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Defined and described
  "The biome or plant-animal formation is the basic community unit, that is, two separate communities, plant and animal, do not exist in the same area. The sum of plants in the biome has been known as vegetation, but for r animals no similar distinctive term has become current. It is obvvious, however,that the two do notr represent natural divisions of the biotic complex ...
  "The extent and character of the biome are exemplified in the great landscape types of vegetation with their accompanying animals, such as grassland or steppe, tundra, desert, coniferous forest, deciduous forest, and the like. These commonly represent biotic formations or climaxes, which in their general features have been noted by naturalists since the early days of biology....
  "The term biome, as here employed, is regarded as the exact synonym of formation and climax when these are used in the biotic sense." 
With these words Frederic Clements in Bio-ecology  (Clements and Shelford, 1939, p. 20) left on the field of Ecology the second  most enduring (and least controversial) of his terms and concepts. It was his last major contribution, and also his most general term (which could explain its relative lack of controversy and general acceptance).  In a review of the biome concept, Carpenter (1939) credited Clements with first proposing biome as synonymous with biotic community in 1916. Victor Shelford, Clements colleague and later co-author, used biome in a classification of communities (Shelford, 1932). It was, however, in Bio-ecology (Clements and Shelford, 1939) just six years before his death that Clements' developed fully his last major conceptual term. (Clements apparently was sole author of Chapter 2 of Bio-ecology and it was so confusing to reviewers that he volunteered to delete it; for unknown reasons Shelford, who was handling the publishing, did not remove Chapter 2 [Croker, 1991, p. 88-89].)

In Chapter 2 Clements did not abandon his famous (infamous according to detractors) metaphor or analogy of vegetation, the formation, as a complex organism (Clements, 1916a, p. 124). In Bio-ecology it was the biome that was " a social organism", "a complex organism", "or superorganism" (Clements and Shelford, 1939, p. 20, 21):

  "The concept of the biome is a logical outcome of the treatment of the plant community as a complex organism, or superorganism, with characteristic development and structure".     

In Plant Succession, his first monumental monograph, (Clements, 1916a, p. 116) cited Grisebach (1838, p. 160) as the introduction of the term formation. Eight pages later Clements (1916a, p. 124) cited himself as having " ... advanced the concept that the formation was essentially developmental in character, and stated that it may be regarded as a complex organism which shows both functions and structure ...". (Note how little the words changed from 1916 to 1939 except that inclusion of animals changed formation or climax to biome.)

