BioScience July/August 1990 American In.stitate of Biological Sciences Vol. 40No. 7 Long-Term Ecological Research and the Invisible Present Uncovering the processes hidden because they occur slowly or because effects lag years behind causes
John J. Magnuson
ll of us cap. sense change-the when a time ·series of annual values is reddening sky with dawn's In the absence of long opened to 10 years, to 50 years, or to A. new light, the rising strength the length of the record-132 years of lake waves during a thunderstorm, term research, serious the invisible present is put into con and the changing seasons of plant text and can be better understood. flowering as temperature and rain af misjudgments can With ten years of record, it is ap fect our lands~apes. Some of us see occur in attempts parent that the duration of ice cover longer-term, events and remember in 1983 was 40 days or so shorter that there was less snow last winter or to manage than <;1ny of the other nine years and that fishing was better a couple of far exceeded the typical range of vari yea.rs ago. But it is the unusual person the environment ation. Also, we see that the duration who senses with any precision of ice cover varies considerably from changes occurring over decades. At year to year. With 50 years of record, this time scale, we are inclined to deforestation. In the absence of the it becomes apparent that 1983 and think of the world as static, and we temporal context provided by long other El Nino years tended to have typically underestimate the degree of term research, serious misjudgments shorter durations of ice cover (Rob change that does occur. Because we can occur not only in our attempts to ertson 1989). Now the phenology of are unable directly to sense slow understand and predict change in the ice cover is linked to a major feature changes and because we are even world around u,s, but also in our of global climate, the southern ocean more limited in our abilities to inter attempts to manage our environment. oscillation index (Mysak 1986, pret their cause-and-effect relations, Although serious accidents in an in Quinn et al. 1978). With 132 years of processes acting over decades are hid stant of human misjudgment can be record (Robertson 1989), a general den and reside in what I call "the envisioned that might cause the end warming trend becomes visible that invisible present" (Magnuson et al. of Spaceship Earth (sensu Fuller was invisible with the 10- and 50-year 1983). 1970), destruction is even more likely records. The invisible present is the time to occur at a ponderous pace in the A little ice-age ended in approxi scale within which our responsibili secrecy of the invisible present. mately 1890 (Lamb 1977, Wahl and ties for planet earth are most evident. Lawson 1970), as reflected by the Within this time scale, ecosystems Revealing the invisible present decrease in the duration of ice cover. change during our lifetimes and the In the most recent years, there is a lifetimes of our children and our Long-term or sustained research can hint that another warming has begun, grandchildren. This is the time scale open for view the events of the invis perhaps signaling C02 -induced of acid deposition, the invasion of ible present, much like timeclapse global climate warming (Liss and non-native plants and animals, the photography reveals the bloomtng of Crane 1983). The entire time series introduction of synthetic chemicals, a flower or the movement of a snail. A shows that the 1983 ice cover was the C02-induced climate warming, and single year's observation of any struc shortest observed in the entire 132 ture or event, such as the duration of years. Thus each increase in the pe ice cover on Lake Mendota in the riod of record revealed John J. Magnu~on, a fisheries ecologist, is new insights a professor of zoology and is the director winter of 1982-1983 (Figure 1, top), about the invisible present and made of the Center for Limnology at the Uni from a long-term perspective is rela the condition in 1983 more under versity of Wisconsin, Madison, WI tively uninteresting in that it provides, standable and more interesting. 53706. © 1990 American Institute of in itself, no insight into the long-term As with observational studies, field Biological Sciences. behavior of a natural system. Yet experiments also can be susceptible to july/August 1990 495 serious misinterpretation if they are not trogen addition to plots in an old-field Funded by the National Science conducted in the context of long-term environment at the Cedar Creek Nat Foundation's Division of Biotic Sys ecological research (Tilman 1989). Ni- ural History Area site in Minnesota tems and Resources, the LTER sites illustrates this point (Figure 2). include temperate and tropical for If the influence of nitrogen was ests, prairie, desert, alpine and arctic judged in the first year after fertiliza tundra, agricultural fields, lakes, riv tion, ecologists might have concluded ers, coastal wetlands, and an estuary. that fertilization increased perennial At each site, major questions are ad ragweed (Ambrosia coronopifolia) dressed related to patterns and con and bluegrass (Poa pratensis) and had trols of primary production, food no influence on blackberry (Rubis webs, population abundance and dis sp.). The five-year time series is more tribution, organic matter accumula revealing; perennial ragweed re tion, and biogeochemical cycling, as sponded immediately and then dra YEAR matically declined to control levels, 240r------~ PERENNIAL bluegrass responded more positively RAGWEED in the second year and by the fifth 180 year was significantly less abundant than in control plots, and blackberry • High Nitrogen showed no change in the first year but 120 had a highly significant increase in o Control abundance by the fifth year (Tilman 60 1988). Therefore, response to nitro
gen fertilization is time dependent. (\j The responses after one, three, or five E 0 years are each statistically significant 'Cl and repeatable, but each differs signif Q) 80 G•EL NINO EVENTS icantly from the other years. This 0 150 c SO,YIEAfllll time series displays featUres invisible c 60 '0 130 from one- or two-year experiments. c :::J .,.. Clearly, a one-year experiment, even .c 0 110 40 '0 though its results would be repeatable
496 BioScience Vol. 40 No. 7 well as questions related to distur TIME SCALES bance frequency and effect. A base of PHYSICAL common measurements and ques RESEARCH RESET BIOLOGICAL tions also lays the groundwork for YEARS SCALES EVENTS PHENOMENA new analyses and generalizations • Evolution of across different ecosystems relatively 10 5 100 MILLENN lA Species unencumbered by the unique charac PALEO e Continental 10 4 10 MILLENNIA ECOLOGY 8 Glaciation • Bog Succession ter of each ecosystem. In addition, the LIMNOLOGY • Forest Community Migration accumulating record and experience 103 MILLENNIUM • Species Invasion • Climate Change provide a temporal and spatial con • Forest Succession '10 2 CENTURY . • forest -Fires text for individual researchers need i • COa clltnat, • ·culturol ing such a base for their experiments. Warming Eulrophlcation lto' DECADE e Sun Spot cycle • Hare Population ; LTER sites are regional and na : ILTER • et Ntno • Proirle.Succ.ession' tional research facilities for long-term !too YEAR •.Prairie .f'ir.es • Annual Plants or sustained ecological research. Insti : It Lake Turnover • Plankton : . Succession tutions operating LTER sites encour ito-t "MONTH" : • ocean Upwelling • Storms • A I go I Bloom age collaborative research by scien 2 10- "DAY" MOST • Die I Lighl Cycle • Die! Migration tists at other institutions and the use ECOLOGY • Tides of the sites by visiting investigators. to- 3 "HOUR" Paleoecology and paleolimnology complement long-term observational