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North Sterling (STER) is a terrestrial NEON field site located in Logan County in northeast Colorado. It has an sampling area of 3.2 km² (791 acres) and sits at about 1350 m (4429 ft.) elevation. STER is an agriculture site on privately owned land. Various crops are grown across the site, including winter wheat, millet, and maize. The North Sterling site was selected to represent agricultural land and practices in eastern Colorado. The site is part of NEON’s Central Plains Domain (D10), along with two other terrestrial sites and one aquatic site. STER is not colocated with an aquatic field site. [1]

The Central Plains region is known for dry, hot summers and cold winters. Weather can change drastically in a short period of time. The combination of high elevation and mountain ranges mainly drives this region’s climate. Mean annual temperature at the site is 9.7°�� (49.5°F) and the mean annual precipitation is 432.7 mm (17 in.). The area can be subject to tornados, flooding, blizzards, and severe winter storms. [8] [11]

The geology at this site is characteristic of the Ogallala Formation which is comprised of alternating conglomerates and sandstones. [12]

Soils at the STER site originate from aeolian deposits, loess, recent alluvium, and Tertiary aged alluvium. The major components of soils are from several different pedon types: Colby, Kuma, Platner, Rago, Sampson, Stoneham, Wages, and Weld. [2]

There are no major aquatic systems within the site boundary. Concentrated precipitation events can lead to flooding in the region. Snow cover does not last long due to the abundance of sunlight. [7]

Cropping systems under no-till management were initiated in 1985 at the STER location. Possible crops include winter wheat, winter wheat-maize, millet, maize, sorghum, triticale, forage millet, and sunflower. Over 85% of the sampling area is cultivated crops, with the rest being classified as grassland herbaceous or developed open space. However, under the current Land Use Agreement, sampling only occurs in the space for cultivated crops. Over 60 distinct plant species have been identified within the sampling area. [1] [10]

Even though the field site is within agricultural lands, many of the typical fauna species of the region are observed. Large mammals such as mule deer (Odocoileus hemionus), pronghorn (Antilocapra americana), and coyote (Canis latrans) can be found nearby and in the greater central plains region. Fauna data are captured in various NEON protocols, including data on ground beetles, small mammals, and birds. More than 60 different taxa from the Carabidae family have been identified so far at STER. 13 distinct small mammals have been observed within the site, with North American deermice (Peromyscus maniculatus), Northern grasshopper mice (Onychomys leucogaster), and hispid pocket mice (Chaetodipus hispidus) as the most common species observed. NEON has observed over 40 species of birds, with typical Central Plains grassland birds such as western meadowlark (Sturnella neglecta), horned lark (Eremophila alpestris), and lark bunting (Calamospiza melanocorys) in greatest abundance. [4] [5] [6] [7]

Before establishment of the no-till cropping system, the site was under conventional tillage since it was taken from native sod in about 1910. Conventional tillage from 1910 to 1985 ranged from moldboard plowing to sweep tillage in the later years. Substantial lithic scatters show that the region was once inhabited by indigenous peoples. Around 1000AD, a culture archaeologists call "Upper Republican" lived in the upper Republican River area in northeast Colorado and surrounding states. Cheyenne, Arapaho, and Pawnee tribes inhabited the region prior to the arrival of French fur trappers in the 1700s who came via the Southern Platte River. [1] [7]

The site is at the edge of a non-tilled experimental field that is used for the long term sustainable Dryland Agroecosystems Project (DAP), which was initiated in 1985 at three sites in eastern Colorado (Sterling, Stratton, and Walsh) to evaluate the effects of cropping intensity on production, water use efficiency, and selected soil chemical and physical properties. The DAP site was established in 1985 and was chosen because of representative soils present. The primary crop is winter wheat grown in a wheat-fallow rotation. [1]

Instrumentation systems went online and began producing preliminary data in November 2013. STER was reviewed for sampling readiness in March 2014, and plot establishment began in October 2014. Dry runs of observational sampling began later in October 2014. Instrumentation construction was fully completed in April 2017.