Plant Succession did not include animals in the formation (though action of animals is replete throughout the monograph). Consistent with his usage quoted in Bio-ecology above, formation was vegetation in Plant Succession: "The unit of vegetation, the climax formation, is an organic entity". Inclusion of animals in the formation (= climax)  "in the biotic sense" was what distinguished biome from the former vegetation formation (the climax vegetation which was climatic climax, the monoclimax at regional scale) and expanded formation or climax to be exact synonyms of biome (above quote).
For the historical record, Carpenter (1939, p. 78) recorded that Clements first proposed biome in December, 1916 at a New York meeting of the Ecological Society of America. (Clements, 1916b) defined biome thusly:
“The biotic community is regarded as an organic unit comprising all the species of plants and animals at home in a particular habitat”.
In Carpenter’s discussion of this passage, which was Clements’ first use of biome, Carpenter (1939, p. 79) astutely observed:
  “It is noteworthy that the term is here used as synonymous with ‘biotic community’ and not in its present sense which has reference to the ‘biotic formation’”.
Yet, three sentences following the one cited above from Clements (1916b) and following Carpenter’s quoting of the entire passage in which “biotic formation” was used by Clements, Carpenter in that passage (1939, p. 79) ignored the fact that Clements called the biome both “biotic community” and “biotic formation” (within 19 words of each other). Clements had an uncanny ability to confuse the leading ecological minds of his day (including those of his closest friends) as well as those of the present. For his part, Carpenter (1939, p. 75) in the second sentence of his paper acknowledged both uses of biome in stating what is most likely the first formal definition of biome based on Clements introduction of the term in 1916:
  “The concept of the biome is dual, ie., first, biotic communities exist in nature, and second, the biome is the primary unit of bioecology possessing formational rank (sensu Clements)”.
Carpenter (1939, p. 75) then used a passage from Shelford and Olson (1935) as “a concise statement of the concept”:
  “The primary unit of bioecology is the biome, a community of formational rank in the largest sense of the term. The biome is characterized by uniformity of physiognomy of the plant climaxes and in a lesser way by the climax states. It is characterized by a combination of major and minor influent animals, a few climax influents, and many small influents and subinfluents. A certain grouping of species and varieties is characteristic of each biome. A biome or bioecological formation is based upon both plants and animals. Bioecology considers that plants and animals are inseparably united in the structure of any community”.  
As envisioned by Clements the biome was the biotic community only; biome did not include abiotic factors. This original view of the broadest unit of biotic community consisting solely of (limited to) plants and animals is still the almost universally accepted meaning of biome. This is the definition as used by the Society for Range Management, which is the most explicit in excluding abiotic factors:
  “a major biotic unit consisting of plant and animal communities having similarities in form and environmental conditions, but not including the abiotic portion of the environment" (Jacoby, 1989; Bedell, 1998). The last phrase was added to the  definition as it first appeared in the second edition of the SRM glossary (Kothmann, 1974); otherwise all definitions are identical.
Other definitions differ but slightly as indicated by some representative examples: 
  "a recognizable complex biotic community of a given region, produced by the interaction of climatic factors, living organisms, and substrate; especially a community that has developed to climax vegetation, such as tundra, coniferous forest or grassland" (Morris, 1992),
  “Regional climates interact with regional biota and substrate to produce large, easily recognizable community units, called biomes. The biome is the largest land community unit which it is convenient... The biome is identical with major 'plant formation', except that the biome is a total community unit and not a unit of vegetation alone" (Odum, 1971, p. 378),
  " ... climax formations of plants and animals considered together....; a large, primary biotic community in which the climax vegetation ... is more or less uniform..." (Polunin, ps. 211, 304)
  "... the largest and most comprehensive kind of plant community; the plants and animals in an ecosystem may be termed a biome..." (Spurr and Barnes, 1980, ps. 460, 461), 
  "largest recognizable subdivision of the terrestrial ecosystem, including total assemblage of plants and animals" (Bailey, 1996, p.165), and
  “a regional ecosystem with a distinct assemblage of vegetation, animals, microbes, and physical environment often reflecting a certain climate and soil” (Society of American Foresters [Helms, 1998]).
None of these definitions is descriptively complete (see end of Biome section), but they are consistent (nearly identical except for the last three that mention ecosystem) and convey the general concept and connotation. Only the last two are somewhat ambiguous implying that abiotic components of ecosystems could be included in the biome. The last definition was definitely greatly expanded from the original Clementsian conceptual view because the SAF clearly included physical and chemical components as well as biological ones which is a perspective adamantly rejected by Clements and Shelford in first presenting the term in full publication in Bio-ecology (1939, p. l3):
  “In passing, it may be pointed out that to include the habitat in the community obliterates the essential distinctions between the living and non-living, and carries synthesis to the extreme where its very purpose is defeated”.  


Biome:  A Biotic Community

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Biome, as coined and applied by Clements, was not the ecosystem and by definition could not be the ecosystem. This is self-evident. Otherwise biome would have been the term settled upon for the ecological unit of organization that came to become identified as the ecosystem.  Clearly the last two, the Bailey (1996) and Society of American Foresters (Helms, 1998), definitions of biome are a more comprehensive perspective and an incorrect interpretation, in direct contradiction, of the original meaning of biome. In using biome as a synonym for an ecosystem of regional scale Bailey (1996) and the SAF (Helms, 1998) negated what is unique about the biome concept. The biome (= biotic formation) is the regional plant-animal community, the “community of formational rank” (Carpenter, 1939), but it is not the regional-scale ecosystem. The latter view is the newly emergent concept of ecoregion described in the preceding section.