Figure 3. The Long-Term Ecological Research program supported by the National study because they provide an even Science Foundation focuses on time scales of years to decades to a century in a major longer term context for interpreting effort to understand ecological structure and function hidden in the invisible present. the present. Because such studies have Time scales relevant to various physical events and biological phenomena are taken from lower temporal, spatial, and biotic sources including Delcourt et al. (1983), Haury et al. (1978), and Stommel (1963, 1965). resolution than is possible with bio logical observations and experiments, they in turn are complemented by does not die back each year. After fish 4000 years ago (Ives 1978, Ives and long-term research. Many important hatch or trees germinate, annual mor Hansen-Bristow 1983, Nichols ecological changes and processes are talities reduce the total number left in 1982). Some evidence for this hypoth played out over a long time scale, and the cohort, but individuals grow esis is provided by a 1905 burn at the they are often the ones with human larger. The accumulated biomass of Niwot treeline, where more than 80 relevance (Likens 1983, 1989). the cohort reaches a maximum in the years later, the forest shows few signs year when the product of the number of recovery. This interpretation is Long-term lags between cause of organisms still living and their controversial, and Shankman (1984) and effect mean body mass is greatest (Beverton has projected from seedling and sap and Holt 1957, Pitcher and Hart ling establishment that recovery will Time lags of longer than a year can 1982 for fish). Before the maximum, yet occur given sufficient time in the exist between cause and effect or until there are many trees but they are absence of disturbance. ecological responses to a disturbance small; after the maximum, the trees Relict biota also persist into the permeate natural systems. These time are large but are few in number. The future after conditions have changed lags occur for many reasons: certain time lag between the year when a over time scales of only a few years. biological and physical processes sim cohort is formed and when it reaches The extensive meadows dominated ply take time, biological relicts persist maximum biomass depends on the by the sedge Kobresia on the Niwot even after conditions change, move mortality and the growth rates of Ridge are thought, on the basis of ments across the landscape take time, organisms in that particular popula their soil characteristics, to have been the simultaneous occurrence of two tion; for many fish in freshwater in place for centuries. Kobresia pre or more necessary conditions for an lakes, the time lag is two to four fers sites free of snow in winter; it event or process to occur can be rare, years, but for long-lived trees it may rarely reproduces sexually on Niwot and a chain of events accumulates the be 200 years or longer. · Ridge but instead maintains itself lags between cause-and-effect events. through vegetative tillering. Pat Web Each of these reasons for time lags Biological relicts. A period of success ber and his students (Emerick 1976, will be illustrated with examples from ful tree reproduction can produce a Keigley 1987, Webber et al. 1976) LTER sites. forest that may persist into a future assessed the resistance of the Kobresia that changing conditions have made community to environmental change Processes taking time. The accumula unsuitable for reproduction. The tree by increasing snowpack with snow tion of biomass is a good example of line at the Niwot Ridge/Green Valley fences. In the first two years after a process that simply takes time. The Lakes LTER Site in the Rocky Moun greater snowpack, the plant produced example for a cohort of trees is the tains of Colorado has been consid more leaves and appeared to be vig same as for a year-class of fish or for ered to be a relict treeline, established orous. The plant apparently reallo any population of organisms that live in the more favorable climate of the cated its resources to stature rather a number of years and whose biomass altithermal period approximately than to vegetative reproduction when july/August 1990 497 But the BIG the snowpack was present. MUSKELLUNGE snowpack prevented the generation LAKE of new shoots, and within five years 350 Kobresia was sparse and by ten years had completely disappeared. A time lag, linked causally to the biology of this particular species, is evident in the disappearance of Kobresia; again, as with Tilman's fertilization experi ments, a conclusion made in the first two years after the manipulation would have been misleading. ALKALINITY PROFILE (microequivalents per liter) Movement across landscapes. Land scapes in which ecosystems occur Figure 4. The slow movement of groundwater across the landscape allows time for have spatial dimensions that influence chemical reactions to increase the alkalinity of the water entering the lower lake at the the temporal ones. Movement of wa North Temperate Lake LTER Site in Wisconsin (adapted from Kenoyer 1986). Far than ter, materials, and organisms takes more acid buffering capacity is acquired from the till, which is low in carbonates, time and introduces lags into ecosys would have been expected if flows were faster. tem changes. Classic examples are the time for dispersal of exotic plants and a product of conditions animals across the landscape. The Eu the alkalinity of the water increases be, in part, the region was logged ropean starling (Sturnus vulgaris) dis dramatically before entering the present before near the turn of the cen persed from the New York City area lower lake (Kenoyer 1986; Figure 4). and burned in 1896 to western New Jersey by Owing to this slow movement of tury. 1908 and to western Ohio by 1926 groundwater down the landscape Time lags can oc (Elton 1958). The sea lamprey (Petro from lake to lake, each lake succes Rare coincidence. requires the myzon marinus) spread from Lake sively lower in the flow system has a cur because a process of two or more low Ontario after the Welland Canal was higher alkalinity and concentration of coincidence events; in some cases, built in 1829 into Lake Erie by 1932 solutes. Some of the groundwater probability may pass before the (Pearce et al. 1980) and into Lakes now entering the lakes low in the many years together. In the short Huron, Michigan, and Superior by landscape may have been in the flow events occur at the Central Plains the late 1930s (Smith and Tibbles system 100 years or more and could grass steppe 1980). The Asiatic clam (Corbicula fluminea Philippi) was first observed in the Columbia River in 1938; by 1960 it had reached southern Illinois and, by 1975, southern Wisconsin via dispersal up the Mississippi River (Thompson and Sparks 1977). The Asiatic clam is thought to be inducing ecological changes in the rivers of time lag of 50 North America after a (J) years.l (J) Groundwater movement is slow at BioScience Vol. 40 No. 7 498 Experimental Range LTER Site in and three years before the lowest wa greatest grazing pressure on their Colorado, plant communities are ter clarity was observed. When the prey. These changes were not unex dominated by a perennial grass, blue perch reached maximal biomass and pected (Brooks and Dodson 1965, grama (Bouteloua gracilis). Distur moved into the open water, they Carpenter 1988, Carpenter et al. bances in the shortgrass steppe occur preyed on and reduced the abundance 1985, Henrikson et al. 1980, Hr over many spatial and temporal of the microscopic herbivores that eat bacek 1958, Hrbacek et al. 1961, scales, but a particular pair of condi the planktonic algae. The perch Northcote 1988), but we were sur tions must occur before blue