6. E. L. Thorndike, Animal Intelligence (Mac- 16. 3. Kaas, W. C. Hall, I. T. Diamond, "Dual millan, New York, Neurol. 91, 441 (1949); -, in Biological 1911). representation of the retina in the cortex of and Biochemical Bases of Behavior, H. F. 7. E. D. Adrian, The Physical Background of the hedgehog in relation to architectonic Harlow and C. N. Perception (Oxford Univ. Press, London, Woolsey, Eds. (Univ. of boundaries and thalamic projections," in prep- Wisconsin Press, Madison, 1958); L. T. Dia- 1947). aration. mond, K. L. Chow, W. D. Neff, J. Comp. 8. D. H. Raab and H. W. Ades, Amer. J. 17. R. A. Lende and K. M. Sadler, Brain Res. Neurol. 109, 349 (1958). Psychol. 59, 59 (1946); M. R. Rosenzweig, 5, 390 (1967). 29. L. J. Garey and T. P. S. Powell, Proc. Roy. ibid., p. 127; R. A. Butler, I. T. Diamond, 18. P. Abplanalp and W. Nauta, personal com- Soc. London Ser. B 169, 107 (1967); M. W. D. Neff, J. Neurophysiol. 20, 108 (1957); munication. Glickstein, R. A. King, J. Miller, M. Berkley, R. F. Thompson, ibid. 23, 321 (1960). 19. J. Altman and M. B. Carpenter, J. Comp. J. 9. W. D. Neff and I. T. Comp. Neurol. 130, 55 (1967). Diamond, in Biological Neurol. 116, 157 (1961); D. K. Morest, Anat. 30. The abbreviations are and Biochemical Bases of Behavior, H. F. following used in the Record 151, 390 (1965); E. C. Tarlov and figures and figure legends: A, auditory area of Harlow and C. N. Woolsey, Eds. (Univ. of R. Y. Moore, J. Comp. Neurol. 126, 403 cortex; CM + Pf, centromedian + parafas- Wisconsin Press, Madison, 1958); R. B. Mas- (1966). cicular nuclei; GL, lateral geniculate nucleus; terton and I. T. Diamond, J. Neurophysiol. 20. H. S. Gasser and J. Erlanger, Amer. J. Physiol. GM, medial geniculate nucleus; habe- 27, 15 (1964). 88, 581 Hab, 10. (1929). nula; Hip, hippocampus; L, lateral group of 1. M. Warren, Ann. Rev. Psychol. 16, 95 21. G. H. Bishop, J. Nervous Mental Disease 128, nuclei; LP, lateroposterior nucleus; MD, medi- (1965). 89 (1959). odorsal nucleus; PC, posterior commissure; 11. K. S. Lashley, in Symposia of the Society for 22. C. J. Herrick, Brains of Rats and Men (Univ. Experimental Biology (Academic Press, New Po, posterior nucleus; Pul, pulvinar nucleus; of Chicago Press, Chicago, 1926). R, reticular nucleus; S I, somatic area I; York, 1950), vol. 4. 23. R. P. Erickson, W. C. Hall, J. A. Jane, M. S 12. II, somatic area II; SC, superior colliculus; K. Z. Lorenz, ibid., vol. 4. Snyder, I. T. Diamond, J. Comp. Neurol. 131, area of 13. G. Elliot Smith, T, temporal cortex; TO, optic tract; The Evolution of Man (Ox- 103 (1967). ventral V visual area V ford Univ. Press, London, 1924); V, group; I, I; II, C. J. Her- 24. J. E. Rose and C. N. Woolsey, Electroen- visual area II; VGL, ventral lateral geniculate; rick, Brain of the Tiger Salamander (Univ. cephalog. Clin. Neurophysiol. 1, 391 (1949). VL, ventrolateral nucleus; VM, ventromedial of Chicago Press, Chicago, 1948). 25. Unpublished experiments in our laboratory. nucleus; VP, ventroposterior nucleus; ZI, 14. G. G. Simpson, Bull. Amer. Museum Nat. 26. M. Snyder, W. C. Hall, I. T. Diamond, Psy- zona incerta. Hist. 85, 1307 (1945); A. S. Romer, Vertebrate chonomic Sci. 6, 243 (1966); M. Snyder and 31. The research described was supported by grant Paleontology (Univ. of Chicago Press, Chi- I. T. Diamond, Brain Behavior Evolution 1, MH-04849 from the National cago, 1945); J. Z. Young, The Life of Ver- Institute of 244 (1968). Mental Health. For their helpful comments we tebrates (Oxford Univ. Press, London, 1962). 27. H. Killackey, I. T. Diamond, W. C. Hall, G. thank Doctors G. Bishop, J. Kaas, G. Kimble, 15. W. C. Hall and I. T. Diamond, Brain, Be. Hudgins, Federation Proc. 27, 517 (1968). N. Guttman, J. Jane, R. B. Masterton, and havior Evolution 1, 181 (1968). 28. J. E. Rose and C. N. Woolsey, J. Comp. M. Warren. at the ecosystem level as a means of emphasizing those aspects of ecological succession that can be accepted on the on March 3, 2011 basis of present knowledge, those that require more study, and those that have The Strategy of special relevance to human ecology. Ecosystem Development Definition of Succession Ecological succession may be defined An understanding of ecological succession provides www.sciencemag.org in terms of the following three param- a basis for resolving man's conflict with nature. eters (1). (i) It is an orderly process of community development that is rea- sonably directional and, therefore, pre- Eugene P. Odum dictable. (ii) It results from modifica- tion of the physical environment by the community; that is, succession is com- munity-controlled even though the phys- Downloaded from The principles of ecological succes- gists to regard "succession" as a single ical environment determines the pattern, sion