Long Term Ecological Research

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vada, CO 80003 (telephone 303-425-5610).

The Long-TermEcologicalResearchProgramFrederick J. Swanson andJerry F. Franklin

Major developments have emerged in thefield of ecology as a result of taking a long-term approach to both basic and applied re-search [Strayer, 1986]. In recognition of boththe advantages of long-term research pro-grams and the historical difficulty of sustain-ing such research efforts, the National Sci-ence Foundation (NSF) instituted its Long-Term Ecological Research (LTER) Programin 1980 [Callahan, 1984). The LTER Programhas a number of important links with thegeosciences and is likely to play a significantrole in work on terrestrial, freshwater, andestuarine ecosystems within the InternationalGeosphere-Biosphere Program (IBGP); it isthus a good time for us to begin communicat-ing with geoscientists who are helping toshape IGBP.

LTER SitesThe LTER Program began in 1980 with

the funding of six sites, a number that hasnow grown to 15 (Table 1 and Figure 1). Ananticipated 1988 grant competition may bringthe network to 20 sites. The existing sitesspan a great array of terrestrial and aquaticecosystems — desert, prairie, tundra, forest,small stream, big river, lake, and estuary.Common threads among these diverse ecosys-tem research sites include

established research sites with long-termrecords of environmental and biologicalvariables (assurance of continued securityand availability of sites for research arecritical for their selection; in many cases,LTER sites contain areas of relatively pris-tine, preserved ecosystems, as well as areaswhere large-scale manipulative experimen-tation is possible),established interdisciplinary teams of re-searchers with stable leadership and institu-tional support,programs of research in five core areas (de-scribed below), anda commitment to work with other sites inthe LTER network.

These research and administrative responsi-bilities are supported in part by modest funds(about $365,00C per site per year) providedthrough NSF's LTER grants program.

The field sites not only serve the LTER ef-forts but are intended to attract cooperatorsand allied research programs. Extensiveknowledge of site conditions and historiesmake the sites ideal locations for large-scalefield experimentation dealing with issues ofglobal change. As an example, a lake acidifi-cation project involving multiple institutions(U.S. Environmental Protection Agency, Du-luth; University of Wisconsin, Madison; Uni-versity of Wisconsin, Superior; U.S. Geologi-cal Survey; University of Minnesota, Minne-apolis; University of Minnesota, St. Paul;Wisconsin Department of Natural Resources)has been established at the Northern LakesLTER site and forms a natural complementto and extension of the LTER research.

Another example of large-scale, multidis-ciplinary research at an LTER site is FIFE(First ISLSCP Field Experiment, where1SLSCP is the International Satellite LandSurface Climatology Project). sponsored bythe National Aeronautics and Space Adminis-tration (NASA) and currently underway atthe Konza Prairie LTER site. Contemporane-ous ground-based field studies of the KonzaPrairie LTER program provide ground truthfor a tremendous array of remotely senseddata. This NASA–LTER interaction sets thestage for important advances in the use of

ecological modeling and innovative technolo-gies for measuring and integrating large-scale(landscape, regional, global) spatial variationin ecological processes.

LTER ResearchThe core areas of LTER research arepattern and control of primary . production,spatial and temporal distribution of popula-tions selected to represent trophic struc-ture,pattern and control of organic matter accu-mulation in soil and sediment,patterns of biogeochemical cycling throughsoil, groundwater, and surface water, andpatterns and frequency of disturbances,both natural and human induced.

Despite common work in these core areas,the research programs at individual sites arequite distinctive, responding to local environ-ments, interests of researchers, and historiesof site management and research.

Temporal ScalesThe long-term aspect of LTER research

takes many forms. Long-term direct experi-

ments involving disturbance by fire, grazing,and manipulation of nutrients, pollutants,and water are the centerpieces of research atmost sites. Retrospective studies, based on thetechniques of paleolimnology, paleopedology,and dendrochronology, are used at severalsites to place the course of ecosystem changeand disturbances in a historical context.Chronosequence techniques, which involvethe substitution of space for time, are em-ployed at sites with long-lived dominant spe-cies (such as the forests of the Pacific North-west, where conifers may attain ages of over1000 years). Maintenance of long-term rec-ords of physical and biological characteristicsof upland and fluvial environments providean opportunity to measure the effect of natu-ral disturbances. For example, the compara-tive impact of a severe drought in 1986 on anAppalachian forest and on a coastal estua-rine-forest landscape is being assessed by ainterste study. Modeling of ecosystem func-tion, based on process-level studies and con-strained by results of retrospective work, areused to predict future ecosystem behavior.Many sites combine these techniques, if ap-propriate to the ecosystem.