grama induced reduction in herbivores less prised by their magnitude. can recover. ened grazing pressure on the midwa Earlier, Joan Baker and I (Baker Establishment of seedlings requires ter algae, and these algae increased in and Magnuson 1976) had observed a that viable seeds and adequate soil abundance. With more algae in the decrease in water clarity of Crystal moisture be present. Both conditions water column, light penetration was Lake from the early measurements by are rare in these semiarid grasslands; reduced and water clarity declined E. A. Birge and C. Juday in the 1930's viable seeds are produced approxi dramatically. As the perch year-classes and by Baker in 1973. We had con mately every seven years and appro aged, their biomass and numbers de cluded that a gradual change over 40 priate soil moisture approximately clined and the changes rever~ed. years had occurred owing to changes every eight years. The two conditions Most of this two- to three-year lag in human use. It now appears that a are independent. Debra P. Coffin and resulted from the time it takes for a much more rapid oscillation in water William K. Lauenroth of Colorado year-class of fish to obtain maximal clarity occurs due to the formation of State University devised a model to biomass. It is at the age of maximal strong year-classes of perch every few simulate the long-term changes of biomass that the perch exerted the years. Again Baker's short-term re- blue grama on small patches over 500 years (Coffin and Lauenroth 1990; YEAR Figure 5). 1981 1982 1983 1984 1985 1986 I I During the 500-year simulation, the plot was disturbed four times by cattle fecal 50 pats that killed all the blue Perch grama. Fecal pats are the most fre quent small-scale disturbance in Year Class shortgrass plant communities grazed Strength ...... by domestic cattle and serve as a 0 I I model of larger scale disturbances such as plowing. The time lags that - resulted were, in sequence, approxi Perch mately 10, 20, 80, and, at the end of Pelagic t the record, at least 35 years. This 10000 model provides some insight as to Adult ~ why larger sections of the shortgrass Abundance t=~·~====~c_------~------=~~ steppe that were disturbed by plow ing 50 to 100 years ago have not yet recovered. Dominant Chains of events. Time lags also are Herbivore generated because a cause-and-effect chain of events accumulates the lags Abundance from each link in the chain. Changes (#/liter) in water clarity provide a good exam ple (Figure 6). In Crystal Lake, at the North Temperate Lake LTER Site op Water erated by the University of Wiscon sin-Madison, we observed a decrease Clarity in water clarity over a three-year pe ( m) riod from approximately 11 m to 6 m in 1984.2 This change was initiated by the formation of strong year-classes of 2-3 years yellow perch (Perea flavescens), two TIME LAG 2 ]. ]. Magnuson, M.P. Anderson, D. E. Arm Figure 6. Time lags from a chain reaction in a food web occur because a fish year-class strong, C.]. Bowser, T. M. Frost, and T. K. takes several years to reach maximum biomass and thus exert maximal influence on its Kratz, 1990, abstract submitted for INTECOL prey populations. Abundant perch reduce the abundance of herbivorous zooplankton, meeting, Yokohama, Japan. causing the algae to thrive, in turn decreasing water clarity. · July/ August 1990 499 search, with only one recent year for Wisconsin) to intensive recreational use, Ives, ]. D. 1978. Remarks on the stability of comparison, did not penetrate the 1924-1973. Trans. Wis. Acad. Sci. Arts Lett. timberline. Pages 313-317 in C. Troll and realm of the invisible present. 64: 47-61. W. Lauer, eds. Geoecological Relations be Beverton, R. H.]., and S.]. Holt. 1957. On the tween the Southern Temperate Zone and the Dynamics of Exploited Fish Populations. Tropical High Mountains. Erdwissenschaft Conclusions Fishery Investigations. Series II, vol. XIX. liche Forschung. Franz Steiner, Wiesbaaden, Ministry of Agriculture, Fisheries and Food, FRG. The natural world is dynamic, not Her Majesty's Stationery Office, London. Ives, J.D., and K. ]. Hansen-Bristow. 1983. Brenneman,]., ed. 1989. Long Term Ecologi Stability and instability of natural and mod static, and the older each of us gets, cal Research in the United States: A Network ified upper timberline landscapes in the Col the more apparent is this truth. Time of Sites 1989. 5th ed. Long-Term Ecological orado Rocky Mountains, U.S.A. Mountain lags in ecological systems are the rule; Research Network, Forest Science Depart Research and Development 3: 149-155. they separate cause and effect to con ment, Oregon State University, Corvallis, Keigley, R. B. 1987. Effect of experimental fuse our interpretation of the natural OR. treatments on Kobresia myosuroides with Brooks, J. L., and S. I. Dodson. 1965. Preda implications for the potential effect of acid world, which can appear fickle and tion, body size, and composition of plank deposition. Ph.D. dissertation, University of unsettled. Increasingly long records of ton. Science 150: 28-35. Colorado, Boulder. ecosystem structure and process and Callahan, J. T. 1984. Long-term ecological re Kenoyer, G.]. 1986. Evolution of groundwater long-term experiments expose new search. BioScience 34: 363-367. chemistry and flow in a sandy aquifer in Carpenter, S. R. 1988. Transmission of vari northern Wisconsin. Ph.D. dissertation, Uni phenomena and allow greater under ance through lake food webs. Pages 119-135 versity of Wisconsin-Madison. standing. The Long-Term Ecological inS. R. Carpenter, ed. Complex Interactions Lamb, H. H. 1977. Climate: Present, Past, and Research Program formalizes this hu in Lake Communities. Springer-Verlag, New Future. val. II. Climatic History and the man experience. Such knowledge is York. Future. Methuen and Co., New York. sure to help us in facing the problems Carpenter, S. R., J. F. Kitchell, and J. R. Hodg Likens, G. E. 1983. A priority for ecologists. son. 1985. Cascading trophic interactions Bulletin of the Ecological Society of America ahead. Our lack of understanding of and lake productivity. BioScience 35: 634- 64: 234-243. events and processes in the time scale 639. __ . 1989. Long-Term Studies in Ecology: of decades has been and will in the Coffin, D.P., and W. K. Lauenroth. 1990. A Approaches and Alternatives. Springer future be costly to human society. gap dynamics simulation model of succes Verlag, New York. Operating Space Ship Earth blind to sion in a semiarid grassland. Ecol. Model. Liss, P. S., and A.]. Crane. 1983. Man-Made 49: 229-266. Carbon Dioxide and Climatic Change-A the invisible present is unacceptable. Delcourt, H. R., P. A. Delcourt, and T. Webb Review of Scientific Problems. Geo Books, The invisible present is beginning III. 1983. Dynamic plant ecology: the spec Norwich, England. to be penetrated by researchers and trum of vegetational change in space and Magnuson, J. J ., and C.]. Bowser. 1990. A agencies with an increasing awareness time. Quaternary Science Reviews 1: 153- network for long-term ecological research in of the importance of serious and co 175. the United States. Freshwater Bioi. 23: 137- Elton, C. S. 1958. The Ecology of jnvasions by 143. ordinated research at the time scales Animals and Plants. Methuen and Co., Lon Magnuson, J. ]., C.]. Bowser, and A. L. of years to decades. LTER is the most don. Beckel. 