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Glycine mineralization in situ closely correlates with soil carbon availability across six North American forest ecosystems

TitleGlycine mineralization in situ closely correlates with soil carbon availability across six North American forest ecosystems
Publication TypeJournal Article
Year of Publication2010
AuthorsMcFarland, JW, Ruess, RW, Kielland, K, Pregitzer, K, Hendrick, R
JournalBiogeochemistry
Abstract

Free amino acids (FAA) constitute asignificant fraction of dissolved organic nitrogen (N)in forest soils and play an important role in the Ncycle of these ecosystems. However, comparativelylittle attention has been given to their role as labilecarbon (C) substrates that might influence themetabolic status of resident microbial populations.We hypothesized that the residence time of simpleC substrates, such as FAA, are mechanisticallylinked to the turnover of endogenous soil C pools.We tested this hypothesis across a latitudinalgradient of forested ecosystems that differ sharplywith regard to climate, overstory taxon, and edaphicproperties. Using a combined laboratory and fieldapproach, we compared the turnover of isotopicallylabeled glycine in situ to the turnover of mineralizablesoil C (Cmin) at each site. The turnover ofglycine was rapid (residence times{\backslash}2 h) regardlessof soil type. However, across all ecosystems glycineturnover rates were strongly correlated with indicesof soil organic matter quality. For example, C:Nratios for the upper soil horizons explained *80%of the variability observed in glycine turnover, andthere was a strong positive correlation between insitu glycine-C turnover and Cmin measured in thelaboratory. The turnover of glycine in situ wasbetter explained by changes in soil C availabilitythan cross-ecosystem variation in soil temperature orconcentrations of dissolved inorganic N and FAA-N.This suggests the consumption of these low-molecular-weight substrates by soil microorganisms maybe governed as much by the overall decomposabilityof soil C as by N limitation to microbial growth.

DOI10.1007/s10533-009-9400-2