Pathways of mineral‐associated soil organic matter formation: Integrating the role of plant carbon source, chemistry, and point of entry
By N. Sokol, Jonathan Sanderman, M. Bradford. Global Change Biology, 2018
699 citations recorded by the source corpus.
To predict the behavior of the terrestrial carbon cycle, it is critical to understand the source, formation pathway, and chemical composition of soil organic matter (SOM). There is emerging consensus that slow‐cycling SOM generally consists of relatively low molecular weight organic carbon substrates that enter the mineral soil as dissolved organic matter and associate with mineral surfaces (referred to as “mineral‐associated OM,” or MAOM). However, much debate and contradictory evidence persist around: (a) whether the organic C substrates within the MAOM pool primarily originate from aboveground vs. belowground plant sources and (b) whether C substrates directly sorb to mineral surfaces or undergo microbial transformation prior to their incorporation into MAOM. Here, we attempt to reconcile disparate views on the formation of MAOM by proposing a spatially explicit set of processes that link plant C source with MAOM formation pathway. Specifically, because belowground vs. aboveground sources of plant C enter spatially distinct regions of the mineral soil, we propose that fine‐scale differences in microbial abundance should determine the probability of substrate–microbe vs. substrate–mineral interaction. Thus, formation of MAOM in areas of high microbial density (e.g., the rhizosphere and other microbial hotspots) should primarily occur through an in vivo microbial turnover pathway and favor C substrates that are first biosynthesized with high microbial carbon‐use efficiency prior to incorporation in the MAOM pool. In contrast, in areas of low microbial density (e.g., certain regions of the bulk soil), MAOM formation should primarily occur through the direct sorption of intact or partially oxidized plant compounds to uncolonized mineral surfaces, minimizing the importance of carbon‐use efficiency, and favoring C substrates with strong “sorptive affinity.” Through this framework, we thus describe how the primacy of biotic vs. abiotic controls on MAOM dynamics is not mutually exclusive, but rather spatially dictated. Such an understanding may be integral to more accurately modeling soil organic matter dynamics across different spatial scales.
Subfields: Ecology, Environmental Chemistry, Soil Science
View Paper: https://www.semanticscholar.org/paper/d487e76b857bfda516d0ebff30b1ae614d16be41
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In Ecology
- I. Kögel‐Knabner
- K. Smalla
- P. Nannipieri
- M. Roberfroid
- Danilo Ercolini
- L. Gianfreda
- M. Rao
- D. Griffin
In Soil Science
Citations in the corpus
- Rhizosphere Spatiotemporal Organization–A Key to Rhizosphere Functions (2018, background): “It is to be expected that rhizodeposition has a strong effect, not only on microbial C processing, but also on the stabilization of organic C in soils and hence carbon storage (Frey, 2019; Sokol et al., 2019).”
- Conceptualizing soil organic matter into particulate and mineral‐associated forms to address global change in the 21st century (2019, background): “…sequestered long term and its vulnerability to global change factors minimized, such as at depth (Chenu et al., 2019; Hicks Pries et al., 2018) where its decomposition could be inhibited by lack of fresh C supply (Fontaine et al., 2007) or spatial separation from decomposers (Sokol et al., 2018).”