1983. The invisible present: long extensive. Emerick, ]. C. 1976. Effects of artificially in term ecological research on lakes. L & S creased winter snow cover on plant canopy Magazine, University of Wisconsin, Madison architecture and primary production in se Fall 1983: 3-6. Acknowledgments lected areas of the Colorado alpine tundra. Mysak, L. A. 1986. El Niiio, interannual vari Ph.D. dissertation, University of Colorado, ability and fisheries in the northeast Pacific I thank the National Science Founda Boulder. Ocean. Can. f. Fish. Aquat. Sci. 43: 464- tion for having the leadership and the Franklin, ]. F., C. S. Bledsoe, and J. T. Calla 497. insight to establish a program for a han. 1990. Contributions of the Long-Term Nichols, H. 1982. Review of the late Quater Ecological Research Program. BioScience nary history of vegetation and climate in the network of Long-Term Ecological 40: 509-523. mountains of Colorado. Pages 27-33 in]. C. Research Sites. I thank Patrick J. Fuller, R. B. 1970. Operating Manual for Halfpenny, ed. Ecological Studies in the Col Webber (Niwot Ridge/Green Valley Spaceship Earth. Touchstone, New York. orado Alpine: A Festschrift for John W. Lakes LTER Site), who made unpub Haury, L. R., J. A. McGowan, and P. H. Marr. Occasional Paper 37, Institute of Arc lished materials available for this pa Weibe. 1978. Patterns and processes in the tic and Alpine Research, University of Colo time-space scales of plankton distributions. rado, Boulder. per. I thank Donald E. Chandler, Pages 277-328 in J. H. Steele, ed. Spatial Northcote, T. G. 1988. Fish in the structure Cheryl M. Hughes, and Mary L. Pattern in Plankton Communities. NATO and function of freshwater ecosystems: a Smith of the University of Wisconsin Conference Series IV: Marine Sciences 3. "top-down" view. Can. f. Fish. Aquat. Sci. in Madison for preparation of the Plenum, New York. 45: 361-379. figures and text. This article was Henrikson, L. H., G. Nyman, H. G. Oscarson, Pearce, W. A., R. A. Braem, S. M. Dustin, and and J. E. Stenson. 1980. Trophic changes ]. ]. Tibbles. 1980. Sea lamprey (Petromyzon based on a talk presented at a 6 without changes in external nutrient loading. marinus) in the lower Great Lakes. Can. f. November 1987 briefing at the Na Hydrobiologia 68: 257-263. Fish. Aquat. Sci. 37: 1802-1810. tional Science Foundation in Wash Hrbacek, J. 1958. Density of the fish popula Pitcher, T. ]., and P. B. Hart. 1982. Fisheries ington, DC, and in the LTER Sympo tion as a factor influencing the distribution Ecology. AVI Pub!., Westport, CT. sium at the Ecological Society of and speciation of the species in the genus Quinn, W. H., D. 0. Zopf, K. S. Short, and Daphnia. Pages 794-795 in Proceedings of R. T. W. Kuo Yang. 1978. Historical trends America meeting in August 1988 in the XVth International Congress of Zool and the statistics of the southern oscillation, Davis, CA. ogy. Section X, Paper 27. El Niiio, and Indonesian droughts. Fish. Hrbacek, J., M. Dvorakova, V. Korinek, and L. Bull. 76: 663-677. Prochazkova. 1961. Demonstration of the Robertson, D. M. 1989. The use of lake water References cited effect of the fish stock on the species compo temperature and ice cover as climatic indica sition of zooplankton and the intensity of tors. Ph.D. dissertation, University of Wis Baker, J., and J.]. Magnuson. 1976. Limnolog metabolism of the whole plankton associa consin, Madison. ical responses of Crystal Lake (Vilas County, tion. Verh. Int. Ver. Limnol. 14: 192-195. Shankman, D. 1984. Tree generation following 500 BioScience Vol. 40 No. 7 fire as evidence of timberline stability in the Call for Nominees Colorado Front Range, U.S.A. Arct. Alp. Res. 16: 413-417. for the 1991 Smith, B. R., and J. J. Tibbles. 1980. Sea lam prey (Petromyzon marinus) in Lakes Huron, AIBS Distinguished Service A ward Michigan and Superior: history of invasion and control, 1936-78. Can. f. Fish. Aquat. Sci. 37: 1780-1801. Since 1972 the AIBS Distinguished Service Award has been presented to Stommel, H. 1963. Varieties of oceanographic individuals who have contributed significantly in the service of biology. The experience. Science 139: 572-576. principal criteria for this award are that the recipients shall have made ah __ . 1965. Some thoughts about planning outstanding contribution toward: the Kuroshio survey. In Proceedings of a Symposium on the Kuroshio. Tokyo, Japan. 29 October 1963. Oceanographic Society of • advancing and integrating the biological disciplines, Japan and UNESCO. e applying biological knowledge to the solution of world problems, artd Swanson, F. J., and J. F. Franklin. 1988. The Long-Term Ecological Research Program. o introducing pertinent biological considerations that improve public policy EOS: Transactions of the American Geo and planning. physical Union 69(3): 34, 36, 46. Swanson, F. J., and R. E. Sparks. 1990. Long Emphasis is placed on distinguished service. Scientific discovery per se is not term ecological research and the invisible place. BioScience 40: 502-508. included as a criterion for this award, although some nominees will carry this Thompson, C. M., and R. E. Sparks. 1977. The distinction as well. Asiatic clam, Corbicula manilensis in the Illinois River. Nautilus 91: 34-36. Previous recipients of the award have been: Tilman, D. 1987. Secondary succession and the pattern of plant dominance along experi mental nitrogen gradients. Ecol. Monogr. • 1972-Harve Carlson, George Miller, Detlev Bronk 57: 189-214. e 1973-Theodore Dobzhansky, Rene Dubos __ . 1988. Plam Strategies and the Dy namics and Structure of Plant Communities. o 1974-James G. Horsfall Princeton University Press, Princeton, New Jersey. • 1975-W. Frank Blair, Theodore Cooper __ . 1989. Ecological experimentation: o 1976-Paul B. Sears, Edward 0. Wilson strengths and perceptual problems. Pages 136-157 in G. Likens, ed. Long-Term Stud e 1977-Paul J. Kramer, Elvin C. Stakman, William C. Steere ies in Ecology. Springer-Verlag, New York. e 1978-Eugene P. Odum, Howard T. Odum, George Gaylord Simpson Wahl, E. W., and T. L. Lawson. 1970. The climate of the midnineteenth century United e 1979-Theodore C. Byerly, H. C. Chiang, Lee M. Talbot States compared to the current normals. • 1980-Arthur D. Hasler, A. Starker Leopold, Ruth Patrick Monthly Weather Review 98: 259-265. Webber, P. J.,]. C. Emerick, D. C. Ebert May, o 1981-Peter H. Raven and V. Komarkova. 1976. The impact of • 1982-George M. Woodwell increased snowfall on alpirte vegetation. Pages 201-264 in H. W. Steinhoff and J.D. e 1983-Karl Maramorosch lves, eds. Ecological Impacts of Snowpack Augmentation in the San Juan Mountains, • 1984-Arnold B. Grobman Colorado. Final Report, San Juan Ecology • 1985-Sayed Z. El-Sayed Project, Colorado State University Pub!., Fort Collins. e 1986-Garrett Hardin • 1987-Perry L. Adkisson e 1988-Donald E. Stone • 1989-Alfred E. Harper • 1990-Gene E. Likens AIBS members are invited to submit nominations for this award, which will be presented at the 1991 Annual AIBS Meeting, San Antonio Convention Center, San Antonio, Texas. Each nomination must be accompanied by a complete curriculum vitae and a statement of the individual's service to the biology profession. ln particular, the supporting statement should highlight the nomi nee's accomplishments in each of the three award criteria given above. Nominators should note that traditional academic vitae often omit contribu tions to public affairs. As this area is considered equally important in the overall consideration, care should be taken to bring out the nominee's relevant accomplishments. Since 1981, recipients have been limited to single individ uals, but nominations will remain active for three consecutive years, e.g., for the 1991, 1992 and 1993 awards. Send nominations (with biographies) to the AIBS Executive Director, 730 II th Street, NW,"Washington, DC 20001-4521, by 1 October 1990. july/August 1990 501 Long-Term Ecological Research and the Invisible Place The local to global spatial scales of the Long-Term Ecological Research Program Frederick J. Swanson and Richard E. Sparks he distinctive feature of the of resolution to provide context for National Science Founda Significance of research interpretation of fine-scale system be T tion's Long-Term Ecological havior and to use knowledge of finer Research (L TER) Program has been results is difficult to scale processes to explain mechanisti the opportunity to examine ecosys cally the patterns observed at coarser tem behavior on longer time scales interpret if a site's scales (O'Neill et al. 1986). than traditionally emphasized in eco context in space is In this article, we describe exam logical research (Callahan 1984, ples of LTER research activities at a Franklin et al. page 509 this issue, not understood series of spatial scales; present an Magnuson page 495 this issue, Mag example of multiscale, intersite com nuson et. al. in press, Swanson and parison of ecosystem behavior; and Franklin 1988). As Magnuson has describe multiscale research at one argued, lack of historical perspective "invisible place" where the signifi LTER site. The LTER program has can place short-term studies in the cance of results is unclear. substantially encouraged comparative "invisible present," where a lack of As LTER research addresses longer analysis across diverse ecosystems. temporal perspective can produce time scales, it has been natural to also Such intersite rese;uch is facilitated misleading conch.1sions. Similarly, the confront greater spatial scales (Del through mechanisms such as work broad significance of research results court et al. 1983). For example, veg shops, scientist exchanges during sab from a particular site is difficult to etation change at a site over a few baticals, and L TER funds used for interpret if the site's context in space years involves processes such as com pilot projects leading to larger inter (e.g., location within region-scale petition among neighboring individ site studies with separate funding. variation in disturbance regime and ual plants. Vegetation change at the However, we emphasize that LTER temperature-moisture conditions) is same site, but on time scales of cen sites were not selected and LTER sci not understood. In this sense, an iso turies and mil}ennia, also involves ence was not designed around testing lated research site may reside in an species migr:;1tion on broader spatial major hypotheses at the intersite scales. level. Further, many of the studies Consideration of broader spatial described here are not unique to Frederick J. Swanson is a principal inves scales in LTER research is fostered LTER. tigator in the Andrews LTER program, a research geologist and project leader with by: emergence of critical, large-scale the USDA Forest Service, Pacific North questions concerning ecological ef Scales of LTER Research west Research Station, and a professor in fects of global climate change ancl the Departments of Forest Science and land use at landscape and regional Research in the LTER Program oc Geosciences, Oregon State University, scales; opportunity to compare eco curs at a series of spatial scales: plot/ Corvallis, OR 97331. His primary re system properties across· the conti patch, landscape, region, continent, search interests concern the roles of land nent-spanning LTER system of sites; and globe, but the research focuses forms and geological processes in ecosys and development of regional-scale da primarily on the plot/patch and land tems. Richard E. Sparks was a principal tabases and modeling efforts using scape scales (Figure 1). Past ecological investigator in the Illinois-Mississippi LTER sites as focal points (Gosz and research has tended to focus on the River LTER program (1982-1989) and is of the an aquatic ecologist with the Illinois Nat Sharpe 1989). These factors have re spatial scales at the finer end ural History Survey's River Research Lab sulted in studies within the LTER spectrum, whereas global-change oratory. His primary research interests network at a series of spatial scales. programs emphasize very-large-scale concern the factors controlling productiv The intent of such multiscale research phenomena. L TER can help bridge ity in large, floodplain rivers. is to use knowledge of coarser scales this disparity of scales of study. 502 BioScience Vol. 40 No. 7 Plot/patch scale. Distinctions among plots, patches, and landscapes as SPACE SCALES identified here are not necessarily based on absolute size, but, instead, represent the degree of contrast and AREA (m2) RESEARCH PROGRAMS extent of interaction with neighbor ing areas. A plot or patch is an eco 1014 GLOBAL GLOBAL logical or geomorphic unit that can be SCIENCES ILTER treated as homogeneous for a partic 1012 (IGBP) ular purpose. Plots generally reside CONTINENT I within larger areas of similar make I up-a patch. Patches have edges that 1010 REGION I border adjacent areas with differing system properties, and patches can be defined within or between systems as diverse as forests, streams, and lakes. Questions concerning edge effects may be included in the study of patches, but plots are usually de signed to avoid edge effects. Much LTER research is designed and implemented at the plot scale, SAMPLE POINTS employing experimental manipula 1 oO tions and long-term observations of change in natural systems. The size of Figure 1. Spatial scales of ecology research. Shading shows scales of LTER these plots ranges from less than one concentration. square meter to experimental water sheds of more than 100 ha. Manipu lations of plots and patches have tar paths crossing landscapes. At the marsh, estuary, and eventually to the geted nutrient and water availability North Temperate Lakes and Niwot ocean. A landscape perspective is also (e.g., at the Cedar Creek [Minnesota] (Colorado) sites, the hydrological flow applied in analysis of flows of sedi site) and disturbance, including fire paths of interest pass through chains ment through experimental drainage (Konza [Kansas] and Cedar Creek of lakes and interspersed areas of sub basins at the Niwot and Andrews sites sites), erosion/deposition (Andrews surface flow (Swanson et al. 1988). (Caine and Swanson 1989). [Oregon] site), clearcut logging (Hub The flow paths of materials considered A common approach to analysis of bard Brook [New Hampshire], in landscape research at North Inlet landscapes is to scale up to landscapes Coweeta [North Carolina], and An (South Carolina) pass from forest from plot-level observations sampled drews sites), grazing by large mam through freshwater stream to salt along gravitationally determined flow mals (Konza site), cattle fecal pats (Central Plains Experimental Range ARCTIC [Colorado] site), and invasion by ex JORNADA TUNDRA otic organisms (North Temperate Lakes [Wisconsin] and Central Plains Experimental Range sites) (Franklin et al. page 509 this issue). 