Full moon sets over the shortgrass steppe  photo by N. McIntyre 

Location

From 1982 until 1996, the Shortgrass Steppe (SGS) LTER was located on the Central Plains Experimental Range (CPER), a 6280-ha tract of shortgrass rangeland located in the piedmont of north central Colorado approximately 61km northeast of Fort Collins and the campus of Colorado State University (lat. 40x49'N; long.104x46'W; elevation 1650 m). The CPER is administered by the USDA, Agricultural Research Service (ARS). In 1996, we increased the spatial extent of our LTER site to include both the CPER and the Pawnee National Grasslands (PNG). The PNG represents 78,100 ha of public lands administered by the U.S. Forest Service (USFS) adjacent to the CPER, and extending 90 km to the east. The PNG is discontinuously distributed across northeastern CO because these lands are the result of acquisitions of private land beginning in the Dust Bowl era. By expanding to our newly defined site, we increase our realm of inference to 23% of the SGS ( Fig. 2.7 ; see also Fig. 5.2). 

Climate

The climate of the SGS is typical of mid-continental semiarid regions in the temperate zone except for the strong influence of the Rocky Mountains approximately 60 km to the west. Mean monthly temperatures range from -4 to 22 degrees C seasonally and have a daily average max-min range of 17 degrees C. Annual precipitation at the CPER averaged 322 mm over the past 51 years and ranged between 107 and 588 mm. Approximately 70% of the mean annual precipitation occurs during the April to September growing season. ( For further information please see Figures Historical Precipitation, Temperature/Precipitation, and Summary Climate Information : SGS climate description and summary tables and charts) 

Typical summer thundercloud 

Plains prickly pear cactus (Opuntia polyacantha)  photo by N. McIntyre 

Vegetation

The vegetation of the SGS is dominated by shortgrasses (64%), forbs (7%), succulents (21%), and half-shrubs (8%). The key species of these groups are Bouteloua gracilis and Buchloe dactyloides; Sphaeralcea coccinea; Opuntia polyacantha; and Chrysothamnus nauseosus, Gutierrezia sarothrae, and Eriogonum effusum, respectively. Average above ground net primary production is 125 g/m² and ranges from 60 to 180 g/m2 depending on available soil water. Major differences in vegetation structure occur in saltgrass meadows dominated by Distichlis stricta and Sporobolus asper, and on floodplains where the shrub Atriplex canescens is an important component.