most notably followed in the United Land Management Policy States by Clements (1916), who with and Development of Ecological Concepts1 Weaver (Weaver and Clements, 1938) developed a strong school of successional based largely DONALD A. JAMESON on observations in the sandhills Associate Professor of Range Science, of Nebraska. Clementsian ecology College of Forestry and Natural Resources, became the focal point of U. S. ecol- Colorado State University, Fort Collins. ogy for many years, and certainly received much impetus from the Highlight facing range managers today into very practical management needs the categories of (1) scientific un- As ecological concepts become incor- that were pointed out during the porated into the training and back- derstanding of the , (2) “dust bowl” days of the 1930’s. ground informat,ion of professional technological efficiencies (as op- Clementsian ecology, and other land managers, they also become in- posed to technological possibilities), viewpoints of successional ecology, corporated into land management and (3) rural social adjustments. policies. Recent developments in ecol- propounds that we first begin with This order is not intended to assign ogy, such as nutrient cycling studies bare rock which is converted by and computer simulation of complex any priorities to these three tasks; stages. These stages may include processes, have a favorable climate for all are deserving of full considera- and , annual plants, acceptance. Possible applicatcions tion. This paper, however, will deal perennial forbs, grasses, and finally, should be carefully studied by land only with scientific understanding managers. in appropriate climates, shrubs or of the resource. . Such a progression is known Theories are basic tools of science; as a xerosere. On the other hand, It is certainly paradoxical that in all scientists need theories on which hydroseres, beginning with water a world filled with hunger, the and with which to operate. It mat- but ending with the same climax United States is constantly faced ters little whether the theory is cor- condition, also can occur. If the with the need to hold back on agri- rect, it must, however, be useful. progression from rock or water to cultural production. It is also dis- Consider, for example, earlier theo- the climax is set back turbing to many of us who have ries of electron flow. Much elec- by any , and progres- worked for years to increase live- tronic equipment was first designed sion is then allowed to resume, the stock production on rangelands that with the belief that electrons flow resumption of succession is known our efforts in this direction, al- in a certain direction around a cir- as secondary succession. though desirable from an individ- cuit. As it turns out, electrons actu- Most land managers in the United ual viewpoint, are no longer critical ally flow in exactly the opposite di- States today who are in a position from the national viewpoint. It is rection; nevertheless, circuits based to make policy decisions were most particularly frustrating because we on the original theory do work. likely trained in successional ecol- have the technology to double or Many other examples of operable, ogy. In fact, concepts of succes- perhaps triple the production from but inaccurate, theories exist. A sional ecology have been written our rangelands. Because of these theory, therefore, is to be judged into policy statements of many land facts, range managers have, in many not on the basis of truth, but on management and advisory agencies. cases, lost their sense of mission. the basis of its usefulness. As long In some agencies, Clementsian ecol- There are, however, more and as the theory is useful, it very likely ogy has become so entrenched in perhaps greater things which need will not be replaced, but when the service policy that any one speak- doing. I like to classify the jobs theory is no longer useful, it will ing out against these concepts, or eventually be replaced. The em- even offering additional concepts, lWork presented in this paper was phasis in this paper, for example, is considered a heretic. supported in part by National Science Foundation Grant GB-7824 for the is intended to be provocation rather Theories of successional ecology Analysis of Structure and Function of than accuracy, and hopefully the certainly have been useful. It was, Grassland . Many of the paper will have a short life. for example, a most useful and ideas expressed in this paper are the necessary tool to recover from some result of discussions with several of Ecological Concepts of the investigators in the Grassland of the earlier abuses in range man- Biome subprogram of the Interna- Existing Policies agement in the western United tional Biological Program, particu- Some early theories of ecology States. Certainly in many areas we larly L. J. Bledsoe and G. M. Van Dyne. Received January 23, 1970; ac- were developed from observations have a long way to go before we cepted for publication May 8, 1970. on the peat bogs of Europe, where can completely exhaust the benefits 2The author is Director of the Pawnee several observers felt that the bogs from successional ecology and its Site project in the Grassland Biome developed through well defined concepts. We have, however, con- program of the U.S. International Biological Program. stages. This reasoning was perhaps tinued to use successional ecology 316 POLICY AND ECOLOGY 317

