, "The Social Organism" (1860), which Egerton (1973:342–343), Hagen (1992:3–7), and Golley (1993:36) discussed as an influence on Illinoisan Stephen Forbes (1844–1930), the next noteworthy step was taken by Forbes (1880), who was a founder of animal ecology in the United States (Croker 2001, Egerton 2014:64–65). He was both a college professor and Illinois State Biologist who regularly studied fish and insects, and sometimes birds. His many natural history studies (H. C. Oesterling compiled his 29-page bibliography, published in Howard 1932, Croker 2001:212–217 has a concise bibliography) were relevant for ecology, 17 of which are reprinted (Forbes 1977). He published his first essay on general ecology in 1883, and in 1887, he delivered a talk for which he is remembered, The lake as a Microcosm (reprinted 1925 and later). It seems fair to say he had the idea of an ecosystem in 1887, without the name, for he discussed the physical environment as well as animals in specific detail, from his own studies. He clearly had not studied aquatic plants; he mentioned a variety of multicellular species, but without specific details (Forbes 1925:540–542), and he did not even mention phytoplankton. His 1887 essay (as reprinted, 1925) was appreciated by American ecologists but was perhaps unknown abroad. Forbes continued publishing until the year of his death, but without producing another general ecological essay. Europe's foremost limnologist after François Alphonse Forel (1841–1912) was August Thienemann (2008) (Thienemann 1959). Coincidentally, Thienemann also used the term microcosm, though as a synonym for "biocoenosis" (1925), a more biologically specific term (quoted in English translation in Golley 1993:39). Meanwhile, two American plant ecologists rose to prominence, Connecticut native Henry C. Cowles (1869–1939) and Nebraskan Frederic E. Clements (1874–1945). Cowles earned his Ph.D. at the University of Chicago and remained there (Hagen 1992:16–20, Burgess 1996:31–32, Cassidy 2007, Egerton 2013b:360–363, 2015:1–3) and Clements earned his at the University of Nebraska (Burgess 1994:103–118, 1996:26–27, Hagen 1992:20–28, Egerton 2013b:358–360, Egerton 2015:5–6). Each was influenced by European forerunners, and each went his own way, but both studied plant communities and community succession. Cowles wrote a notable Ph.D. dissertation, which he published in articles in 1899 and 1901a,b. Afterward, he sometimes published, as The Causes of Vegetative Cycles (1911), but his main efforts went into teaching new plant ecologists. Clements spent a few years teaching, but preferred research, which he eventually conducted at research stations of the Carnegie Institution of Washington. His Plant Succession (1916) was a very substantial work that dominated American plant ecology for over four decades (McIntosh 1985:76–85, Drouin 1994, Egerton 2009). He argued that if plant communities are destroyed, new vegetation evolves by succession determined by climate to an inevitable, predictable climax (Drouin 1984b, Larrère 1993). However, Illinoisan plant ecologist Henry Gleason (1882–1975) challenged Clements in The Structure and Development of the Plant Association (1917) and again in The Individualistic Concept of the Plant Association (1926), challenging the hypothesis of an inevitable succession to a predictable climax. Only after World War II did his perspective gain a significant following (Nicolson 1990, Nicolson and McIntosh 2002). Both Cowles and Clements appreciated the influence of inanimate environments upon plant communities. A step toward the ecosystem concept, which Tansley acknowledged, was Frederic Clements's "biome" concept, meant to encompass both plants and animals of a given habitat. In his opening address at the first meeting of the Ecological Society of America, in 1916, "The Development and Structure of Biotic Communities," Clements introduced the term "biome" as a synonym of "biotic community" (Croker 1991:65). Previously, in Research Methods in Ecology (1905:292–299), he had discussed prairie, forest, and alpine "formations," which could be subdivided into communities. Since the scope of that book was not just plant ecology, these formations implicitly included animals. In 1913, botany graduate student Arthur G. Vestal (1888–1962), under Cowles at the University of Chicago (Ph.D. 1915), published on the biotic association of plants and animals on Illinois sand prairies; Clements and Victor Shelford (1877–1968) later decided that all three of them had been working toward a biotic community concept "more or less independently" at the same time (Croker 1991:66). In retrospect, ecologists have judged the biome concept a modest advance toward the ecosystem concept. By 1919, Clements had placed a series of quadrats on Pike's Peak to study biomes, while Shelford was studying shallow marine communities at Puget Sound (Croker 1991:69–71). Shelford visited Clements's Alpine Laboratory in August 1923, and in 1925, Clements visited Shelford in Urbana, and they agreed to work together to advance the understanding of biomes. There were some disagreements as they attempted to cooperate, and "The most serious trial to the partnership of Clements and Shelford was always the conflict between Clements's philosophical predilections and Shelford's practicality" (Croker 1991:72). Meanwhile, Shelford organized and supervised a seven-year project to describe the natural areas of the Americas, from the Amazon in the south to the Arctic in the north. Shelford recruited 118 coauthors who contributed to a Naturalist's Guide to the Americas (1926), which he edited. However, instead of using Clements's term "biome," he used the terms "biota" and "biotic," without defining them. The Naturalist's Guide was a notable achievement for ESA during its first decade, though a descriptive guide without theoretical content. That guide was a helpful reference when Clements and Shelford published Bio-Ecology (1939), a synthesis of their parallel researches. During the twelve years in which they collaborated, Shelford visited Pike's Peak seven times and Clements visited Urbana six times (Croker 1991:71). Bio-Ecology was suitable for a college textbook in ecology, and over 5000 copies were sold by 1958 (Croker 1991:90). The general concepts were illustrated by American examples; nevertheless, South African plant ecologist John Phillips, focus of Tansley's 1935 attack, came to Urbana to read the manuscript before publication. Phillips was rather critical, and Shelford made changes; Clements offered to delete his discussion of the "complex organism concept for the biome," but Shelford did not press him to do so (Croker 1991:88–89). It seems to be the first general ecology textbook, as opposed to earlier ones on plant ecology and animal ecology. The most significant review was Evelyn Hutchinson's in Ecology. He criticized the book's neglect of biogeochemistry and metabolic aspects of the community (Hutchinson 1940). Undaunted by Hutchinson's complaint, Shelford continued along the research path he had been following, beginning with the Naturalist's Guide of describing North American biomes. In the Preface to The Ecology of North America (1963:vii), he stated that there had been gaps of knowledge in certain regions, until he had graduate students study them for Ph.D. dissertations: "hemlock-cedar forest in Oregon, the cold desert in Utah, the Rocky Mountain forest and pinyon-juniper in Arizona, the mountain forest and oak brush in Utah, the mountain forest in Maine, the deciduous forest in Illinois, and the tall-grass grassland in Illinois." He himself had done additional studies in Manitoba tundra, Mississippi flood plain in western Tennessee, and in central Illinois forests. He devoted two paragraphs to the ecosystem concept (Shelford 1963:3), but this was a descriptive work in which metabolic aspects of communities were not included. "Shelford was arguably the only person of his time with the experience and the audacity to write this book" (Croker 1991:157), and reviews were favorable. It is well illustrated and documented and became a valuable reference work. In their chapter 9, "The Ecosystem Concept," Ricklefs and Miller (2000) argued (section 9.4) that "A. J. Lotka espoused a thermodynamic view of ecosystems" (2000:176), referring to Lotka's Elements of Physical Biology (1925). Later (section 9.6), they argued that "Lotka described the regulation of ecosystem function in terms of ecological relationships of the component populations" (2000:178). Their statements need qualifications, because Arthur Tansley only named and defined "ecosystem" in 1935. American demographic statistician Alfred Lotka (1880–1949) was in the odd position of writing a book for an audience, biologists, whom he barely knew, and who generally lacked mathematical education (Gridgeman 1973, Israel 1988, Egerton 2014:73). In Lotka's book, one finds chapters entitled "The Fundamental Equations of the Kinetics of Evolving Systems" (chapter 6) and "Inter-species Equilibrium" (chapter 13). Clearly, Lotka did not attempt to define an ecosystem, but one might argue that he had a sense of plants and animals functioning in an inanimate environment. His goal was to instruct how to make calculations in biological investigations, not to define new concepts. However, he perhaps first diagramed the natural cycles of common elements. Lotka's audience emerged after his book appeared. English animal ecologist Charles Elton (1900–1991) was educated at Oxford University and spent his career there (Cox 1979, Crowcroft 1991, Burgess 1996:39, Southwood and Clarke 1999). He participated in three Oxford expeditions to Spitsbergen. He was impressed by transfer of nutrients from sea to land when sea birds brought fish