The Shortgrass Steppe LTER field station consists of the headquartersarea located on 1.6 ha, a residence for the site manager, and a corral and pasture

area of 53 ha. Three buildings are located in the headquarters area: a dormitory, astorage/workshed building, and an office/laboratory building.The main SGS LTER headquarters building (214 m2) has offices, laboratories, adining/meeting room, and a kitchen. This multi-purpose building serves as the focalpoint for all activities at the site including conferences, meetings, and classes. Adjacentto the headquarters is a storage/sample processing building (134 m2) with facilitiesfor washing, drying, and storing samples. This building also serves as the workshop/garage for field station heavy equipment. The dormitory has six rooms; five capableof double occupancy and one with four beds.

The shortgrass steppe of North America comprises a mosaic of native grassland and cropland adjacent to the eastern face of the Rocky Mountain chain. Motivation for careful evaluation and

monitoring of this region at the end of the 20th century comes from twosources. First, the Great Plains contains the major wheat producing areasfor the entire continent, in addition to important grazing lands for livestock.Second, current models of atmospheric circulation indicate that climaticchange, as a result of increased greenhouse gases, will be relatively largerhere than in most other parts of temperate North America. The combinationof socio-economic importance and vulnerability of the region to bothclimatic fluctuations and climate change make it essential that we expandour understanding of long-term ecological relationships, particularlyclimate-land use-ecosystem interactions.

The Shortgrass Steppe Long Term Ecological Research (SGS LTER) program is housed in the College of Natural Resourcesat Colorado State University and is operated in close collaboration with the USDA Agricultural Research Service and the USForest Service Pawnee National Grasslands. The SGS LTER is funded primarily through a grant from the National ScienceFoundation and is part of a coordinated network of LTER sites across North America (including two sites in Antarctica). TheShortgrass Steppe LTER focuses its research on understanding the long-term processes that affect the structure and function ofshortgrass steppe ecosystems. From 1982 until 1996, the Shortgrass Steppe LTER project was focused entirely on the Central Plains Experimental Range(CPER), a 6280-ha tract of shortgrass steppe located in the piedmont of north central Colorado approximately 61 km northeastof Fort Collins (lat. 40x49’N; long.104x46’W; elevation 1650 m). In 1996, we increased the spatial extent of our LTER site toinclude both the CPER and the 78,100 ha Pawnee National Grasslands. By expanding to our newly defined site, we increase ourrealm of inference to 23 percent of the U.S. shortgrass steppe.

The Pawnee Buttes rise above the shortgrass steppe innortheast Colorado.

Full moon setting over the shortgrass steppe.

For More InformationPlease Contact

Shortgrass SteppeLong Term Ecological Research

College of Natural ResourcesColorado State UniversityFort Collins, CO 80523

Telephone: (970) 491-4996

http://sgs.cnr.colostate.edu

The Field Station at Shortgrass Steppe

hortgrassL T E R

LONG TERM

ECOLOGICAL

RESEARCH

SSteppe

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Swift fox are an important carnivore of theshortgrass steppe.

Trace gas measurement studies help tounderstand land-atmosphere interactions.

Typical soil profile of theshortgrass steppe

Paleoecology

Water and Energy Dynamics

Disturbance

The shortgrass steppe is most vulnerable to disturbancessuch as cultivation, which alter the soil system.

Work in this area is organized by the idea that two kinds ofpopulations are most important in the long-term dynamicsand sustainability of the shortgrass steppe. The first aredominant species, such as the shortgrass blue grama(Boutelouagracilis),whichoverwhelm-inglydominates thevegetation ofthe shortgrasssteppe. Thesecond typeof importantpopulations isthose thathave a largeeffect on the ecosystem because of their unique traits andnot because of their dominance. Prairie dogs (Cynomysludovicianus) and prickly pear cactus (Opuntiapolyacantha) are such species in the shortgrass steppe.

