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Decreased rhizodeposition, but increased microbial carbon stabilization with soil depth down to 3.6 m

Peixoto, Leanne; Elsgaard, Lars; Rasmussen, Jim; Kuzyakov, Yakov; Banfield, Callum C.; Dippold, Michaela A. and Olesen, Jørgen E. (2020) Decreased rhizodeposition, but increased microbial carbon stabilization with soil depth down to 3.6 m. Soil Biology and Biochemistry, 150, p. 108008.

[thumbnail of Peixoto et al 2020 SBB.pdf] PDF - Published Version - English


Despite the importance of subsoil carbon (C) deposition by deep-rooted crops in mitigating climate change and maintaining soil health, the quantification of root C input and its microbial utilization and stabilization below 1 m depth remains unexplored. We studied C input by three perennial deep-rooted plants (lucerne, kernza, and rosinweed) grown in a unique 4-m deep RootTower facility. 13C multiple pulse labeling was applied to trace C flows in roots, rhizodeposition, and soil as well as 13C incorporation into microbial groups by phospholipid fatty acids and the long-term stabilization of microbial residues by amino sugars. The ratio of rhizodeposited 13C in the PLFA and amino sugar pools was used to compare the relative microbial stability of rhizodeposited C across depths and plant species. Belowground C allocation between roots, rhizodeposits, and living and dead microorganisms indicated depth dependent plant investment. Rhizodeposition as a fraction of the total belowground C input declined from the topsoil (0–25 cm) to the deepest layer (360 cm), i.e., from 35%, 45%, and 36%–8.0%, 2.5%, and 2.7% for lucerne, kernza, and rosinweed, respectively, where lucerne had greater C input than the other species between 340 and 360 cm. The relative microbial stabilization of rhizodeposits in the subsoil across all species showed a dominance of recently assimilated C in microbial necromass, thus indicating a higher microbial stabilization of rhizodeposited C with depth. In conclusion, we traced photosynthates down to 3.6 m soil depth and showed that even relatively small C amounts allocated to deep soil layers will become microbially stabilized. Thus, deep-rooted crops, in particular lucerne are important for stabilization and storage of C over long time scales in deep soil.

EPrint Type:Journal paper
Agrovoc keywords:
Subjects: Soil > Soil quality > Soil biology
Soil > Nutrient turnover
Research affiliation: Denmark > AU - Aarhus University
Denmark > Private funders/foundations > Deep Frontier
Deposited By: Peixoto, Mrs Leanne
ID Code:38469
Deposited On:06 Oct 2020 14:09
Last Modified:06 Oct 2020 14:09
Document Language:English
Refereed:Peer-reviewed and accepted

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