TABLE I. LTER Sites, Environments, Institutions, and Major Topics of Research

Site Environment Institutions Major Research Themes

Biogeochemical cycling, soil, andvegetation patterns in relation tolandforms

Forest-stream interactions,disturbances, forest dynamics, logdecomposition

Ecosystem response to fire and• fluvial disturbanceEffects of nutrients, fire, herbivores,

and other disturbance on primaryproduction, succession, and soilprocesses; dynamics of theprairie-forest ecotone

Effects of erosion, hydrology,landforms, herbivores on soil andvegetation properties;biogeochemical cycling

Land-stream interactions, ecosystemresponse to disturbance,biogeochemical cycling

Biogeochemical cycling, ecosystemresponse to disturbance

Sediment and biogeochemialcycling, floodplain-riverinteractions

Ecosystem response to erosion andmanipulation of water andnutrient availability

Ecological constraints on agronomicproductivity; impact ofagriculture on the largerlandscape; biogeochemical cycling

Roles of fire, grazing, precipitationin ecosystem

Effects of climate, water, soil onsediment movement andbiogeochemical cycling;paleoecology

Biogeochemical and sedimentcycling

Precipitation, groundwater,geochemical, landform influenceson lake ecosystems

Island-marsh-estuarine interactions,landform response to sea levelrise, primary and secondarysuccession, island ecology andbiology

Central Plains Experimental shortgrass, steppeRange

Coweeta Hydrologic Laboratory forest, stream

Hubbard Brook Experimental forest, streamForest

Illinois-Mississippi Rivers river, forest

Jornada Experiment Range shrub- and grassland

Kellogg Biological Station agricultural ecosystems

Colorado State University,USDA AgriculturalResearch Service

University of Georgia,USDA Forest Service

Cornell University, SyracuseUniversity, USDA ForestService

Illinois Natural History,Water, and Geologicalsurveys, Western IllinoisUniversity

New Mexico State University

Michigan State University

Konza Prairie Research Natural tallgrass prairie, stream, forest Kansas State University

AreaNiwot Ridge—Green Lakes Valley tundra, forest, lakes, stream University of Colorado

North Inlet (Hobcaw Barony)

forest, stream, salt marsh, estuary University of South Carolina

Northern Lakes (Trout Lake lakes, forest University of Wisconsin—Biological Station) Madison

Virginia Coast Reserve estuary, barrier island, nearshore University of Virginiamarine

Alaska Arctic tundra

H. J. Andrews Experimental

forest, streamForest

Bonanza Creek

forest river

Cedar Creek Natural History prairie, forest, lake, bogArea

Woods Hole OceanographicInstitute

Oregon State University,USDA Forest Service

University of Alaska, USDAForest Service

University of Minnesota

Spatial ScalesAlthough the initial emphasis of LTER was

the time dimension, issues of global changeand a growing interest among ecologists inlandscape-scale phenomena have pushed theresearch to larger spatial dimensions as well.Much traditional research in terrestrial, estu-arine, and freshwater ecology has been car-ried out at the scales of plots (square meter tohectare), stream reaches, and individuallakes. However, several LTER projects havedesigned their research programs within thecontext of hierarchy of spatial scales, incl d-ing the soil particle, landscape, and globe[French, 1986; Woodmansee and Adanuen,19831.

A crucial scale of research is the landscape,encompassing many hectares and multiplepatches of vegetation, stream reaches, orlakes. Several LTER projects are examiningbiological properties of ecosystems in relationto landforms and position within the land-scape [Swanson et a!., 1988]. Examples includepatterns of soil and vegetation along topo-graphic sequences from ridge top to valleyfloor or playa, interactions between riversand adjacent forests as controlled by land-forms, the biogeochemistry of lakes in rela-tion to location within their drainage basins,and the effect of sea level rise on terrestrialnutrient flux.

To move to the regional scale, severalLTER groups are using networks of satellitefield sites, modeling efforts, and remote sens-ing to examine regional patterns of primaryproductivity and other biological processes inrelation to climate [Dyer and Crossley, 1986;Sala et al., 19881.

These are all important steps in under-standing the links among plot, landscape, re-gional, continental, and global scales of eco-system function.

LTER Network

Although LTER sites are selected on thebasis of peer evaluation of the quality of re-search proposed at the individual sites, thecollection of LTER sites is developing into anintegrated network. The substantial effortthat goes into intersite activities is lead by acoordinating committee consisting of princi-pal investigators from all sites, a chairman,

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and an NSF representative. Workshops areheld to further collaborative research and toshare ideas and techniques. Common stan-dards for meteorological monitoring [Green-land, 1986] and data management [Michener,1986] have been established. Joint researchand exchange of scientists among sites areused for comparative studies and to testhypotheses in a variety of environments.

