Liu et al. (2025) A tale of two towers: comparing NEON and AmeriFlux data streams at Bartlett Experimental Forest

Identification

• Journal: Agricultural and Forest Meteorology
• Year: 2025
• Date: 2025-12-28
• Authors: Yujie Liu, Paul C. Stoy, Housen Chu, Dave Hollinger, Scott V. Ollinger, Andrew P. Ouimette, David Durden, Cove Sturtevant, Ben Lucas, Andrew D. Richardson
• DOI: 10.1016/j.agrformet.2025.110939

Research Groups

• Northern Arizona University, Center for Ecosystem Science and Society (ECOSS), Flagstaff, AZ, USA
• Department of Biological Systems Engineering, University of Wisconsin – Madison, Madison, WI, USA
• Climate & Ecosystem Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
• U.S. Department of Agriculture, Forest Service, Northern Research Station, Durham, NH, USA
• Earth Systems Research Center, University of New Hampshire, Durham, NH, USA
• National Ecological Observatory Network, Battelle, Boulder, CO, USA
• Northern Arizona University, Department of Mathematics and Statistics, Flagstaff, AZ, USA
• Northern Arizona University, School of Informatics, Computing & Cyber Systems (SICCS), Flagstaff, AZ, USA

Short Summary

This study compared parallel meteorological, phenological, and eddy covariance flux observations from co-located AmeriFlux and NEON towers at Bartlett Experimental Forest, finding excellent agreement for meteorology and phenology but significant annual-scale discrepancies in carbon dioxide and latent heat fluxes, highlighting challenges in merging long-term data from different platforms.

Objective

• To evaluate the agreement of parallel observations from AmeriFlux and NEON towers for standard meteorological variables, CO2, sensible heat, and latent heat fluxes, and phenology.
• To identify potential causes for observed disagreements, particularly in annual carbon balance, and discuss implications for long-term ecological monitoring and carbon accounting.

Study Configuration

• Spatial Scale: Bartlett Experimental Forest, New Hampshire, USA. Two towers separated by a horizontal distance of 93 meters.
• Temporal Scale: Multi-year comparison of parallel observations, with analysis conducted at half-hourly and annual scales.

Methodology and Data

• Measurement techniques used: Eddy covariance (for CO2, sensible heat, and latent heat fluxes), PhenoCam imagery (for phenology).
• Data sources: AmeriFlux tower data, NEON tower data, PhenoCam imagery.

Main Results

• Excellent agreement was observed between AmeriFlux and NEON for standard meteorological variables and phenology.
• Good agreement was found for CO2, sensible heat, and latent heat fluxes at the half-hourly scale.
• Large disagreements in CO2 and latent heat fluxes occurred at the annual scale.
• The AmeriFlux tower measurements indicated a site close to carbon-neutral (-8 ± 65 g C m⁻² y⁻¹, mean ± 1 standard deviation).
• The NEON tower measurements indicated the forest as a carbon sink (-137 ± 10 g C m⁻² y⁻¹, mean ± 1 standard deviation).
• Potential causes for disagreement include differences in measurement height (26 m for AmeriFlux vs. 35 m for NEON), leading to different flux footprints, and differences in the flux measurement systems.

Contributions

• Provides a rare site-level replication study comparing data streams from two major long-term ecological observation networks (AmeriFlux and NEON).
• Highlights that while meteorological and phenological data may show strong agreement, annual carbon and energy fluxes can diverge significantly between different measurement platforms.
• Emphasizes the critical need for caution when attempting to merge long-term flux data from different measurement platforms due to potential biases in annual sums.
• Underscores the implications of platform-specific differences for carbon accounting and the assessment of natural climate solutions.

Funding

Not specified in the provided text.

Citation

@article{Liu2025tale,
  author = {Liu, Yujie and Stoy, Paul C. and Chu, Housen and Hollinger, Dave and Ollinger, Scott V. and Ouimette, Andrew P. and Durden, David and Sturtevant, Cove and Lucas, Ben and Richardson, Andrew D.},
  title = {A tale of two towers: comparing NEON and AmeriFlux data streams at Bartlett Experimental Forest},
  journal = {Agricultural and Forest Meteorology},
  year = {2025},
  doi = {10.1016/j.agrformet.2025.110939},
  url = {https://doi.org/10.1016/j.agrformet.2025.110939}
}