bear importantly on the relation- straightforward idea; in actual fact, it the rate of change, and often sets limits ships between man and nature. The entails an interacting complex of proc- as to how far development can go. (iii) framework of successional theory needs esses, some of which counteract one It culminates in a stabilized ecosystem to be examined as a basis for resolving another. in which maximum biomass (or high man's present environmental crisis. Most As viewed here, ecological succession information content) and symbiotic ideas pertaining to the development of involves the development of ecosystems; function between organisms are main- ecological systems are based on descrip- it has many parallels in the develop- tained per unit of available energy flow. tive data obtained by observing changes mental biology of organisms, and also In a word, the "strategy" of succession in biotic communities over long periods, in the development of human society. as a short-term process is basically the or on highly theoretical assumptions; The ecosystem, or ecological system, is same as the "strategy" of long-term very few of the generally accepted hy- considered to be a unit of biological evolutionary development of the bio- potheses have been tested experimental- organization made up of all of the or- sphere-namely, increased control of, ly. Some of the confusion, vagueness, ganisms in a given area (that is, "com- or homeostasis with, the physical en- and lack of experimental work in this munity") interacting with the physical vironment in the sense of achieving area stems from the tendency of ecolo- environment so that a flow of energy maximum protection from its pertur- The author is director of the Institute of Ecol- leads to characteristic trophic structure bations. As I illustrate below, the strat- ogy, and Alumni Foundation Professor, at the and material cycles within the system. egy of "maximum protection" (that is, University of Georgia, Athens. This article is based on a presidential address presented before It is the purpose of this article to sum- trying to achieve maximum support of the annual meeting of the Ecological Society of marize, in the form of a tabular model, complex biomass structure) often con- America at the University of Maryland, August 1966. components and stages of development flicts with man's goal of "maximum 262 SCIENCE, VOL. 164 production" (trying to obtain the high- ter and biomass (B) will accumulate in early seasonal bloom characterized by est possible yield). Recognition of the the system (Table 1, item 6), with the rapid growth of a few dominant species ecological basis for this conflict is, I result that ratio P/B will tend to de- being followed by the development later believe, a first step in establishing crease or, conversely, the BIP, BIR, or in the season of high B/P ratios, in- rational land-use policies. BIE ratios (where E = P + R) will creased diversity, and a relatively steady, The earlier descriptive studies of suc- increase (Table 1, items 2 and 3). Theo- if temporary, state in terms of P and R cession on sand dunes, grasslands, for- retically, then, the amount of standing- (4). Open systems may not experience ests, marine shores, or other sites, and crop biomass supported by the available a decline, at maturity, in total or gross more recent functional considerations, energy flow (E) increases to a maximum productivity, as the space-limited micro- have led to the basic theory contained in in the mature or climax stages (Table 1, cosms do, but the general pattern of bio- the definition given above. H. T. Odum item 3). As a consequence, the net energetic change in the latter seems to and Pinkerton (2), building on Lotka's community production, or yield, in an mimic nature quite well. (3) "law of maximum energy in bio- annual cycle is large in young nature These trends are not, as might at first logical systems," were the first to point and small or zero in mature nature seem to be the case, contrary to the out that succession involves a funda- (Table 1, item 4). classical limnological teaching which mental shift in energy flows as increas- describes lakes as progressing in time ing energy is relegated to maintenance. from the less productive (oligotrophic) Margalef (4) has recently documented Comparison of Succession in a to the more productive (eutrophic) this bioenergetic basis for succession and Laboratory Microcosm and a Forest state. Table 1, as already emphasized, has extended the concept. refers to changes which are brought Changes that occur in major structur- One can readily observe bioenergetic about by biological processes within the al and functional characteristics of a changes by initiating succession in ex- ecosystem in question.