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Carbon mineralization and microbial activity in agricultural topsoil and subsoil as regulated by root nitrogen and recalcitrant carbon concentrations

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Liang, Zhi; Elsgaard, Lars; Nicolaisen, Mette; Lyhne-Kjæbye, Annemette and Olesen, Jørgen E. (2018) Carbon mineralization and microbial activity in agricultural topsoil and subsoil as regulated by root nitrogen and recalcitrant carbon concentrations. Plant and Soil, None, pp. 1-18.

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Summary

Aims Mechanisms of subsoil carbon sequestration from deep-rooted plants are elusive, but may contribute to climate change mitigation. This study addressed the role of root chemistry on carbon mineralization and microbiology in a temperate agricultural subsoil (60 and 300 cm depth)compared to topsoil (20 cm depth).
Methods Roots from different plant species were chemically characterized and root-induced CO2 production was measured in controlled soil incubations (20 weeks). Total carbon losses, β-glucosidase activity, carbon substrate utilization, and bacterial gene copy numbers were determined. After 20 weeks, resultant carbon mineralization responses to mineral nitrogen (N) were tested.
Results Root-induced carbon losses were significantly lower in subsoils (32–41%) than in topsoil (58%). Carbon losses varied according to root chemistry and were mainly linked to root N concentration for subsoils and to lignin and hemicellulose concentration for topsoil. Increases in β-glucosidase activity and bacterial numbers in subsoils were also linked to rootN concentration. Added mineral N preferentially stimulated CO2 production from roots with low concentrations of N, lignin and hemicellulose.
Conclusions The results were compatible with a concept of N availability and chemically recalcitrant root compounds interacting to control subsoil carbon decomposition. Implications for carbon sequestration from deep-rooted plants are discussed.


EPrint Type:Journal paper
Keywords:Root chemistry. Nitrogen . Lignin . Carbon mineralization . Subsoil
Subjects: Soil > Soil quality > Soil biology
Research affiliation: Denmark > Private funders/foundations > Deep Frontier
ISSN:Print: 0032-079X, Online: 1573-5036
DOI:10.1007/s11104-018-3826-z
Deposited By: Liang, Zhi
ID Code:33966
Deposited On:15 Nov 2018 12:34
Last Modified:15 Nov 2018 12:34
Document Language:English
Status:Published
Refereed:Peer-reviewed and accepted

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