The units or terms forest region and grazing region are basically synonyms in Forestry and Range Management, respectively, for formation. “The forester’s term forest region is nearly equivalent to the ecologist’s formation” (Baker, 1950, p. 44). Westveld (1939) organized the chapters of his classic silvicultural text according to forest regions without bothering to define the term. His forest regions were smaller than the six forest regions identified by the U.S. Forest Service to include all forest vegetation of North America (Matoon, 1936; Toumey and Korstian, 1947, ps. 362-365). Stoddart and Smith (1943, 1955) used the term grazing region and designated several of these but, like Westveld, did not define the unit. They appeared to use grazing region as a synonym for vegetation region:

  “The term  vegetation region applies to broad geographical areas of vegetation, parts of which may be dominated by several different species. The vegetation regions are  large areas having comparable vegetation, climate, and range practices. Each may be composed of a number of grazing types (Stoddart and Smith, 1955, p. 46).
In turn:
  “The terms grazing type or vegetation type are not distinct in their usage. They generally refer to the species or various combinations of species which dominate or appear to dominate the range, thus giving it characteristic appearance” (Stoddart and Smith, 1955, p. 46).
As discussed in the next section, range vegetation (= cover= dominance) types more or less correspond to plant associations as traditionally defined/described by the Anglo-American view of vegetation. These associations comprise the major subdivisions of plant formations or biomes.
Sampson (1952, p. 100) followed this convention when for North American range vegetation he used associations as the major (broadest) vegetational units comprising formations that were based on dominant plant life form (eg. grassland, desert shrub, forest). For forest and scrub formations the units or headings of Sampson (1952) closely resembled those of Stoddart and Smith (1943, 1955). For grasslands Sampson (1952, p. 100) designated as associations what Stoddart and Smith (1955, ps. 46-61) labeled grazing regions (eg. tall-grass prairie association or region, short-grass plains association or region, Pacific bunchgrass association or bunch-grass region). Sampson (1952, ps. 14-39) used region as a more general term when discussing “pasture areas” of the various continents on broad scales.
Given the arrangement just described and the fact that grazing and forest regions were the largest, most general (broadest) units of range and forest vegetation as interpreted by what were historically the standard texts in Range Management and Forestry, it seemed obvious that “region” was the practical synonym or equivalent applied by rangemen and foresters to formation or, later, the synonymous biome.
In Chapter 2 of Bio-ecology Clements was emphatic that the biome was only the biotic community. Biome did not include habitat, the total of the various physical factors (or forces or conditions) in or on which the biome existed. Habitat "is used here solely in relation to physical and chemical factors". In further distinction, environment was "the total setting of individual or organism" (Clements and Shelford, 1939, p. 26). Biotic community and habitat were distinct but interacted. This was  "...the cause-and-effect interaction of habitat and community" (Clements and Shelford, 1939, p. 19). Specifically, " ...the community is acted upon by the habitat ..." (Clements and Shelford, 1939, p. 55), but " ... to include the habitat in the community obliterates the essential distinctions between the living and non-living, and carries synthesis to the extreme where its very purpose is defeated" (Clements and Shelford, 1939, p. 13).
It was in this uncompromising fundamental principle that Clements and his friend Arthur Tansley differed most substantively (far more than monoclimax vs. polyclimax, which is a fact apparently missed by most observers). Clements was also at odds with other prominent ecologists on this point, especially aquatic ecologists and limnologists "...who consider the lake as a whole to be an organic entity or organism". Many of those who worked with organisms in water were on the verge of reaching the inevitable endpoint of Tansley's ecosystem because "... it is more difficult to trace the application of the biotic concept in water than on land" (Clements and Shelford, 1939, p. 13).
On the other hand, there were numerous ecologists who viewed organisms and environment as interrelated yet also saw them as distinct. These workers looked for relations of cause-effect (biome was the result or product and climate, the cause) and action-reaction (environment acted on organisms and organisms reacted on the environment) (McIntosh, 1985, p. 194). Not exactly the ecosystem concept. Close? Yes, but not quite what Tansley (1935, p. 299) had in mind in his famous introduction of the ecosystem:
  "the whole system (in the sense of physics) including not only the organism-complex, but also the whole complex of physical factors forming what we call the environment of the biome- the habitat factors in the widest sense".
Biome. Tansley hit the touchstone in his landmark "use and abuse" paper, and four years before Clements went "whole-hog" with biome in Bio-ecology. But it was not the same concept, not quite. Again in Chapter 2 of Bio-ecology Clements praised "the theme of the complex or social organism" of John V. Phillips (1934-1935) describing it as the "'open sesame'" and "veritable magna carta for future progress" (Clements and Shelford, 1939, p. 24). Inside the same parentheses citing Phillips, Clements put "cf. Tansley, 1935". What did Clements mean when he wrote that “confer” and cited Tansley's introduction of the ecosystem and his harsh criticism of Clements' organicism? Did Clements mean that the reader should contrast Tansley's "ecosystem" with Clements' "complex organism"? Or did Clements mean that Tansley's  earlier "quasi-organism" and his recently introduced "ecosystem" were one and the same thing, and thus similar to the "complex organism"? Did Clements mean that the "ecosystem" was a partner in the "magna carta"?
In the introduction of his "use and abuse" paper Tansley wrote: "If some of my comments are blunt and provocative I am sure my old friend Dr. Clements and my younger friend Professor Phillips will forgive me" (Tansley, 1935, p. 285). Later in the last sentence of the paragraph in which he discussed organicist philosophy and "the holistic faith" and showed how they could be confusing in Ecology, Tansley (1935, p. 290) ended with: "...I believe (with Clements and Phillips) the idea to be of great service". There was common ground in this view of organisms and their environment, but there remained differences.