LTER and IGBP

The LTER Program will contribute sub-stantially to the terrestrial, freshwater, and es-tuarine biology phases of IGBP in view ofcharacteristics of the field sites, research pro-grams, and LTER network as a whole. LTERsites are obvious "biosphere observatories"[National Research Council, 1986] because oftheir long direct and surrogate records of en-vironmental variables, structure, and compo-

sition of biological communities, and biogeo-chemical processes. These long-term recordsare a distinctive contribution of terrestrialbiosphere observatories to assessing globalchange; they stand in contrast to satellite andoceanographic observation platforms thattypically record snapshots in time. Further-more, the research infrastructures and high-quality physical environments at biosphereobservatory sites suit them ideally for furthercooperative large-scale research efforts.

LTER sites are well-suited for examiningquestions about how ecosystems respond tostress. Many of the LTER sites have long-term field experiments underway that dealwith system stability and productivity. Effectsof changes in climate or pollution load maybe detected within and predicted from thesefield experiments.

Modeling of biological interactions with at-mospheric variables at landscape and regionalscales can yield predictions of the response ofecosystems, such as the response of agro-eco-systems and rangelands of the Great Plains toclimate change. Moreover, such models couldalso encompass effects of the biota on thephysical environment, including the atmo-sphere.

Maintenance of biological diversity at local,regional, and broader scales is an importantissue within the scope of IGBP [National Re-search Council, 1986]. Portions of most LTERsites are reserved natural ecosystems and thusserve as refuges for species and genotypesthreatened by land uses such as forestry,grazing, agriculture, and suburbanization.Collections of organisms and species lists doc-ument diversity at these sites, providing thepotential to record change in diversity in re-sponse to global and local changes in theenvironment. Several sites have long-term ex-periments designed to determine how variousenvironmental factors control local diversity.

The LTER network of research programsis a prototype in several respects of the typeof cooperative research that would be re-quired within a large-scale, interdisciplinaryenterprise such as IGBP. LTER's most impor-tant contribution to IGBP probably will bethe existence of a large, cooperating group ofecosystem scientists with broad perspectiveson how the terrestrial biosphere interactswith the atmosphere and oceans. Thesebroad perspectives are an outgrowth of thediversity of disciplines and environmentsfrom which these scientists come.

For more information about the LTERprogram, contact Judy Brenneman, ForestrySciences Laboratory, 3200 Jefferson Way,Corvallis, OR 97331 (telephone: 503-757-4340). The LTER Program also publishes the"LTER Newsletter," which contains informa-tion on research activities.

References

Callahan, J. T., Long-term ecological re-search, BioScience, 34, 363, 1984.

Dyer, M. 1., and D. A. Crossley, Jr. (Eds.),Coupling of ecological studies with remotesensing, U.S. Dept. Slate Publ. 9504, Wash-ington, D.C., 1986.

Greenland, D., Standardized meteorologicalmeasurements for long-term ecological re-search sites, Bull. Ecol. Suc. Am., 67, 275,1986.

Michener, W. K. (Ed.), Data Mangernent in theEcological Sciences, Belle W. Baruch LibraryMar. Sci. Sci., vol. 16, University of SouthCarolina Press, Columbia, S.C., 1986.

National Research Council, Global Change inthe Geosphere-Biosphe re: Initial Priorities for anIGBP, National Academy Press, Washing-ton, D.C., 1986.

Sala, 0. E., W. J. Parton, L. A. Joyce, and W.K. Lauenroth, Primary production of thecentral grassland region of the UnitedStates: spatial pattern and major comm ols,Ecology, in press, 1988.

Strayer, D., An essay on long-tern) ecologicalstudies, Bull. Ecol. Soc. Am., 64, 271, 1986.

Swanson, F. j., T. K. Kratz, N. Caine, and R.G. Woodmansee, Landlorm effects On eco-systems, BioScierice, in press, 1988.

Woodmansee, R. G. and F. J. Adamsett, Bio-geochemical cycles and ecological hierar-chies, in Nutrient Cycling in AgriculturalEcosystems, College Agric. Exp. Stn. Spec.Publ. 23, Univ. of Georgia, Athens, 1983.

Frederick J. Swanson is with the U.S. Depart-ment of Agriculture . Forest Service, Pacific North-west Research Station, Corvallis, Oreg., and also

with the H. J. Andrews LTER Site, Blue River,

Oreg. J. F. Franklin is with the Pacific NorthwestResearch Station, Forestry Sciences Laboratory,Corvallis, and with the University of Washington,Seattle. He is also the chairman of the LTER Net-