RELEASE-2023

Three pre-determined, randomly assigned locations are selected for each sampling event at each of 10 plots distributed throughout a site; sampling locations within a plot are not re-sampled. Soil sampling occurs 1-3 times per year depending on length of growing season, with each site always sampled during the historic peak in vegetation greenness. Soil samples are collected to a maximum depth of 30 cm, with organic and mineral soils sampled separately. Soil coring devices are generally 2-2.25” diameter, although the type of device varies based on local soil types and is recorded in the data and collection protocol. In-situ soil temperature is measured, soil samples are homogenized in the field, and subsamples destined for microbial archive and/or analyses are immediately frozen on dry ice. Gravimetric soil moisture and soil pH analyses are conducted at NEON regional laboratories. Every five years, inorganic N pools (NH4+ and NO3-) are measured on fresh and field-incubated soil cores using potassium chloride (KCl) extractions during all bouts of that year. The difference in N concentration between initial and incubated samples can be used to estimate net N transformation rates, see https://github.com/NEONScience/NEON-Nitrogen-Transformations. Every five years, peak greenness subsamples are analyzed for total organic carbon and total nitrogen concentrations and stable isotopes. Instrumentation: