Delta Junction NEON / DEJU

Delta Junction (DEJU) is a terrestrial NEON field site located in central Alaska, approximately 150 km (93 mi.) southeast of Fairbanks and 15 km (9 mi.) south of the community of Delta Junction. The 29.9 km² (7390 acre) site is managed by the U.S. Bureau of Land Management. It sits within the Tanana Valley at an elevation of 440 - 485 m (1400 - 1600 ft.), 30 km (18 mi.) from the confluence of the Tanana and Delta Rivers. The location is bordered to the north by the White Mountains, to the southeast by the Granite Mountains, and to the southwest by the Alaska Range. DEJU is one of the four sites (three terrestrial and one aquatic) located in the NEON Taiga Domain (D19), which comprises Alaska’s interior and the Alaska Peninsula. [1]

This region’s climate is subarctic, characterized by long, cold winters and brief, mild summers. Delta Junction receives an average of only 305 mm (12 in.) of annual precipitation, three-quarters of which falls between May and September. As expected, temperatures are relatively low throughout the year, with an average annual temperature of -3°C (26.6°F), and average temperature highs staying below freezing from October to March. Temperature extremes are recorded from -52.7°C to 33.3°C (-63°F to 92°F). Due to its subarctic latitude, Delta Junction experiences no night (only twilight) from May to July, and only four to five daylight hours between November and January. [1] [2] [5] [6]

Local geology is typical of a glaciofluvial setting, where the dominant material is well-rounded gravel in a matrix of silt and sand. Geomorphological features include outwash plains, moraines, stream terraces and floodplains, all of which are characteristic of a formerly glaciated river valley. [2] [3] [4]

Soils at DEJU are typically eluvial deposits formed by weathering of the underlying parent material, which consists of gravelly glacial till and outwash covered by a thin layer of loess. Organic horizons vary in thickness across the site, with low, wet, frozen areas overlain by thick (>20 cm) organic deposits. The soil is subgelic (-4°C - 0°C/25°F - 32°F) with discontinuous permafrost, and there is evidence of cryoturbation in areas. [4]

Delta Junction sits near the glacially-fed Tenana River, which drains the north slope of the Alaska Range. [1] [5]

The predominant vegetation at Delta Junction is scrubby evergreen forest, where stunted trees like black spruce (Picea mariana), white spruce (Picea glauca) and American dwarf birch (Betula glandulosa, Betula nana) dominate the canopy. Vegetation at the site varies with differences in elevation and drainage; well-drained, upland zones feature quaking aspens (Populus tremuloides) and white spruce, while areas with poor drainage host sedges, mosses, and low-growing shrubs like lingonberry (Vaccinium vitis-idaea), crowberry (Empetrum nigrum), bog blueberry (Vaccinium uliginosum), bog Labrador tea (Ledum palustre), false toadflax (Geocaulon lividum), and bearberry (Arctostaphylos uva-ursi). [1] [7]

Animals native to central Alaska and the Tenana Valley include coyote (Canis latrans), red fox (Vulpes vulpes), moose (Alces alces), lynx (Lynx canadensis), and gray wolf (Canis lupis). This area also falls within the range of wood bison (Bison bison athabascae), a northern subspecies of American bison identified as threatened under the Endangered Species Act. The small mammal species studied at DEJU include North American brown lemming (Lemmus trimucronatus), several vole species in the Microtus genus, northern red-backed vole (Myodes rutilus), northern bog lemming (Synaptomys borealis), and meadow jumping mouse (Zapus hudsonius). [8] [9] [10]

The earliest direct evidence of humans in Alaska is found in the Tanana River valley near Delta Junction, in the form of butchered animal bone and charcoal dating to roughly 14,000 years ago. Meanwhile, the earliest human remains in the valley date to 11,500 years ago, a period of rising temperatures, rising sea levels, and the gradual inundation of the Ice Free Corridor from Siberia at the end of the Pleistocene and the beginning of the Holocene (the geologic epoch which we are in today). Humans continued to occupy the valley (and, more broadly, central Alaska) throughout the Holocene, providing a constant in a region which saw dramatic changes in climate, alterations in vegetation structure and fauna, large flood events, and fluctuations in wildfire regimes. Russian contact (and, subsequently, colonization) in Alaska began in the 18th century, beginning a period of resource exploitation, fur-based trade economy, and conflict with indigenous populations. In 1867, Alaska was incorporated into the U.S. as the Department of Alaska. Non-native settlement near Delta Junction began with the construction of a roadhouse and, later, a telegraph station near the confluence of the Delta and Tanana Rivers along the Valdez-Fairbanks Trail (later the Richardson Highway) which connected Fairbanks to the coast.

In 1942, Fort Greely (currently an active U.S. military base) was established in an area including what is now DEJU, introducing a source of direct anthropogenic disturbance to the landscape. Recent disturbance history at the site includes forest fires, permafrost degradation, and the construction of roads (including the Richardson Highway), trails, and structures at Fort Greely. Ecological land surveys were performed at Fort Greely and adjacent BLM land in the early 2000s to assess the impacts of these human-mediated disturbances. [11] [12] [13] [14] [15] [16] [17] [18] [19] [20]

DEJU is located on land managed by BLM Alaska and surrounded by Fort Greely, an active U.S. military base. BLM Alaska manages 280,000 km² (108,000 sq. mi.) of surface land and 890,000 km² (344,000 sq. mi.) of subsurface land (mineral estate), comprising approximately 30% of federal public land in the state. The site is within the major land resource area (MLRA) 228, where the primary form of land use is remote wildland recreation (subsistence hunting, backcountry hiking, mountaineering, etc.) and many regions are actively logged. Fort Greely is a 2676 km² (1033 sq. mi.) military base used for cold-weather training and is part of the Ballistic Missile Defense System. [1] [5] [19] [21] [22] [23]

Plot establishment at DEJU began in 2015, and the site was reviewed for sampling readiness in 2016. Dry runs of observational sampling began in late 2016, followed by the first publications of data products for most observational protocols. Instrumentation systems went online and began producing data in 2017.