130m------301Lh_ Landscape scale. Landscapes contain 350m multiple patches, and landscape re 107m search concerns interactions among patches (Forman and Godron 1986, Turner 1989, Urban et al. 1987). A small watershed may be treated as a plot in terms of overall water and nutrient balances, but it is a landscape in terms of movement of materials among areas within it. Many aspects of the landscape scale of LTER work focus on flows of 2700 m materials (water, nutrients, soil, and Figure 2. Hillslope cross sections showing topographic profile of sites of soil catena/ sediment organisms) and distribu connected ecosystem studies at three LTER sites. The length of 1 m on the vertical axis tions of plants, animals, soil types, is 15 times that on the corresponding horizontal axes. CPER: Central Plains Experi and hydrologic conditions along flow mental Range. July/August 1990 503 paths passing downslope from ridge (Andrews site), and river channel ral scales, for example, El Nino and top to valley floor through a sequence change (Andrews and Bonanza Creek potential climate change during the of soil and vegetation patches. This [Alaska] sites). A common theme in next century (Gosz and Sharpe 1989). approach is employed in nutrient cy many of these studies is that spatial Scientists at other sites are studying cling, vegetation, and soil catena patterns of disturbances are strongly the dynamics of snow-tundra (Arctic studies, for example, at Central Plains controlled by landforms; for exam Tundra and Niwot sites), forest Experimental Range, Jornada (New ple, particular topographic settings tundra (Niwot site), and marine Mexico), and Arctic Tundra (Alaska) experience highest hurricane damage terrestrial (North Inlet site) interfaces. (Figure 2). The types and degrees of (Foster 1988), slopes of 32-38° steep Sampling approaches include long control of landscape position on eco ness experience greatest landslide oc term observations of the physical en system properties varies significantly currence (Guariguata 1989, Swanson vironment (e.g., seasonal snow dura among these sites. and Dyrness 1975), and areas of wide tion), soil properties, vegetation, and In the arid Jornada environment, valley floor have most extensive chan small-mammal populations along belt for example, productivity of a site is nel change. transects and series of plots crossing controlled in part by water availabil ecotones. It is hypothesized that these ity; therefore, patterns of surface wa Regional scale. LTER programs are ecotonal sites will be among the first ter runon/runoff in response to synthesizing regional data sets col to display biogeographic aspects of downslope variation in soil hydro lected by remote sensing or by field ecosystem response to climate and logic properties are critical (Whitford observation at plots. These programs land-use change. et al. 1987, Wondzell et al. 1987). are hubs of region and biome scale The brief, infrequent runoff events studies, including work on the effects Continental scale. Continent-span characteristic of the J ornada land of broad-scale disturbances, such as ning comparative research is greatly scape create patterns of net removal drought and air pollution. facilitated by the network of LTER or accumulation of organic matter The regional modeling effort of the sites extending over 11 biomes-from and nutrients along a topographic se Central Plains Experimental Range the north slope of Alaska south to quence-patterns controlled by phys LTER, for example, draws on data Puerto Rico and from Oregon east to ical processes. from more than 6000 field plots scat New England. Currently, subsets of In contrast, at the Arctic Tundra tered across the central US grasslands LTER sites are undertaking compara site, subsurface water flow in a thin from Canada to Mexico, including tive and cooperative field studies on (20-100-centimeters-thick) layer two other LTER sites (Parton et al. subjects such as effects of resource above the permafrost transports nutri 1987). In another regional study, the limitations on productivity and plant ents downslope during a three-month Andrews LTER and allied programs succession, processes and rates of thaw period each year. Because this have established a network of 0.25- wood decomposition, and invading flow is subsurface and persists through to one-hectare reference stands and species and their ecological effects. the growing season, biotic processes other permanent sample plots in the Sites for some studies, such as the for example, nutrient uptake by coniferous forests of western North resource limitations project, are se plants-control net nutrient retention America. Some plots date from as lected to represent points along a or loss in sites distributed along the early as 1915, although most began in physiognomic gradient from short slope (Shaver et al. in press). In both the 1970s. Long-term records from grass to forests. the desert and tundra examples, the these plots, which are located within The most extensive example of in interactions of topography, soil prop forests ranging from 10 to 1000 years tersite research is a 21-site (all the erties, and downslope transport proc since originating disturbance, are LTER sites plus four additional sites) esses control patterns of vegetation used in studies of forest succession study of leaf litter decomposition. and rates of biogeochemical processes, and demography and in modeling ef This study offers a first-of-its-kind although the primary controlling fac fects of land use and climate change opportunity to distinguish effects of tors differ substantially between sys on forests of the region (e.g., Franklin litter chemistry and climate on de tems. and DeBell 1988, Harmon et al. composition rates across such a broad In addition to this approach of 1990),1 range of environments. Also at the viewing landscapes as linear se Dynamics of boundaries (ecotones) continental scale, some LTER sites quences of system elements, it is im between biomes are another aspect of and research groups are contributing portant to recognize the three-dimen region-scale ecosystem research. The to research programs addressing the sional structure of landscapes. This Sevilleta (New Mexico) LTER site, effects of climate change and broad structure is conspicuous in analysis of for example, contains transitions scale air pollution on forest and fresh landform effects on disturbances. Ret among four biomes, providing an op water ecosystems of North America rospective studies of the pattern of portunity to examine the effects of (e.g., Hubbard Brook, North Tem disturbance across landscapes at climate change on the spatial distribu perate Lakes, and Harvard Forest). LTER sites and elsewhere consider tion of ecosystems at various tempo- the roles of landforms in constraining Global scale. LTER involvement in disturbance by hurricanes (Harvard global-scale issues is in its initial 1F. J. Swanson, S. Wondzell, and G. E. Grant, Forest [Massachusetts] and Luquillo 1990, manuscript submitted. stages. LTER is providing field obser [Puerto Rico] sites), landslides (Lu 2V. H. Dale and J. F. Franklin, 1990, manu vations and experimentation for veri quillo and Andrews sites), wildfire script submitted. fication of remote sensing and model- 504 BioScience Vol. 40 No. 7 ing efforts that are part of the National Science Foundation's Global Geo science Programs. To global change research programs, LTER brings ex perienced, interdisciplinary teams of ecosystem scientists, long-term data sets on environmental and biological conditions, and facilities and logisti cal support for field studies. The First ISLSCP (International Landsurface Climatology Project) Field Experi ment (FIFE) project at the Konza LTER site is a prime example of an effort to couple ground-based and re motely sensed information sampled at a series of spatial scales of resolution (see Franklin et al. 1990 for a brief description). Current interactions with scientific groups in other countries, notably in Europe, China, and South America, are an early step in expanding large scale research to an international net work of cooperating research sites and programs. This research has been facilitated in part by links among biosphere reserves in UNESCO's Man and the Biosphere Program, of which several LTER sites are a part. Intersite comparison lntersite comparisons reveal the im portance of conducting multiscale analysis of ecosystems and of distin Figure 3. Confluence of the Mississippi and Illinois Rivers 64 km upstream of St. guishing system features controlled Louis, Missouri, showing the floodplain forest, side channels, and backwaters typical of both by absolute and relative (within-site) channels. scales. The variable size and the net work structure of riverine systems provide useful examples for multi These systems have striking similari vial systems is the flood regime. scale comparison. Unfortunately, no ties in ecosystem