The latest version of Holism--Holistic Resource Management 
(A Historical Note)
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(Historical Note: Since the third edition of Glossary of Terms Used in Range Management [Jacoby,1989], the Society for Range Management has recognized Holistic Resource Management or Holistic Management. Holism has been a basic thought or philosophy underlying ecological theory, and thus natural resource professions like Range Management and Forestry, since the beginning.  This fact has emerged fairly recently as the histories of Ecology and related disciplines have been formalized and published to become widely available through university presses. Holism as a philosophy or philosophical theme was central to both the biome and ecosystem concepts. Holism or the holistic philosophy has often been simplified in abbreviated popular usage as: "The whole is greater than the sum of the parts" [see pages 23-24 of Bio-ecology.].  Several philosophers contributed to holism including  Auguste Comte and his  positivist philosophy, two other sociologists, Herbert Spencer and Lester Frank Ward, and philosopher Alfred North Whitehead with his organicism.  All of these were sources for Clements "complex organism" and climax that became the biome. More influential than any of them in later years was the South African statesman Jan Christian Smuts and his book, Holism and Evolution (1926). Smuts’ holism was apparently the major philosophical influence on John V. Phillips, the South African botanist/ecologist who had the most direct impact on Clements and Tansley at the time when Tansley (1935) criticized Clements and Phillips and rejected their superorganism to in turn develop his ecosystem concept. The intriguing trail of philosophy, sociology, romanticism, idealism, and metaphor that braided into the ecological theory of both Clements and Tansley can be pieced together from Tobey [1981], McIntosh [1985], and Golley [1993]. These histories are consistent in their conclusions, and their indexes are remarkably complete.  Details of organicism in the Clementsian paradigm are discussed below.)
Tansley introduced the ecosystem by juxtaposing it with biome:
  "I have already given my reasons for rejecting the terms 'complex organism' and 'biotic community'. Clements' earlier term 'biome' for the whole complex of organisms inhabiting a given region is unobjectionable, and for some purposes convenient. But the more fundamental conception is, as it seems to me, the whole system (in the sense of physics) ...[And then the definition of ecosystem quoted above.] [W]e cannot separate [organisms] from their special environment, with which they form one physical system".   
It would appear that biome could be defined or interpreted as the biotic part (the producer, consumer, reducer, manipulator components) of the ecosystem, if the ecosystem was large enough to accommodate this largest unit of a biotic community. This would seem to be the standard usage that was "worked out" in the years since this hard-fought but often touching battle of ideas and concepts among giants of Ecology. As with the debate between monoclimax and polyclimax this is, to a large extent, a difference in ecological scale. By definition the biome has to be large, specifically regional in scale (recall above definitions). In contrast ecosystem can be of any size and scale from global, the biosphere, to the most local (eg. a cow track).
Biome is consistent with the biotic community of the macroscale ecological region of Bailey (1996) mentioned above. Coincident usage of biome and ecosystem obviously would be compatible at regional or zonal scale where biome is the regional biotic community (bioregion is another synonym for biome). Probably the most revealing (certainly the largest) example of this was the International Biological Program (IBP).
The IBP was the international organization for ecological study and this was in the framework of ecosystems especially in the United States (Golly, 1993, p. 1, 75, 109-140, 184-185). IBP ecosystem study was under the umbrella of the biome. " Only one part of IBP, biome studies was focused on ecosystem studies" (Golly, 1993, p. 110). "The U.S. biome program dominated, and in many peoples minds characterized, the IBP" (Golly, 1993, p. 141). IBP became synonymous with biome studies in the thinking of some people (Golly, 1993, 112). In the USA there were five biome projects ranging from tundra through deciduous and coniferous forests to desert biomes, but as most appropriate for the Clementsian term the initial and, in most minds, major project was the Grassland Biome program (Golly, 1993, ps. 118, 119, 136, 141; McIntosh, 1985, p. 219).