over and over until it has lost much ray of concepts and mathematical the and predict many of its usefulness. Much of the west- techniques and approaches collec- results without actually doing field ern range is in a condition where tively known as . experiments. great progress from secondary suc- Since the term is used to describe a If we think about the few simple cession alone cannot be expected. potpourri of the interesting and compartments outlined above (pro- Most ranges are in much better uninteresting, valid and invalid, ducers, consumers, and decompos- condition than they were earlier, and meaningful and meaningless, ers), we see that we could readily and we certainly have the necessary it would be impossible to cover sys- subdivide these compartments into basic technology, if not the eco- tems ecology in a brief presenta- growth forms, species, individuals, nomic efficiency and political abil- tion. It is, however, possible to out- or parts of individuals. We could ity, to finish this particular job. In line what seems a dominant concept also consider many kinds of matter. addition, Clementsian “sand hill” as indicated by current interest of Thus our concept of the has been pressed into use the scientific community, the prob- could very readily become entirely in areas where it was not conceived ability of significant contributions too complex to handle by ordinary and where it is not quite so ap- of basic knowledge, and the validity bookkeeping systems. In addition, propriate. Perhaps a few examples of the use of the term systems the measurements of transfers from would be in order. In timbered ecology. one compartment to the other are lands, for instance, the progression Tansley ( 1935) introduced the in many cases quite difficult, and towards climax does not necessarily term “ecosystem” into the English in Lindeman’s time may have been equal a progression towards better language literature. Tansley’s in- impossible. In fact, many of them conditions for range livestock. In troduction of the term, however, are still impossible, but introduc- fact, a climax coniferous forest is was mostly a definition and it re- tion of radioisotopes as tracers and usually in very poor “range condi- mained for Lindeman (1942) to many sophisticated instruments tion.” On the other hand, a well clearly outline trophic (i.e., feeding have greatly facilitated and pro- established and well managed level) ecology which has, in recent moted studies of transfer processes. seeded range, by definition, is in a years, become a central theme for For these very pragmatic reasons, disclimax state because all of the much ecological research. Linde- therefore, trophic-dynamic ecology species present are invaders, but, man happened to be an aquatic did not immediately arise to the from the standpoint, ecologist, and his paper on the forefront after Lindeman’s original it may be excellent. trophic-dynamic aspects of ecology exposition. In fact, most of those Although theories of successional uses examples from aquatic com- attending universities over 20 years ecology are still used by land man- munities. Nevertheless, the prin- ago probably did not hear of agement agencies, many range re- ciples he outlined apply generally trophic-dynamic ecology. searchers have long since aban- to other ecological systems. doned this concept as a fruitful Lindeman said that an ecosystem Modelling and Ecosystems area of research. They have, in- is a system made up of various com- As noted above, when we subdi- stead, turned to such fields as plant partments; the compartments are vide the ecosystem compartments physiology, animal nutrition, and called trophic (feeding) levels and into the necessary functional com- agronomy (including reseeding and ordinarily include producers (or, plexity, the job of keeping track of brush control). This shift to simi- more commonly, green plants), con- the energy and matter flow among lar, but more restricted, fields has, sumers (which in turn can be sub- the various compartments soon be- in part, been promoted by educa- divided into primary consumers comes a major mathematical prob- tional institutions which have been which eat plants, secondary con- lem. Even for situations where the unable to offer solid training in sumers which eat primary consum- basic mathematical techniques are range science as a total system con- ers, etc.), and (which available very large problems could cept. This search for meaningful convert dead plant and animal not adequately be handled until research fields has led, in many matter back into carbon dioxide). computers came into common use. cases, to fragmented research pro- Energy is received from the sun, At first computers were slow, large, grams without a central theme, and and energy and matter are trans- and expensive to operate. As com- has occasionally produced dichoto- ferred among the various compart- puters have become larger in ca- mies between researchers and land ments. If we truly understood this pacity, they have also become gen- managers. transfer of