Assessing microbial residues in soil as a potential carbon sink and moderator of carbon use efficiency

作者：Kevin M. Geyer, Jörg Schnecker, A. Stuart Grandy, Andreas Richter, Serita D. Frey · 发表于：Biogeochemistry · 年份：2020 · DOI：10.1007/s10533-020-00720-4 · 被引用次数：83 · 研究领域：Soil Carbon and Nitrogen Dynamics、Soil and Unsaturated Flow、Clay minerals and soil interactions

Abstract A longstanding assumption of glucose tracing experiments is that all glucose is microbially utilized during short incubations of ≤2 days to become microbial biomass or carbon dioxide. Carbon use efficiency (CUE) estimates have consequently ignored the formation of residues (non-living microbial products) although such materials could represent an important sink of glucose that is prone to stabilization as soil organic matter. We examined the dynamics of microbial residue formation from a short tracer experiment with frequent samplings over 72 h, and conducted a meta-analysis of previously published glucose tracing studies to assess the generality of these experimental results. Both our experiment and meta-analysis indicated 30–34% of amended glucose-C ( 13 C or 14 C) was in the form of residues within the first 6 h of substrate addition. We expand the conventional efficiency calculation to include residues in both the numerator and denominator of efficiency, thereby deriving a novel metric of the potential persistence of glucose-C in soil as living microbial biomass plus residues (‘carbon stabilization efficiency’). This new metric indicates nearly 40% of amended glucose-C persists in soil 180 days after amendment, the majority as non-biomass residues. Starting microbial biomass and clay content emerge as critical factors that positively promote such long term stabilization of labile C. Rapid residue production supports the conclusion that non-growth maintenance acti...