Populations and Processes

Our research in this area focuses on the key abiotic andbiotic variables that control biogeochemical dynamics,including primary productivity, nutrient cycling, andnutrient input and export, including trace gas fluxes. Thekey abiotic variables are water availability and temperature,as they vary in time and space, and soil texture as it variesacross landscapes and regions. The key biotic variables arethe presence and distribution of individual plants and thecomposition of plant communities. Continuing long-termexperiments aredesigned to assesshow precipitation,temperature,topography, andsoil texture interactto control spatialand temporalpatterns of primaryproductivity,nutrient cycling,and trace gas loss.

Biogeochemistry

Over evolutionary time scales, climatic variation has beenthe major force influencing the structure and function ofshortgrass steppe ecosystems. Buried soils, which formed inancient landscapes, contain arecord of the vegetation andclimatic conditions whichprevailed during the last 12000years. To establish vegetationand climatic histories, the stablecarbon and oxygen isotopiccomposition of organic matter,fossil plant cells, and calciumcarbonate in buried soil layers ismeasured. This information, inaddition to the size andorientation of the buried soil, itsradiocarbon age and otherattributes, reveals much aboutpre-historic climate and theearth’s response to climate change.

Water availability is the key variable controlling shortgrasssteppe ecosystem structure and function. Measurements ofprecipitation, temperature, radiation, windspeed and soil waterare part of our long≤term field sampling program. Because ofthe close link between water and energy dynamics, land usesthat influence evaporation and transpiration can have importanteffects on the shortgrass steppe. We are using the RegionalAtmospheric Modeling System (RAMS) to investigate theinfluences of land use change on mesoscale patterns ofprecipitation and other climatic variables.

Simulationanalysis is akey part ofthe synthesisactivities forthe Short-grass SteppeLTER

project. Thedevelopment of

simulation models, such asCENTURY and STEPPE, is a

continuing process in which weincorporate our knowledge into models, test them againstdata, and modify the models. Our models have been usefulfor designing experiments and for extrapolating ourunderstanding to long temporal and large spatial scales.

Geographic Information Systems (GIS) are utilized in theanalysis of spatial data. Management of GIS data andmetadata supports ongoing research projects, public accessto GIS products, and a long-term data archive.

GIS analyses at the SGS LTER range from the study ofroot dynamics (milimeter resolution) to landscapes(hundreds of meters resolution), helping researchers betterunderstand phenomena at each level.

Summer convective thundercloud

Shortgrass Steppe LTERLocated on the western edge of

the Central GreatPlains, theshortgrasssteppe uniqueamong NorthAmerican grasslandsfor the character ofits long evolutionaryhistory of grazing byloarger herbivoresand periodic drought.Over time, intenseselection by bothdrought and grazing hascreated an ecosystemcomposed of organisms that are very well adapted to both.The unique vegetation and the concentration of belowgroundbiological activity and organic matter are two distinctivefeatures of the shortgrass steppe. The low-growing blue grama(Bouteloua gracilis), contributes 60 to 80 percent of the plant

cover, biomass, and netprimary productivity.

The main plantcommunities are shortgrasssteppe, floodplain shrubland,and salt meadow. Theshortgrass steppe isdominated by shortgrasses(64%), succulents (21%),and dwarf shrubs (8%). Otherimportant plant speciesinclude: buffalo grass, plainsprickly pear, rabbitbrush,

and four-winged saltbrush.The climate of the shortgrass steppe is typical of mid-

continental semiarid regions in the temperate zone, except forthe strong rain shadow influence of the Rocky Mountainsapproximately 60 km to the west. Mean monthly temperaturesrange from -4 to 22 degrees C seasonally and annualprecipitation has averaged 322 mm over the past 51 years.Approximately 70 percent of the precipitation occurs duringthe April–September growing season.

LayeredGIS analyses

Simulation Modelingand GIS

Two key hypotheses organize SGS LTER work in the area ofdisturbance. The first is that small≤scale disturbances are themost important source of mortality for the dominant plant, bluegrama, and as such, these disturbances represent a majorinfluence on the sustainability of the shortgrass steppe. Thesecond is that the distribution of biotic components, with alarge bias towards the belowground portion of the system,leads to anecosystem witha high degreeof resistance toabovegrounddisturbancessuch as grazingor fire, but ahighvulnerability todisturbancessuch ascultivation thatdisturb the soilsystem.

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