to their young, and he constructed a diagram showing a complex food web to illustrate this (Summerhayes and Elton 1923, reprinted in Elton 1927:58). That diagram is also reproduced by Golley (1993:44) and Egerton (2007:58). Elton had titled the diagram "Food-cycle among the Animals on Bear Island"; Golley retitled it "The nitrogen cycle on the arctic island, Bear Island." Lotka's nitrogen cycle diagram, illustrated above, clearly owed nothing to Elton's diagram. However, it is not just his diagram that won for Elton notice in histories of the ecosystem concept (Hagen 1992:index, Golley 1993:index, Ricklefs and Miller 2000:175–176). He also seemed to have had an implicit awareness of ecosystems without naming and defining them. The chapters in his landmark Animal Ecology (1927) included these titles: The Distribution of Animal Communities, Ecological Succession, Environmental Factors, and The Animal Community. The niche concept figured prominently in his discussion of animal communities (1927:63–68). He has often been identified as one of two founders of that concept, the other being the American vertebrate zoologist Joseph Grinnell (1917). However, as mentioned above, niche was a common noun during the 1800s, and naturalists and biologists used it in both the United Kingdom and the United States. Daniel Gibson-Reinemer (2015) collected a number of examples of that usage during the 1800s. As editor of the Journal of Ecology, Arthur Tansley (1871–1955) received articles by John Phillips on The Biotic Community, and Succession, Development, the Climax and the Complex Organism: an Analysis of Concepts, which Tansley published (1931, 1934–1935). He nevertheless decided that these articles were misguided (influenced by Clements's misguided ideas), and he attacked them in The Use and Abuse of Vegetational Concepts and Terms (1935), which he published in a special issue of the American journal, Ecology, dedicated to Cowles. Tansley wanted to offer an alternative term to Phillips' "complex organism" (Hagen 1992:82–87, Golley 1993:31–34, Ayres 2012:135–138, Egerton 2013b:355–357). His alternative was "ecosystem," which included inanimate environment plus plants and animals which "are the basic units of nature" that exist in "the most various kinds and sizes," and which "show organization, which is the inevitable result of the interactions and consequent mutual adjustment of their components" (Tansley 1935:299–300). His understanding of ecosystem placed it in a series of systems from atom to universe. Tansley did not use his concept to lead plant ecology in a new direction (Sheail 1987). He merely wanted to replace Phillips' muddled ideas. Nor were contemporary ecologists set on fire by reading his paper. The environmental emphasis of limnologists Birge, Juday, and Rawson (Egerton 2016:267–268) was coincidentally useful to ecosystem studies, but the first significant use of the term "ecosystem" was in Raymond Lindeman's The Trophic-Dynamic Aspect of Ecology (1942), which Hutchinson, Lindeman's postdoctoral advisor, published in Ecology after Lindeman's early death. Minnesotan Raymond Lindeman (1915–1942) graduated from Park College in Missouri (1936), then earned a Ph.D. (1941) at the University of Minnesota, studying under zoological limnologist Samuel Eddy and plant ecologist William Cooper (Cook 1977, Hagen 1992:87–94, Golley 1993:48–56, Burgess 1996:66, Brady 2008, Slack 2010:149–151). For his dissertation, Lindeman studied limnology and succession for five years at Cedar Bog Lake, near the university. On a postdoctoral fellowship, Lindeman went in September 1941 to Yale to work under Hutchinson. He was already familiar with some of Hutchinson's writings, and he had corresponded with him and with one of his students, Edward Deevey. Lindeman's project was to revise and expand the last chapter in his dissertation into a scientific article, under Hutchinson's guidance. In this article, he explained (Lindeman 1942:399): "The trophic-dynamic viewpoint…emphasizes the relationship of trophic or 'energy-availing' relationships within the community-unit to the process of succession." He included a diagram of the trophic–dynamic relationships (1942:401) that was influenced by a diagram which Thienemann (1926:57) had published. Lindeman's conclusions included: "The percentage loss of energy due to respiration is progressively greater for higher levels in the food cycle" and "Productivity and efficiency increase during the early phases of successional development. In lake succession, productivity and photosynthetic efficiency increase from oligotrophy to a prolonged eutrophic stage-equilibrium and decline with lake senescence…" (1942:415). Hutchinson's endorsement undoubtedly encouraged American ecologists to take seriously arguments by Lindeman, who was virtually unknown to them. The priority Gene gave to groups over individuals