energy and matter, we erally smaller in size, faster in would then truly understand the operation and, most important, Recent Trends in Ecology operation of the system. If we un- much cheaper per job. Use of more Useful as successional ecology has derstood these transfers so well that complex techniques has become been, it has become somewhat shop we could express them mathemati- more and more feasible. More worn and is now being replaced on cally, we could then examine the mathematicians, engineers, and now the theoretical front by a wide ar- effects of many manipulations of even biologists are becoming famil- 318 JAMESON iar with computer techniques. The development of mathematical tools used in analysis of feedback control systems is especially useful, and it it from this field particularly that much of the terminology of systems ecology is being drawn. An “adap- from tive control system with stochastic (time t ) inputs” (Rosen, 1967), for example, sounds exactly like an ecological Cl Live plonts situation. The concept of an adap- tive system, in fact, provides for C, Standing dead union of the theories of successional C, Plant litter ecology with the theories of trophic ecology if we consider an ecological C, M icrof lora system which is undergoing succes- C, Soil Organic Matter sion as a self-organized system C, (Margalef, 1968). We now find arising today a con- C, siderable number of mathemati- C, cally-oriented biologists, and bio- logically-oriented mathematicians C, Soil fauna and engineers, who are attacking C,, Animal litter the problem of trophic-dynamic ecology. It is something of a basic FIG. 1. A matrix of transfers between compartments of closed system. Here, 0 = no ground swell among ecologists. In transfers, -1 = diagonal elements, and + = transfer between compartments. The sum of all positive numbers in the columns of this figure will be +l, so that for closed fact, we can say with certainty that systems at steady state the total transfer to each compartment will sum to zero. complex ecological systems will be investigated from the standpoint of trophic-dynamic ecology and sys- pool of scientific manpower avail- of various transfers will make the tems engineering. The only ques- able at the several major nearby case that, in the strictest sense, there tion, since science does progress as universities and colleges and associ- are very few zero transfers. At this a body, is who is going to do it best. ated federal research organizations, point, however, the matrix is most It happens that at the moment and (iv) the obvious dependence of important to point out an ap- the primary worldwide research ef- man on the grasslands of the world. proach. fort in this area is centered about Ingestion of herbage by herbi- Matrix Representation of Ecosystems the International Biological Pro- vores is one transfer process-in gram (IBP). Particularly in the We have stated above that an eco- this case the transfer between live U. S. these efforts are imbedded in system is a system which transfers plants and a particular the integrated IBP research pro- energy and matter from one com- species. The rate of this transfer gram on the Analysis of Ecosystems partment to another (for a further process becomes an element in our (AOE). A number of IBP Biome discussion see Margalef, 1968). If who-eats-whom matrix. Biologists programs have been organized we have “n” such compartments, have been working on the deter- within the AOE including the we can describe a greatly simplified mination of many of these transfers Grassland, , Eastern Decidu- ecosystem as a “n x n,” who-eats- for some time, but others have not ous Forest, Western Coniferous whom matrix in which the ele- received a great deal of attention. Forest, Tundra, and Tropical ments of the matrix describe the In fact most of the energy and mat- Biomes. Of these biome programs, rate of transfer of energy or matter ter transfers cannot be measured the Grassland was selected for the from each compartment at time “t” directly. Therefore if we are to say first major effort because of (i) its to each of the compartments at that we understand an ecosystem by seeming simplicity, (ii) the location time “t + At” (Fig. 1). If we knew knowing where energy and matter of a suitable intensive study area, the individual coefficients or math- flows in the system, we must find namely the combined areas of the ematical functions for all such some other procedure. Pawnee National Grassland and transfers in this matrix, we could the Central Plains Experimental then claim to understand the func- An Analytical Approach Range, known in IBP circles as the tion of the ecosystem. In Fig. 1, I An alternative is to determine Pawnee Site, (iii) the rapid and ex- have entered some zero coefficients, the amount of energy and matter tensive cooperation of a suitable but scientists involved in the study in each compartment at several POLICY AND ECOLOGY 319 points in time. With these data Open Systems tern when forced or perturbated points in hand, we can arrive at a We can consider two forms with a known input, we are able to solution of the “n x n” matrix of of constant coefficient models-a determine the transfer function of coefficients which describes the flow “closed” form and an “open” form. the system, which is the ratio of the of the matrix using solution tech- These mathematical properties also output to the input. Once we de- niques as outlined by Berman et al. have important relationships to bio- termine the transfer functions of (1962a and 1962b) and Bledsoe and logical problems. A system can be the system, we can build a system Van Dyne (1968). considered “closed” if we can actu- simulator and replace these stan- To facilitate solution we can uti- ally measure all compartments. If dardized inputs with the variable lize any knowledge we have con- we are unable to measure the forcing functions which occur in cerning transfers, that is, we can amount of matter or energy in any nature, and observe the system be- provide constraints for the elements of the compartments, the system is havior under these conditions. Such of the matrix. For the most part “open” and we will not be able to concepts have been widely and we may guess the zero or near zero obtain a direct solution from the profitably used in some fields of coefficients from past experience. method presented above; therefore biology (Milsum, 1966) but have These analyses give us our first ap- we must have a measure of all not been commonly used in ecology. proximation which is a linear, con- transfers to and from compartments In rangeland ecosystems highly stant-coefficient model. Additional which we cannot measure directly. probabilistic rainfall is the chief information is required to develop In other words, we must measure perturbation or cause of noise. A more realistic nonlinear models, all input to and output from our better behaved forcing function is which we have every reason to ex- otherwise closed system. solar energy. We have been ham- pect will be required to describe On many semi-arid rangelands pered a great deal in the past by real world events. The same basic we have reason to believe that be- the fact that climatologists prefer analytical procedure, however, can cause of low fixation and low loss to express their data in terms of approximate nonlinearities and dis- rates it may be possible to approach some sort of averages. Weather, continuities through linear seg- the study of nitrogen transfer by a however, is not average, but prob- ments (Bellman and Roth, 1966). closed system approach with only abilistically variable, i.e., stochastic, With such a model in hand, vari- minor errors. We know, however, and in a study of the effect of forc- ous forms of sensitivity analyses can that carbon cycling and energy ing functions on the operation of be made. One can investigate stage transfers must be considered an the ecosystem we need to describe by stage the effect of modifying the open sys tern. A knowledge of climate by the parameters which system; i.e., one can change a co- the carbon dioxide fixation rate point out these probabilistic prop- efficient of the model to determine through studies then erties. There are various ways to the overall effect on the compart- becomes an important part of a represent climate by the character- ments many stages later. total systems study. In addition, istics which determine its variabil- losses of carbon and energy from the ity so that it can be used in com- Spatial Relationships require studies of plant puter simulation (e.g., Pattison, The matrix presented in Fig. 1 and animal metabolism, and losses 1965), but we will not go into these methods here. represents changes in time. In of soil moisture require studies of trophic - dynamic ecology, point evapotranspiration to elucidate In the past few paragraphs I have space is usually assumed. If we ex- losses from the various compart- described an approach which repre- panded the matrix in a third di- ments to the outside atmosphere. sents mathematically the function of a range ecosystem. The core of mension representing spatial dis- this approach begins with the tributions we would then have a Forcing Functions constant-coefficient closed system representation which would cover In ecology, the text by Dauben- which is represented in the “n x n” various areas. People other than mire (1947) represents the study of matrix of constant transfers be- mathematicians ordinarily consider the effects of environmental forces tween “n” compartments. This on components of the ecosystem. In a space as being distributed; that is, basic system was first expanded to the language of systems engineering, from any point to any other point include spatial relationships, fur- such outside forces which cause it is possible to be at any intermedi- changes in the system are called ther expanded to allow inputs from ate location. The mathematics of forcing functions. The time re- outside the system primarily in the such a system, however, become quired for the system to return to form of carbon dioxide fixation, quite complex. It would be much “normal” after it has been influ- and outputs from the system pri- easier mathematically to consider enced by some outside force is called marily in the form of carbon diox- space as lumped so that pastures, transient time and the “normal” ide release and evapotranspiration. soil mapping units, etc., become situation is called the steady state. Such a system