San Joaquin Experimental Range NEON / SJER

SJER has a Mediterranean climate. Winters are cool and wet; the rainy growing season typically runs from October to April, with peak greenness in early March. Summers are hot and dry, with average temperatures between 24-27°C (75-80°F), and high temperatures frequently exceeding 38°C (100°F). Vegetation is mostly dormant during the summer months. Mean annual temperature is 16.4°C (61.5°F). Mean annual precipitation is 539.62 mm (21.25 in.). [1] [11]

The geology of SJER is granodiorite and quartz monzonite. [5]

At SJER parent materials consist of residuum, colluvium, and local alluvium that are derived from Mesozoic aged granite, quartz monzonite, granodiorite, and quartz diorite crystalline rocks. The primary soil series on the site are Ahwahnee (Coarse-loamy, mixed, active, thermic Mollic Haploxeralfs) and Vista (Coarse-loamy, mixed, superactive, thermic Typic Haploxerepts). Both soils are moderately deep to a paralithic contact. [4]

SJER is primarily open oak woodland, with an overstory of evergreen oaks, gray pine, scattered manzanita and whitethorn shrubs. The understory is cool season grasses (predominantly Bromus) with other perennial forbes and legumes. Native bunch grasses can be found on some northern slopes. [1] [3]

A large population of California ground squirrels (Spermophilus beecheyi) and other small rodents supports abundant mesocarnivores, including coyotes (Canis latrans), American badgers (Taxidea taxus), and bobcats (Lynx rufus), as well as gopher snakes and rattlesnakes. The site hosts a wide variety of resident and migratory songbird and raptor species, including the important game species California quail (Callipepla californica). Species unique to the region include the Western spadefoot toad (Spea hammondii), San Joaquin pocket mouse (Perognathus inoratus), and Heerman's kangaroo rat (Dipodomys heermani). [3]

The San Joaquin Experimental range was established in 1934 as California's first range research station. Its original research goal was to identify cost-effective methods of livestock production and monitor its effect on the annual grass and oak woodland ecosystem. Research objectives have since expanded to contribute to scientific knowledge of ecological patterns and processes in this ecosystem. In 2009, the Southern Sierra Critical Zone Observatory established an eddy-covariance flux tower on the site to monitor meteorological processes along the critical zone elevation gradient.

The period between 2011 and 2015 marked the driest years on record in California, and significantly reduced the flow of the San Joaquin river. Multiple small wildfires have affected the site and its surroundings in recent years. [2] [6] [7] [8] [9]

SJER is currently managed in collaboration by the Pacific Southwest Research station of the United States Forest Service and California State University at Fresno's Agricultural foundation. It hosts the university's commercial cow-calf herd. The range serves as an outdoor lab for agriculture students at Fresno State and Fresno City College and is used for extensive ecological and agricultural research. Data collected at San Joaquin forms the basis for over 500 scientific publications in disciplines ranging from livestock production to nutrient flow modeling and fire ecology.

The area immediately surrounding SJER is agricultural, primarily cattle pasture with some wine and fruit production. The site is situated relatively close to two urban areas: the city of Fresno, 32 km (20 mi.) south, and Coarsegold/Oakhurst, 24 km (15 mi.) north. [10]

NEON plot establishment at SJER began in 2015, and was completed in 2016. The site transitioned to operations in October 2016. The terrestrial sampling and observations began in the same month, coinciding with the start of the central valley’s cool, rainy growing season. Construction of the site’s 39 m (127 ft.), 6-level instrumentation tower was completed in 2017, and the tower came online and began streaming data in the fall of 2018.