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NEON quantifies soil microbe biomass () via measurement of phospholipid fatty acids (PLFA). In order to account for differences across samples in the effectiveness of lipid extraction, the high-throughput PLFA method employed (Buyer and Sasser, 2012) specifies that a known quantity of an internal standard be added to each sample. Calculated lipid concentrations are then scaled by the recovery or extraction efficiency of that internal standard. Prior to November 1, 2021, NEON microbial biomass data were reported in unscaled format, with extraction efficiency provided and the expectation that end users perform scaling corrections themselves.

When NEON switched PLFA analytical laboratories in 2022, it became clear that reporting unscaled concentrations is difficult when using the Sherlock analysis system commonly leveraged for high-throughput PLFA, as it is designed to take the scaling into account. Since the community best practice is to use scaled data, NEON stopped ingesting unscaled data for samples collected after November 1, 2021 and began to ingest scaled data instead into a new sme_scaledMicrobialBiomass table. These newer records do not report extraction efficiency, but they do provide recovery of the internal standard (in raw GC units) for each sample, as well as in standards and blanks in the sme_batchResults table. Soil samples collected prior to November 1, 2021 that meet a minimum extraction efficiency (33%) have been corrected for extraction efficiency and are presented in the sme_scaledMicrobialBiomass table. Records created after November 1, 2021 will not appear in the original, unscaled sme_microbialBiomass table.

Please use the Contact Us form for further inquiries; please select DP1.10104.001 in the Data Product dropdown list and include the term "PLFA Scaled Table" in the body of your request.

References:

Buyer, J.S. and M. Sasser. 2012. High throughput phospholipid fatty acid analysis of soils. Applied Soil Ecology 61:127�130.