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Abstract Conceptual and empirical advances in soil biogeochemistry have challenged long-held assumptions about the role of soil micro-organisms in soil organic carbon (SOC) dynamics; yet, rigorous tests of emerging concepts remain sparse. Recent hypotheses suggest that microbial necromass production links plant inputs to SOC accumulation, with high-quality (i.e., rapidly decomposing) plant litter promoting microbial carbon use efficiency, growth, and turnover leading to more mineral stabilization of necromass. We test this hypothesis experimentally and with observations across six eastern US forests, using stable isotopes to measure microbial traits and SOC dynamics. Here we show, in both studies, that microbial growth, efficiency, and turnover are negatively (not positively) related to mineral-associated SOC. In the experiment, stimulation of microbial growth by high-quality litter enhances SOC decomposition, offsetting the positive effect of litter quality on SOC stabilization. We suggest that microbial necromass production is not the primary driver of SOC persistence in temperate forests. Factors such as microbial necromass origin, alternative SOC formation pathways, priming effects, and soil abiotic properties can strongly decouple microbial growth, efficiency, and turnover from mineral-associated SOC.
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Rethinking assumptions about plant litter decomposition
Abstract Plant litter decomposition is the breakdown of dead plant biomass by abiotic and biotic means. In terrestrial ecosystems, decomposition regulates the fate of fixed plant carbon, contributing both to its release into the atmosphere and its long-term storage in soil organic matter. In the present article, we revisit four assumptions about decomposition in light of advances in microbiology. First, we consider fungi as primary decomposers, noting bacterial contributions to breaking down lignin and cellulose and overcoming nitrogen limitation. Second, we discuss evidence of the role of microbial communities on litter decomposition, challenging assumptions of microbial redundancy. Third, given these functional consequences of their composition, we examine whether surface litter and bulk soil microbial communities are interchangeable. Finally, we reevaluate the idea that soil organic matter originates from plant litter, emphasizing the pivotal role of microbial necromass. We highlight the importance of integrating microbiological findings into ecosystem ecology to accelerate research on carbon cycling in terrestrial ecosystems.
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- Award ID(s):
- 2113004
- PAR ID:
- 10586277
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- BioScience
- ISSN:
- 0006-3568
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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