The International Biological Program was— symbolically if not substantively— the crowning victory for the ecosystem and the biome concepts. It would seem that in the context of the long-running debate between emphasis on the biotic community vs. the "whole system" IBP ecologists compromised and adopted both models.  With emphasis on ecosystem studies it appeared initially that Tansley won in matters of real substance and Clements got a face-saving fig leaf. In reality, however, this organizational arrangement did not serve either model to best advantage. Placement of IBP programs that were intended to study "whole systems" of abiotic and biotic components "inside" a strictly biotic community (and the largest biotic unit at that) somewhat reduced effectiveness of both models. For one thing, this arrangement led some ecologists to confuse the "complex organism" of Clements with the ecosystem, the "whole system", of Tansley (Golly, 1993, ps. 34, 201). For another, the biome programs had marginal impact on the development of ecosystem theory (Golly, 1993, p. 139). Finally, the bioregional scale of biomes may have interfered with ecosystem analysis because ecologists did not study or even establish the spatial scale of the "larger system of which the ecosystem was a part" (Golly, 1993, p. 199). In spite of framing IBP ecosystem studies at the size of biomes such research did not advance Landscape Ecology (Golly, 1993, p. 117, 175).
McIntosh (1985, p. 118) noted that the connotation of biome as formation or climax was "tacitly ignored" when biome was widely accepted "as the basis for big ecosystem ecology in the 1960s" (the start-up of the IBP biome programs).The Ecology establishment refused to reject Clements (and an ecological unit as obvious as the biome) even though it of necessity accepted Tansley's ecosystem concept as the only option for studying interaction of organisms in their total environment. 
Acceptance of the biome by ecologists like those of the International Biological Program was likely a natural response or commonsense approach for organizing research on the "easily recognizable" or "largest recognizable" ecological units or levels in Nature that could be distinguished from each other.
The "recognizable" feature of the biome is the regional plant community, the formation (= climax vegetation, zonal vegetation, or macroscale vegetation). Formation was distinguished by the dominant life (or growth) form and thus the vegetational physiognomy. Thus the major formations of grasslands, shrublands like chaparral or desert, tundra, deciduous or coniferous forest, etc. became the biomes.
As specified at beginning of this section, none of the quoted definitions of biome were comprehensively complete. A full definition should specify that formation, hence biome, is distinguished by the dominant plant form or family (eg. Gramineae of grasslands) and physiognomy of the vegetation (Allen, 1998,  p. 374-375). The original definition of formation by Grisebach (1838)—the phytogeographical formation-- stipulated a group of plants having "a fixed physiognomic character" (quoted in Warming, 1909,  p.139). Warming (1909, p.140) defined formation "as a community of species, all belonging to definite growth-forms, which have become associated together by definite external *(edaphic or climatic) characters of the habitat to which they are adapted". He continued " ... a formation appears with a certain determined uniformity and physiognomy, even in different parts of the world, and even when the constituent species are very different and possibly belong to different genera or families" (Warming, 1909, p. 140). Braun-Blanquet (1932, p. 302) also specified the criteria of the same life-form and "uniform physiognomy and more or less uniform habitat requirements".
Warming (1909, p. 137-138) listed the following features of physiognomy: dominant growth-forms, density of vegetation (number of individuals), height of vegetation, color of vegetation, seasonal relationships (eg. evergreen vs. deciduousness), duration of life of species (life cycle, woody vs. herbaceous parts, and persistence of aboveground parts), and number of species.    
