Textbook Misconceptions: The Climax Concept of Succession David J. Gibson SUCCESSION iS the processand patternof changes Gleason (1917, 1926) criticized Clements' monocli- following a disturbancein communities through max theory because it lacked accommodationof indi- time at a site. It is an important concept in an vidual plant population behaviors (see also Peet & understanding of ecological dynamics; this definition Christensen 1980). Tansley (1935)proposed the poly- incorporatesWhite & Pickett's (1985) view of distur- climax theory, in which a climax community exists bance as any relatively discrete event in time that but consists of a mosaic controlled by local soil disrupts ecosystem, community or population struc- moisture, nutrients, parent material, topography, Downloaded from http://online.ucpress.edu/abt/article-pdf/58/3/135/47535/4450101.pdf by guest on 30 September 2021 ture. As a teaching tool, succession allows students to slope exposure, fire, and animal activity. Despite understand the changing nature of communities, as these concerns, the concept became the central tenet well as conceptualize the result of species' interac- of range condition analysis used by the USDA for tions. range management (Dyksterhuis 1949) and is still Since Clements' seminal paper (1916), the idea of a used today even though it is recognized as concep- deterministic end point to the process, called the tually flawed (oyce 1993;Tausch et al. 1993). climaxstage, has become entrenched in the literature. Whittaker (1953) proposed the climax-patternhy- This view was challenged in the 1950s and is now pothesis as a modification of the polyclimax view- regarded as extreme (Simberloff1982). Despite mod- point. The climax-patternhypothesis combines com- ern views of the process of succession (McCook munity and environmental gradients to yield a 1994), and a rejection of the Clementsian climax variety of climax stands in an area that forms part of thesis, currentintroductory ecology and environmen- a continuous mosaic. Succession proceeds toward tal science college textbooks retain outdated and one of an infinite number of alternative climax com- simplistic views of succession. In this articleI review munities, each in equilibrium with its own, unique the development of the climax concept of succession, site as a function of the success of populations of illustrate the misconceptions in current textbooks, species in relation to local environmental gradients. and provide a conceptual model for an updated view Nevertheless, even with this pluralistic view of the of succession useful in teaching at the introductory process, the climaxwas recognizedas a partiallystabi- level. lized steady-state community that was deterministic within the bounds of local environmentalgradients. Development of the ClimaxConcept of Like HarryHoudini's wager of money for scientific Succession evidence of spiritualism, the ecologist Frank Egler offered a $10,000 challenge to the scientific commu- Cowles (1899)and several Europeans(see review in nity to present evidence in support of the plant Whittaker 1953) developed the early ideas on the succession-to-climax viewpoint (Egler 1977). Al- nature of community change through time. These though this challenge was made for several years, the ideas were codified into a theoretical frameworkby money was never paid out. Clements in 1916. Clements proposed that succes- sional sequences were climaticallydetermined lead- More recently, ecologists have sought a mechanis- ing to a single self-perpetuating climax community; tic rather than pathway-oriented understanding of i.e. the monoclimax. Each climax community was succession (Pickettet al. 1987a).Various models have viewed as similarto an organism that grows, matures been proposed such as population-basedapproaches and dies. Although immediately challenged (Gleason (Peet & Christensen 1980; Finegan 1984), e.g. the 1917; Tansley 1935), this view became embodied in Vital Attributes model (Noble & Slayer 1980); the the literature. facilitation,inhibition and tolerance models (Connell & Slayer 1977);Grime's C-S-Rhypothesis (1979);and Tilman's (1985)resource-ratio hypothesis. Space pre- David J. Gibson, Ph.D.,is Associate Professorof PlantBiology at cludes a description of each of these here, but a Southern Illinois Universityat Carbondale, Carbondale, IL 62901-6509. discussion can be found in some science major text- books (see below) or in the original papers. TEXTBOOKMISCONCEPTIONS 135 Table 1. Textbooks evaluated for their coverage of the climax concept of succession. Nonscience Major Texts BSCS. (1992). Biologicalscience: An ecologicalapproach, 6th ed. Dubuque, IA: Kendall/HuntPublishing. Chiras, D.D. (1993). Environmentalscience: Action for a sustainablefuture, 