as agents of social change reflected his father's tendency to attribute human behavior to social structures; and the priority he gave to the ecosystem over the ecosystem's individual components reflected his father's advice to look at "the big picture." EP Odum dedicated one of his textbooks, Ecology (1963), to the memory of his father, and HT Odum did the same with his rather revolutionary textbook, Environment, Power and Society (1971). As a youth, EP Odum was interested in wildlife, especially birds, and life in streams (Craige 2001:12–13), while in high school, he visited the North Carolina State Museum in Raleigh, where he met the director, Herbert H. Brimley. "H. H. Brimley and his brother C. S. did more than anyone else to encourage me to develop my interest in birds" (Odum 1949:vi). A close friend of EP Odum was Coit M. Coker, son of Zoology Professor Robert E. Coker. EP Odum and Coit Coker wrote a regular column in the Chapel Hill Weekly on local birds, in which they encouraged readers to plant shrubs attractive to birds (Craige 2001:14). Upon graduating in 1934, the two friends bought a used car and toured scenic parks in the West. After receiving his M.A. degree from UNC in 1936, with a thesis on toadfish embryology (Odum 1936, b), EP Odum taught biology at Case Western Reserve University in Cleveland, 1936–1937, while taking two physiology courses (Craige 2001:22). During the summer of 1937, he banded birds for the U.S. Fish and Wildlife Service and measured heart rates of small birds for a doctoral dissertation at the University of Illinois, under ecologist Charles Kendeigh. EP Odum received his Ph.D. in 1939 and had his dissertation published in Ecological Monographs (Odum 1941). Prof. Kendeigh published a textbook, Animal Ecology (1961), which appeared after EP Odum had published two editions of his famous Fundamentals of Ecology (1953, 1959). Their textbooks are rather different and differ in scope (animals versus general ecology). Odum derived his vision of nature from Clements's theory of the climax formation, or superorganism; Shelford's concept of the biome; Smut's articulation of the characteristics of the whole; Tansley's ecosystem concept; Leopold's definition of land; Lotka's theories of energy transfer; and Lindeman's energetics. Ecologists reading this list of scientists will notice that it includes both holists and reductionists. How did EP Odum reconcile these two perspectives? Ecologist philosopher Donato Bergandi (1995) complained that he did not, and did not notice the contradiction. Bergandi compared the discussion of ecosystem in the three editions of Fundamentals of Ecology and found that "In the second and third editions, the individual organisms disappear and are replaced by 'functional processes'" (1995:156). Bergandi finds it "truly paradoxical that an author as strongly involved in epistemological holism as Odum confines himself to understanding the ecosystem essentially in terms of energy" (1995:166). However, EP Odum may simply have added his brother's methodology to his own previous perspective. Robert O'Neill (2001:3275–3276) criticized EP Odum's ecosystem concept as no longer adequate (without discussing Bergandi's critique). EP Odum went to the University of Georgia in 1940 as an instructor in zoology, where he proved his merits and rose steadily through the ranks to an endowed chain in 1957. In 1951, the Atomic Energy Commission (AEC) decided to build a plant on the Savannah River (SRP), near Aiken SC, to produce tritium, for making nuclear weapons, and it invited the universities of Georgia and South Carolina to submit proposals to make biological inventories on the 250,000-acre reservation. EP Odum and colleagues submitted a proposal for both an inventory and an ecological study of interrelationships (Craige 2001:48–50). The AEC offered each university much smaller grants than they had expected for the study, but EP Odum decided that he could use graduate students for the research and accepted the offer, thus began a long-lasting and important relationship between the AEC and the University of Georgia's research team under EP Odum, which enabled him to increase the number of graduate students his Zoology Department could support and also to hire full-time researchers. EP Odum's research plan was "to use energy flow through biological food chains as a means of linking plants and animals" (Odum 1987, in Craige 2001:52), and radionuclide tracers enabled his teams to quantify movement of matter and energy through ecosystems, and determine the times involved. They
Год издания: 2017
Авторы: Frank N. Egerton
Издательство: Ecological Society of America
Источник: Bulletin of the Ecological Society of America
Ключевые слова: Sustainability and Ecological Systems Analysis, Environmental, Ecological, and Cultural Studies
Открытый доступ: hybrid
Том: 98
Выпуск: 4
Страницы: 298–337