Optimization of the National Ecological Observatory Network root sampling design

The design of the National Ecological Observatory Network (NEON) was informed by literature review, consultation with subject matter experts, and analysis of prototype data collection efforts. To ensure long-term scientific validity and resource efficiency, we analyzed multiple years of continental-scale NEON data collected according to the initial design to determine whether it was possible to fine-tune the time-intensive root sampling protocol to optimize resources while still meeting initial design requirements. We focused our analyses on field sampling (since the number of cores collected has a significant impact on time-intensive laboratory sorting) and laboratory dilution sampling for fine root fragments. Using bootstrapping and power analysis methods we determined that there were 8 (out of 47) terrestrial sites where we could reduce within-plot replication in field sampling and still detect change in fine root biomass in a pooled 0–2 mm size category, and we implemented this in early 2025. Furthermore, we used a combination of bootstrapping and temporal change analysis methods to determine that lab subsampling procedures to estimate fine root fragment biomass could be reduced from 10 to 3 subsample replicates at all 47 terrestrial NEON sites without adversely impacting the ability to estimate total fine root biomass, and we implemented this change in early 2024. In combination, these analyses allowed us to reduce labor requirements for two components of the NEON root sampling protocol while still delivering high quality open-source data available to all users at https://data.neonscience.org/data-products/DP1.10067.001 .