would become quite discrete units. By analyses of the output of a sys- stable were it not for such influ- 320 JAMESON ences as rainfall and solar energy, “In engineering systems models however, that not only ranchers but which shock the system out of its have been built upward from avail- city dwellers as well seem to be able steady state. able knowledge about separate to understand the basic concepts components. Designing a system of trophic-dynamic ecology much model upward from identifiable System Behavior more easily than those of succes- and observable pieces is a sound sional ecology, and it appears from How do such systems behave? procedure with a history of success. For many range ecosystems manip- In economics, models have often the public and congressional sup- ulation of grazing animals causes a been constructed working back- port of the IBP that trophic-dy- significant change in the nature of ward from observed total systems namic ecology can be a program the producer compartment of the results. Even as a theoretical goal, which is much easier to “sell” than ecosystem. This impact of grazing there is no evident reason to be- successional ecology. Nevertheless, on range plants has, of course, been lieve that the inverse process of much of our background informa- the central theme of range manage- going from total-system behavior tion is in terms of successional theo- ment. If we had a study area, how- to the characteristics of the parts ries, and to make greatest use of is possible in the kinds of compli- ever, which has reached some equi- this information we should seek in- cated, noisy systems that are en- tegration of the various schools of librium with grazing, the year to countered. . . .” year changes can be considered to thought. be random events. The annual Computer simulations of a great Several years ago a prominent values in a purely cyclic system number of biological phenomena Southwestern rancher asked if there show no change and are not par- are becoming more and more com- wasn’t some way to include new ticularly useful for systems analysis. mon, and proper use of simulation ideas, such as studies, There are, however, changes within techniques can be very effective in in range research programs. Cer- years. This points out that in the resource management planning. An tainly ranchers are extremely in- study of an ecosystem which is rela- example in range management is terested in how much energy and tively stable we can probably learn the work of Goodall ( 1969). Exam- matter flows from the producer more by a study of seasonal rather ples of several simulators in other compartments to the large herbi- than annual effects. fields are cited by Watt (1966, 1968). vore compartments, much more so The seasonal changes in any pop- Simulators and other models are that they are in the successional ulation, regardless of how complex useful in organizing and describing stage of a particular range, and we they may be, can be represented to existing knowledge about a particu- all are concerned about how our any arbitrary accuracy by a series lar system, and point out areas technological disturbances of some of sine and cosine terms. Such where new studies are needed. They compartments of the ecosystem may equations, although they can de- may include analytical techniques influence other compartments of scribe the behavior of a system, do such as described in this paper or the ecosystem in which we live. In not help show how it works. As techniques borrowed from business addition, properly formulated and we learn more about the system we and economics (e.g., Hein, 1967), operating models of trophic-dy- are able to develop more mechanis- but generally are built from namic and other systems allow us tic models; that is, we are able to many simple relationships, utilizing to explore many land management predict more and more precisely knowledge and concepts of individ- alternatives without actually apply- the response to various inputs, add uals or teams of individuals who ing treatments in the field. This terms to the equations describing are thoroughly experienced in a could be an extremely valuable tool. system behavior as a function of particular area. In short, useful At the moment we are not pre- these inputs, and delete terms show- simulators are built not so much pared to incorporate large pieces ing responses as a function of time. from complex techniques as they of trophic-dynamic ecology into are from experience and hard work. land management agencies’ policies, Models and Simulators particularly since the first attempts New Land Use Policies and We have progressed from a rather to be realistically complex in such Research Possibilities simple constant-coefficient, closed investigations are just now begin- system model to a spatially dis- In the beginning of this paper I ning. I think it is appropriate for turbed, nonlinear, open system with stated that successional ecology has, land managers, both public and random environmental effects and in the past, been so useful in range private, to encourage research in system responses which are func- management that it has, in fact, be- new aspects of ecology and to begin tions of probabilistic inputs. This come embedded in the policy to explore new ways which these build up from simple to complex of land management agencies. modern concepts can be incorpo- models has been a most useful ap- Whether or not trophic-dynamic rated into land management guide- proach in systems analysis and sim- ecology can be utilized in resource lines. ulation in many fields. For exam- management to the same degree re- As in any new field there will be ple, Forrester (1961) observed: mains to be seen. I have observed, many false starts and inefficiencies. POLICY AND ECOLOGY 321