4th ed. Redwood City, CA: Benjamin/Cummings Publishing Company. Cunningham, W.P. & Saigo, B.W. (1995). Environmentalscience: A globalconcern, 3rd ed. Dubuque, IA: Wm. C. Brown Publishers. Enger, E.D. & Smith, B.F. (1992). Environmentalscience: A studyof interrelationships,5th ed. Dubuque, IA: Wm. C. Brown Publishers. Kupchella, C.E. & Hyland, M.C. (1993). Environmentalscience: Living within the systemof nature,3rd ed. Englewood Cliffs, NJ: Prentice Hall. Miller, G.T. (1996). Livingin the environment:Principles, Connections and Solutions,9th ed. Belmont, CA: Wadsworth Publishing Company. Morgan, M.C., Moran, J.M. & Wiersma,J.H. (1993). Environmentalscience: Managing biological & physicalresources. Dubuque, IA: Wm. C. Brown Publishers. Nebel, B.J. & Wright, R.T. (1993). Environmentalscience: The way the worldworks, 4th ed. Englewood Cliffs, NJ: Prentice Hall. Downloaded from http://online.ucpress.edu/abt/article-pdf/58/3/135/47535/4450101.pdf by guest on 30 September 2021 Science Major Texts Begon, M., Harper, J.L. & Townsend, C.R. (1990). Ecology:Individuals, populations and communities,2nd ed. Sunderland, MA: Sinauer Associates. Brewer, R. (1994). Thescience of ecology,2nd ed. Philadelphia,PA: Saunders College Publishing. Colinvaux, P. (1993). Ecology2. New York:Chapman & Hall. Krebs, C.J. (1994). Ecology:The experimental analysis of distributionand abundance,4th ed. New York, NY: Harper/Collins. Odum, E.P. (1971). Fundamentalsof ecology.Philadelphia: W.B. Saunders Company. Smith, R.L. (1996). Ecologyand field biology,5th ed. New York:Harper & Row. Stiling, P. (1992). Introductoryecology. Englewood Cliffs, NJ: PrenticeHall. Modern perspectives of succession are presented physical scale, say the eastern U.S., it is entirely by Pickett and McDonnell (1989), Glenn-Lewin et al. reasonable to suggest that successional pathways (1992) and McCook (1994). Pickett and McDonnell will likely produce the equivalent of a climatically- (1989) contend that the successional climax is an controlled climax vegetation recognizableas the east- 'ideal' and an abstractionof reality. Reasons for this ern deciduous forest biome; deserts and grasslands include: are unlikely to occur there without large-scaleclimatic shifts. However, as the spatial scale of resolution 1. There is never an absence of disturbance. decreases, the certainty of predicting the eventual 2. Some communities are not in equilibriumwith outcome of succession decreases as does the self- the present climate. maintaining nature of these later stages. Thus, the 3. For some vegetation types a recurrent natural climax concept becomes untenable as site factors and disturbance (e.g. fire in tallgrass prairie) main- recurrent disturbance become more important at tains the community in what Clements would scales below that of the biome. Typically, the teach- call a pre-climaxcondition. ing of succession operates at the smaller scales, e.g. 4. The length of time necessary for some species to the oft-cited, but erroneous old-field succession from dominate a site is less than the return time of an annual weedy stage to so-called climax forest. disturbance. For example, McCune and Allen (1985)had difficulty Misconceptions in Modem Textbooks applying the climax concept to old-growth forests in Montana and suggested caution in using the concept. Texts used in teaching college environmental sci- Lertzman(1992) described subalpine hemlock forests ence and ecology were examined for their views on near Vancouver, Canada, that had not reached equi- the climax theory of succession (Table 1). Texts were libriumdespite being undisturbed for more than 1500 separated according to their intended use for non- years. Indeed, Miles (1987) pointed out that the idea science major courses (n = 8), versus science major of a successional climax is now out of favor. Pickett courses (n = 7). and McDonnell (1989)go furtherand suggest that the term climax should be avoided to prevent acceptance Nonscience Major Texts of the incorrectassumptions of classical theory. Textbooks intended for nonscience major courses As pointed out by Allen and Hoekstra (1992), in environmental science or ecology generally over- perhaps the main problem in adequately defining simplified the current view of succession. Worst of ecological concepts is one of scale. At the largest all, they perpetuated the outdated climax viewpoint. 136 THEAMERICAN BIOLOGY TEACHER, VOLUME 58, NO. 3, MARCH1996 The eventual, and inevitable, state was the climax the history of the development of successional the- community: ory. Successionwill proceeduntil a balancedstate betweenall Despite the more current approach of the science speciesand theirenvironment is reached.The final state is major texts, they differed in their treatments of the referredto