Evaluating the continuity of NEON and AmeriFlux data streams recorded at collocated sites from tundra to subtropics

Long-term time series are essential for detecting ecological changes and predicting future trends. However, NEON datasets are < 10 y in length. Integrating new NEON data with pre-existing AmeriFlux data would provide a robust understanding of ecosystem changes over 15–25-year time scales. We evaluated how comparable NEON’s measurements are with data from pre-existing, nearby AmeriFlux sites. We place special emphasis on the eddy covariance flux measurements, using data as they are made available to the community via the AmeriFlux data portal. A case study at Bartlett, NH suggests strong agreement in meteorology and phenology and moderate agreement in half-hourly CO₂ and energy fluxes with substantial divergence in annual carbon and water flux estimates. Whether these findings generalize on other sites remains uncertain. We expanded our analysis to a dozen paired sites from tundra to subtropics.
Meteorological data shows good or fair agreement between NEON and AmeriFlux. The Bray–Curtis dissimilarity in footprint-weighted EVI and percentage of land cover types varied considerably for different paired sites. However, the agreement of fluxes was relatively poor even at sites where land cover and the EVI were highly similar across the flux footprints.
These results suggest that – in addition to distance between paired sites – seemingly minor differences in infrastructure (tower design and height) and instrument setup (particularly for flux measurements) may result in substantial differences in measured meteorological and flux data and point to large and under-appreciated uncertainties associated with the representativeness of any one tower relative to the broader landscape .