Obviously the skills required soon new concepts of ecology will more mets [ed.] Concepts and models of exceed the abilities of any one in- likely be profitable than many biomathematics: Simulation tech- dividual, and team research is re- things which we have done in the niques and methods. Marcel Dekker, quired. An ideal institution for past in rangeland research and will Inc. such complex research would have provide a basis for rational resource HEIN, L. W. 1967. The quantitative approach to managerial decisions. flexibility and access to a wide decisions in the future. Prentice-Hall. Englewood Cliffs, N. J. variety of individual specialties, and 386 p. Literature Cited at the same time a critical mass of LINDEMAN,R. L. 1942. The trophic- interdisciplinarians with dedication BELLMAN, R., AND R. S. ROTH. 1966. dynamic aspect of ecology. Ecology to, and time for, the necessary inte- Segmental differential approxima- 23:399418. gration between the various spe- tion and biological systems: An MARGALEF, R. 1968. Perspectives in cialties. Large universities (or sev- analysis of a metabolic process. J. ecological theory. The Univ. Chi- eral nearby universities) and their Theoret. Biol. 11: 168-176. cago Press. 111 p. associated federal research organi- BERMAN, M., M. F. WEISS, AND E. MILSUM, J. H. 1966. Biological con- SHAHN. 1962a. The routine fitting zations do have a wide variety of trol systems analysis. McGraw Hill. of kinetic data to models. A mathe- N.Y. 466 p. intellectual skills, although we are matical formalism for digital com- ODUM, E. P. 1959. Fundamentals of finding that in certain specialty puters. Biophys. J. 2:275-287. ecology. 2nd Ed. W. B. Saunders areas people do not exist even in BERMAN, M., M. F. WEISS, AND E. Co. 546 p. five universities. This complex ef- SHAHN. 1962b. Some formal ap- PATTISON,A. 1965. Synthesis of hourly fort, however, requires new con- proaches to the analysis of kinetic rainfall data. Water Resources Res. cepts in integration, unity of pur- data in terms of linear compart- 1:489-498. pose, continuity of personnel, and mental systems. Biophys. J. 2:289- ROSEN, R. 1967. Optimality princi- administrative efficiency which pre- 316. ples in biology. Butterworths, Lon- viously have not been universal at- BLEDSOE, L. J., AND G. M. VAN DYNE. don. 198 p. tributes of universities. We find 1968. Evaluation of a digital com- SMITH, R. L. 1966. Ecology and field puter method for analysis of com- biology. Harper and Row. N.Y. that necessary structure and team- partmental models of ecological sys- 686 p. work can be developed once the tems. Ridge Nat. Lab. TM-2414. TANSLEY, A. G. 1935. The use and individuals concerned become con- CLEMENTS, F. E. 1916. Plant succes- abuse of vegetational concepts and vinced of the urgency of the prob- sion: an analysis of the development terms. Ecology 16:284-307. lems and the benefits of cooperative of vegetation. Carnegie Inst. Pub., WATT, K. E. F. 1966. Systems analy- research. Washington, 242: 1-512. sis in ecology. Academic Press. N.Y. The payoff from such research DAUBENMIRE,R. F. 1947. Plants and 276 p. could be great, or, like any research, environment. John Wiley and Sons, WATT, K. E. F. 1968. Ecology and Inc., New York. 424 p. resource management. McGraw-Hill. the direct payoff in terms of ap- FORRESTER, J. W. 1961. Industrial N.Y. 450 p. plied management practices could dynamics. The M.I.T. Press. 464 p. WEAVER, J. E., AND F. E. CLEMENTS. be nil. It appears very probable, GOODALL, D. W. 1969. Simulating 1938. Plant ecology. McGraw-Hill. however, that investigations into the grazing situation. In F. Hein- N.Y. 601 p.

THESIS: UNIVERSITY OF WYOMING

Preference and Utilization Trends by Cattle on Grass-Forb Vegetation in the Northern Big Horn Mountains, Wyoming, by Lynn D. Todd. M.S. Range Management, 1969.

Vegetative preference and trend of utilization shown by The major preferred forbs were Turuxucum officinule, Ago- cattle on the northern Big Horn Mountains of Wyoming seris glauca, Polygonum bistortoides, and Amica spp. There was measured during the summer of 1968. was some difference in preference shown for forbs between Two study areas were selected. The first was at an aver- the two elevational sites. age elevation of approximately 8,600 feet while the second Some degree of utilization trend was shown for most spe. was at an average elevation of 9,300 feet. The livestock preferred grasses and sedges over forbs. The ties. The most definite and most explainable trends were major preferred grasses and grasslike plants were Agropyron found to be in forbs. Utilization trend in grasses and sedges spp., Koeleria cristata, Pea spp., Stipu spp., and Curex spp. were not as explicit.