The National Ecological Observatory Network (NEON) is a national-scale research platform for assessing the impacts of climate change, land-use change, and invasive species on ecosystem structure and function. The Fundamental Instrument Unit (FIU) is a NEON science sub-system designed to integrate the ecological drivers, responses and interactions among the ecosystem-level soil-plant-aquatic-atmosphere continuum, and enable consistent sampling at the continental scale over many decades, and with consistent sampling—to act uniformly as one single integrated observatory enabling multiple scales of inference.
 
At each site, the FIU will support a large suite of terrestrial and aquatic (see neighboring STREON Poster) measurements to provide data on abiotic drivers (climate variables), biogeochemistry, ecohydrology, and air quality. The FIU focuses the measurements at the stand- to ecossytem-level.
 
NEON partitions the United States into 20 ecoclimate domains. FIU instrumentation will be located within each Domain, at i) permanent Core wildland sites designed to anchor studies that enable the spatial scaling and answer the Grand Challenge areas, and ii) at two Relocatable sites designed to assess ecologically significant (response) gradients within the domain boundaries (20 + 40 = 60 FIU sites in current definition). FIU instrumentation aims to be automated with continual (99%) temporal coverage, 24/7/365 for at least 30 years. The FIU sub-system dovetails with the other NEON sub-systems in an overall nested design covering the time and space scales, from seconds to decades, and sub-meter to continent, respectively, all contributing toward a continental-scale observatory.