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For the Root biomass and chemistry, periodic () protocol, we reduced the number of dilution subsamples per root core in table bbc_dilution from 10 to 3 at all terrestrial sites. 

This decision was based on analyses that are congruent with the framework for NEON's Observational Sampling Design Optimization. More specifically, we analyzed the biomass of fine root fragments quantified via the dilution sampling technique, reported in the bbc_dilution table, to determine whether the number of dilution subsamples could be reduced while maintaining the ability to adequately estimate fine root fragment mass. The current dilution sampling effort requires n=10 dilution subsamples per core, and we used subsampling with replacement to evaluate whether fewer dilution subsamples could generate a mean estimated fragment mass within ± 10% of the mean obtained with n=10 dilution subsamples (with 90% confidence). Because fragment mass is only useful within the context of total fine root biomass summed across the sorted size categories, published in the bbc_rootmass table, we also investigated whether fewer dilution subsamples per core could generate mean total fine root biomass (fragments + sorted roots) within ± 10% of mean total fine root biomass. Subsampling analyses (n=1000 iterations) indicated that dilution subsampling can be reduced from n=10 to n=3 replicates, and total fine root biomass estimates are unchanged (means derived with n=3 dilution subsamples were within ± 10% of the mean calculated with n=10 dilution subsamples with 90% confidence). This change was reviewed and approved by the NEON Plant Biomass and Productivity Technical Working Group, and was implemented on 2023-08-02, saving 70% of the labor associated with time-intensive sorting of dilution subsamples. 

Please use the Contact Us form for further inquiries regarding this change, and include the term "RITM0057114" in the body of your request.