These criteria are "easily recognizable" and distinguish vegetation at the broadest, most general categories. These in turn support similar animal life and reflect both climate, regional landforms, and the more general taxa of soils such that the biome is a most useful community unit. This is attested to by the continuing organization of texts and references according to biomes or similar units (eg. Vankat, 1979; Barbour et al., 1999). In his introductory textbook, Ecology of North America, Bolen (1998, p. xiii) remarked that his title mimicked Shelford’s monographic coverage and, while differing "fundamentally" from it, was organized on the basis of biomes and communities therein.
The continuing use and usefulness of the biome attest to the genius and immortality of Frederic E. Clements. Likewise, the relatively recent development of Landscape Ecology and its entry into general land management and the concept of a spatial hierarchy of ecosystems (ecological units, ecosystem classification) return Range Management and Forestry full circle to the regional scope or macroscale of the original Clementsian (monoclimax) perspective. This is the system ingeniously formalized as Ecosystem Geography by R.G. Bailey (1996, 1998) and introduced above in context of climax theories. The largest spatial scale, most general, ecosystems are those designated macroecosystem or ecoregion (= ecological region) which are based on macroclimates, ecoclimatic zones, determined by latitude and continental position (Bailey, 1996, ps. 51-104; Bailey, 1998, ps. 6-9, 33-50). The macroscale ecosystems (= ecoregions) correspond to the biome (Bailey, 1996, ps. 52, 157, 165; Bailey, 1998, p.39), specifically to the biotic community or biotic formation of ecoregion scale. The ecoregion is the climatic climax (= regional climax = monoclimax) in slightly different and newer terms. Subdivision of ecoregions into mesoscale ecosystems (mesoecosystems) based on landform differentiation and these into microscale ecosystems (microecosystems) as to edaphic-topographic differentiation is the contemporary blending of Tansley polyclimax into the larger-scale Clementsian monoclimax (regional or climatic climax), the biome. The biome persist renamed ecoregion to more obviously acknowledge the determining role of regional-scale abiotic variables, especially climate (ie. biome= the combined plant and animal community of the ecoregion). Ecoregion corresponds to the climatic— the regional or zonal— climax. The microecosystems, the smallest or local ecosystems, “are the homogeneous sites commonly recognized by foresters and range scientists” (Bailey, 1996, p. 23).
The biome concept has continued to remain of great practical use and to be applied in ways especially useful in agricultural and natural resource professions like Range Management, Forestry, Wildlife Management, and Fisheries. In this author's opinion, one of the best examples of this reality is to be found in Biomes of Earth (Woodlard, 2003) that covered such range biomes as temperate grasslands, tropical savannas, deserts, tundra, Mediterranean woodland and scrubland, temperate deciduous forests, and boreal forests. Likewise, extremely useful for basic instruction were the different titles in the series Biomes of the Earth including Grasslands, Deserts, Temperate Forests, and Tropical Forests by Allaby (2006, 2006, 2006, 2006), Tundra and Wetlands (Moore, 2006) and Taiga (Day, 2006). Clements' visionary view of the biotic community remains as useful as ever even if it is not as fashionable as it once was.
The cliché cited in the Range Site section is again appropriate: “What goes around, comes around.” Obviously and beyond any question, any debate,  Ecology as applied to Range Management and Forestry in North America remains at its foundation and core Clementsian as annealed with such basic concepts of Tansley as polyclimax and ecosystem. Applying the imagery of Clements’ “dynamics of vegetation”, ecological concepts cycle.

In the context of contemporary holistic theories of evolutionary change in plant communities Barbour et al. (1999, p. 208) concluded with the following observation:

  "It is ironic that such recent models bring us back full circle to Clementsian ideas of the community as some kind of superorganism-ideas that stimulated the very beginnings of American plant ecology. The more things change, the more they stay the same".
"The biome or plant-animal formation is the basic community unit, that is, two separate communities, plant and animal, do not exist in the same area. The sum of plants in the biome has been known as vegetation, but for r animals no similar distinctive term has become current. It is obvvious, however,that the two do notr represent natural divisions of the biotic complex ...

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