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.  FIU instrumentation will be located within each Domain, at i) Core wildland sites designed to anchor studies that enable the spatial scaling and answer the Grand Challenge areas, and at ii) at two Relocatable designed to assess ecologically significant (response) gradients within the domain boundaries.  FIU instrumentation will be automated with at continual (99%) temporal coverage, 24/7/365.  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.
Results/Conclusions:

The choice of measurements and measurement design have rigorously reviewed to maximize utility to the community, traced to our high-level data products, defined to enable answering our Grand Challenge questions. Challenges toward implementing this design differ from general PI driven research.  Implementation (construction and operations) is based on science and technical requirements, and a systems engineering approach.  This approach has allowed NEON to refine and manage scope, cost, and risk.  The FIU supporting infrastructure is inherently adaptable to accommodate new measurements, new research, and new technologies in the future.  The FIU is also strategically designed to uniformly reduce uncertainty in measurements across all the environmental conditions, ecosystem types and structure in North America through instrument choice, and an operational framework that combines automated system integrity checks, optimizing field technician time, data validation and publication, and the use of a robust Calibration and Validation facility.