function. In both Floods in large, temperate, lowland LTER site contains the full contin systems, streamside forests regulate rivers tend to be predictable in sea uum from small streams to large riv riverine habitat structure (downed sonality. Large drainage areas, low ers, so we cannot deal comprehen logs at any flow stage and standing gradient of the main channel, and low sively with the issue of scaling up trees during floods) and nutrient water velocity through forest vegeta through a drainage network. How availability (input of litter and nutri tion and complex channels result in ever, we can compare two study areas ents dissolved in groundwater to the slow passage of large-volume floods, in different locations within their re aquatic system; Grubaugh and An so that extensive areas of floodplain spective river networks and identify derson 1989, Sedell et al. 1989). forests may be inundated many similarities and differences in system These two systems differ greatly in months each year where landforms properties. The role of LTER within absolute scales of channel and flood permit. Consequently, many orga this analysis is to foster such· compar plain width, channel gradient, aver nisms, including fish, have adapted to isons; LTER sites were not selected age annual and peak flows, and dura using the flooded floodplain environ originally to test these ideas. tion, predictability, and areal extent ment in various life-history stages. Considering interactions of rivers of inundation of floodplain forest Overall, aquatic productivity is high and their riparian forests, we see im (Table 1). The physical differences where river systems exchange nutri portant effects of scale in comparing between sites result in substantial dif ents with highly productive terrestrial large, floodplain rivers (LTER~funded ferences in the location and timing of systems on periodically flooded flood research from 1982 to 1989 in the river-forest interactions and in the plain areas. Illinois-Mississippi Rivers [Illinois] resulting conceptual models of system In steep, mountain channels, on the site) and small, mountain streams behavior. other hand, flooding by rainfall and (Andrews site) (Figures 3 and 4). A key to contrasting these two flu- rain-on-snow events is likely to be less july/August 1990 505 these two contrasting cases. Geologic and human-constructed constraints on water flow and valley floor geo morphology cause great along-stream variation in the degree and type of river-forest interaction. We recognize this variation as we shift our view from the valley floor cross-section (plot scale) up to a scale that includes longitudinal variation in valley floor structure and its role in regulating river-forest interaction (landscape scale). In the case of the small mountain river at the Andrews site, landslides, bedrock, and alluvial fans locally constrain floodplain width and, therefore, the opportunity for river-forest interaction. Areas up stream of constrained valley-floor segments tend to have extensive river forest interaction (Figure 5). In the Illinois-Mississippi River sys tems, navigation dams and levees for Figure 4. Mountain streams in the Lookout Creek basin (Andrews [Oregon] site) with flood protection (Figure 5) are major narrow floodplain and abundant woody debris from streamside forest. constraints on valley floor processes. Areas upstream of the dams are inun dated on a continuous basis, and predictable in timing and inundates plain environment. Aquatic produc levee districts are isolated from all but much less floodplain area for shorter tivity appears to be regulated by up the major floods (occurring every 25- periods of time (Table 1). Basins with stream processes that control the 50 years), thereby eliminating the a seasonal snowmelt hydrograph, quantity and quality of nutrients and flood pulse effect (periodic inundation however, may be quite predictable in water delivered to a downstream site of floodplain areas). After many dec timing of high flows (Resh et al. and by effects of adjacent forest on ades, the impounded areas will accu 1988). The steep channels and small the channel environment (e.g., shad mulate sufficient sediment that emer drainage area facilitate rapid passage ing and input of coarse, woody de gent bars and islands form and of flood flows, which have smaller bris). become forested (Bhowmik et al. total volumes than floods produced in A major difference between the two 1986), so the flood pulse phenome much larger basins. Furthermore, in systems, therefore, is that river-forest non is reestablished. nonglaciated areas, valley floors and interactions are played out predomi A common theme at these two sites their floodplains tend to be narrow, nantly in the flooded floodplain envi is that aquatic productivity is highest because of constraints such as bed ronment of the large, lowland river where river-forest interaction is great rock outcrops and landslides from and in the channel of the steep, moun est. Aquatic productivity at a site re adjacent hillslopes. Aquatic orga tain river. Actually, both of these flects a tangled web of interactions nisms in these systems possess few, if study sites and much of the world's among physical and biological pro any, adaptations to the flooded flood- river systems contain a mixture of cesses at several absolute and relative spatial scales and at several time Table 1. Characteristics of a big, floodplain river (Illinois-Mississippi River LTER Site) and a scales. Processes related to differences small, mountain stream (Lookout Creek, Andrews [Oregon] LTER Site). in absolute spatial scales between the Mississippi two sites contribute to longer-dura Hydrologic and average River near Lookout tion flooding in the larger basin. Both characteristics Burlington, lA Creek, OR systems provide examples of land Channel width (m) 600* 10-12 form (including dams) constraints on Floodplain width (m) 3400* 6-8 the extent of river-forest interaction. Channel gradient (m/m) o.ooo7t 0.022 Important temporal dimensions of Discharge (m3/s) river-forest interactions include sea Average annual flow 1815'' 3.6 sonal patterns of hydrology and pro Peak flow 5044* 49 duction/decomposition of organic de Flood (inundation of floodplain forest) tritus and the decades-to-millennia duration (days/yr) 22 2 scale of geomorphic change. The types of contrasts represented *Grubaugh and Anderson (1988). tfremling et a!. (1989). by these mountain stream and big, *Stahl eta!. (1989) at Keokuk, IA, 1878-1988. lowland river examples have resulted 506 BioScience Vol. 40 No. 7 in a pair of theories of riverine eco systems behavior. These theories differ in the scale and processes em phasized. The flood pulse concept of river-forest interaction (Junk et al. 1989, Welcomme 1979) states that seasonal flood-flows onto floodplains strongly and positively influence the productivity of the fluvial system. This conceptual model derives from analysis of large, lowland rivers at the scale of a valley floor cross-section or individual reach of river. The river 0 0.5 1.0 continuum concept of river ecosys tems (Minshall et al. 1985, Vannote et al. 1980) emphasizes controls of upstream factors, rather than lateral floodplain systems, on properties of stream ecosystems. This concept con siders the full length of the drainage system, which typically encompasses a landscape or even an entire region. Attention to landscape and full drainage basin scales of variation in system structure and function reveals that a marriage of flood pulse and river continuum concepts is probably required to explain river-forest inter actions in most river systems (Sedell r+++l Alluvial fan Terrace et al. 1989). The flood pulse concept ~ .. accounts for lateral influences within a reach, and the river continuum con Floodplain - Channel cept offers a framework for interpre lliillilliilliJ forest /marsh backwater tation of links among successive reaches along the stream. ~ Agricultural land Multi-scale LTER studies Figure 5. Map of reaches of Lookout Creek (top) and Illinois River (bottom) valley future work floors. The Lookout Creek site shows substantial variation in the width of its valley floor as a result of geological processes operating on the valley walls. The Illinois River Research programs at several LTER site (160 km upstream of copfluence with the Mississippi River) has a more uniform sites are tackling the important, but valley floor width. Flow is from right to left. difficult, task of working across mul tiple spatial scales. The Sevilleta LTER group, for example, is using finer scales may be directed to inter • Intermediate-sized basins (200 Fourier transform infrared spectros pretation of controls on process rates, ha) that are larger than the typi copy (FTIR) to sample trace gas con whereas coarser-scale observations cal precipitation cell diameter centrations over terrestrial and aquatic can average out fine-scale variation to experience less frequent, but ecosystems at scales ranging from yield useful measures of flux between more destructive, flow events, be meters to a kilometer (Gosz et al. landscapes and the atmosphere. cause unusually large cells or 1988). This new technology is being Another multiscale project in the closely spaced cells are needed to used to measure spatial heterogeneity desert environment of Sevilleta mea produce a discharge event. of biogeochemical processes at a range sures streamflow in a nested set of 20- • Large basins exhibit spatially of scales in both homogeneous vegeta" to 350,000-hectare drainage basins to intermittent flow; some reaches tion and across ecotones. At fine sense climatic processes at a variety of have perennial flow, and others scales, the spatial patterns of bio temporal and spatial scales. Hypoth carry surface flow periodically. geochemical processes are known to eses concerning scale dependence of • Long-term gauging records on be extremely variable (Robertson et al. the streamflow regime include: the Gila (484,000-hectare basin 1988). The purpose of the multiscale area sampled) and Pecos (49,000- work with FTIR is to better character • Small basins with dimensions hectare area sampled) rivers indi ize the spatial patterns of variation so smaller than single convective cate that the magnitude of annual that future measurements can be storm cells experience several flows differs by a factor of 6.0 to scaled appropriately: observations at flow events per year. 7.4 between El Nino and La Nina july/August 1990 507 years (Molles and Dahm in Quaternary Science Reviews 1: 153-175. O'Neill, R. V., D. L. DeAngelis, J. B. Waide, press). Formann, R. T. T., and M. Godron. 1986. and T. F. H. Allen. 1986. A Hierarchial Con Landscape Ecology. John Wiley & Sons, cept of Ecosystems. Princeton University New York. Press, Princeton, NJ. As these spatial and temporal pat Foster, D. R. 1988, Species and stand response Parton, W. J., J. W. B. Stewart, and C. V. Cole. terns of streamflow become better to catastrophic wind in central New En 1987. Dynamics of C, N, P, and S in grass known, they will form an important gland, U.S.A.]. Ecol. 76: 135-151. land soils: a model. Biogeochemistry 5: 109- framework for analysis of geomor Franklin, J. F., C. S. Bledsoe, and J. T. Calla 131. han. 1990. Contributions of the Long-Term Resh, V. H., A. V. Brown, A. P. Covich, M. E. phic and ecological change of stream Ecological Research Program. BioScience Gurtz, H. W. Li, G. W. Minshall, S. R. and riparian systems of the Sevilleta. 40: 509-523. Reice, A. L. Sheldon, J. B. Wallace, and These analytical approaches are Franklin, J. F., and D. S. DeBell. 1988. Thirty R. C. Wissmar. 1988. The role of distur mainly descriptive and exploratory at six years of tree population change in an bance in stream ecology. ]. North Am. present. But they set the stage to test old-growth Pseudotsuga-Tsuga forest. Can. Benthol. Soc. 7: 433-455. ]. For. Res. 18: 633-639. Robertson, G. P., M.A. Huston, F. C. Evans, scale theory relating to ecosystem Fremling, C. R., J. L. Rasmussen, R. E. Sparks, and J. M. Tiedje. 1988. Spatial variability in processes (O'Neill et al. 1986), to S. P. Cobb, C. F. Bryan, and T. 0. Claflin. a successional plant community: patterns of detect effects of climate and other 1989. Mississippi River fisheries: a case his nitrogen availability. Ecology 69: 1517- environmental change, and to design tory. Pages 309-351 in D.P. Dodge, ed. 1524. Proceedings of the International Large River Sedell, J. R., J. E. Richey, and F. J. Swanson. better field measurement systems for Symposium (LARS). Canadian Special Pub 1989. The river continuum concept: a basis sampling at appropriate scales. lication in Fisheries and Aquatic Science 106, for the expected ecosystem behavior of very Ottawa, ON. large rivers? Pages 49-55 in D.P. Dodge, ed. Gosz, J. R., C. N. Dahm, and P. G. Risser. Proceedings of the International Large River Conclusions 1988. Long-path FTIR measurement of at Symposium (LARS). Canadian Special Pub mospheric trace gas concentrations. Ecology lication in Fisheries Aquatic Science 106. The importance of tackling ecological 69: 1326-1330. Shaver, G. R., K. J. Nadelhoffer, and A. E. Gib questions at their appropriate scales Gosz, J. R., ancl P. J. H. Sharpe. 1989. Broad lin. In press. Biogeochemical diversity and with appropriate tools is widely rec scale concepts for interaction of climate, element transport in a heterogeneous land ognized (Delcourt et al. 1983, Gosz topography, and biota at biome transitions. scape: the North Slope of Alaska. In M. G. and Sharpe 1989, O'Neill et al. Landscape Ecology 3: 229-243. Turner and R. H. Gardner, eds. Quantitative Grubaugh, J. W., and R. V. Anderson. 1988. Methods in Landscape Ecology. Springer 1986). In many cases, it is important Spatial and temporal variability of floodplain Verlag, New York. to examine ecosystems at different habitat: long-term changes at Pool 19, Mis Stahl, R. L., R. H. Coupe, T. E. Richards, and spatial scales. By extending the sissippi River. Am. Midi. Nat. 119: 402- P. D. Hayes. 1989. Water resources data breadth of temporal scales considered 411. Illinois water year 1988. vol. 1. Illinois ex in a sustained research program, __ . 1989. Upper Mississippi River: sea cept Illinois River Basin. US Geological Sur sonal and floodplain influences on organic vey Water-Dflta Report IL-88-1, Urbana, IL. LTER has also made it possible, in matter transport. Hydrobiologia 174: 235- Swanson, F. J., and C. T. Dyrness. 1975. Im deed essential, to examine ecosystem 244. pact of clear-cutting and road construction behavior on multiple spatial scales. Guariguata, M. R. 1989. Landslide natural dis on soil erosion by landslides in the western turbance and forest regeneration in the Lu Cascade Range, Oregon. Geology 3: 393- quillo Mountains of Puerto Rico. Mf)sters 396. Acknowledgments dissertation, University of Florida, Gains Swanson, F. J., and J. F. Franklin. 1988. The ville. Long-Term Ecological Research Program. This work was supported by National Harmon, M. E., W. K. Ferrell, and J. F. Fran EOS: Transactions of the American Geo Science Foundation grants BSR klin. 1990. Effects of carbon storage of con physical Union 69(3): 34, 36, 46. 8514325 and BSR 8508356 to An version of old-growth forests to young for Swanson, F. J., T. K. Kratz, N. Caine, and ests. Science 247: 699-701. R. G. Woodmansee. 1988. Landform effects drews LTER and BSR 8114563 and Junk, W. J., P. B. Bayley, and R. E. Sparks. on ecosystem patterns and processes. BioSci BSR 8612107 to the Illinois-Missis 1989. 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