TY - JOUR

T1 - Biogeochemical limitations of carbon stabilization in forest subsoils

AU - Liebmann, Patrick

AU - Mikutta, Robert

AU - Kalbitz, Karsten

AU - Wordell-Dietrich, Patrick

AU - Leinemann, Timo

AU - Preusser, Sebastian

AU - Mewes, Ole

AU - Perrin, Eike

AU - Bachmann, Jörg

AU - Don, Axel

AU - Kandeler, Ellen

AU - Marschner, Bernd

AU - Schaarschmidt, Frank

AU - Guggenberger, Georg

N1 - Funding Information: We thank Martin Volkmann, Hanna B?hme, Susanne K. Woche, and Frank Hegewald for their help in the field, and Heike Steffen and Anne Kathrin Herwig for sample preparations. We thank Manuela Unger for the DO13C measurements and Heike Haslwimmer for molecular analyses (qPCR data). Carsten Beyer is acknowledged for the analysis of the DOM composition. Financial support for this work was provided by the Deutsche Forschungsgemeinschaft (DFG) within the framework of the DFG Research Unit 1806 ?The forgotten Part of Carbon Cycling: Organic Matter Storage and Turnover in Subsoils (SUBSOM)? and the individual grants GU 406/28?1,2, KA 1737/15?2, MI 1377/10?2, DO 1734/4?2, KA 1590/11?2, BA1359/13?2, BA1359/14?2, and MA 1830/14?2. Open access funding enabled and organized by Projekt DEAL.

PY - 2022/2/8

Y1 - 2022/2/8

N2 - Background: Soils are important carbon (C) sinks or sources and thus of utmost importance for global carbon cycling. Particularly, subsoils are considered to have a high potential for additional C storage due to mineral surfaces still available for sorptive stabilization. Aims: Little information exists about the extent to which additional litter-derived C is transferred to and stabilized in subsoils. This study aimed at evaluating the role of litter-derived dissolved organic matter (DOM) inputs for the formation of stable mineral-associated C in subsoils. Methods: We carried out a multiple-method approach including field labeling with 13C-enriched litter, exposure of 13C-loaded reactive minerals to top- and subsoils, and laboratory sorption experiments. Results: For temperate forest soils, we found that the laboratory-based C sink capacity of subsoils is unlikely to be reached under field conditions. Surface C inputs via litter leachates are little conducive to the subsoil C pool. Only 0.5% of litter-derived C entered the subsoil as DOM within nearly 2 years and most of the recently sorbed C is prone to fast microbial mineralization rather than long-term mineral retention. Desorption to the soil solution and an adapted microbial community re-mobilize organic matter in subsoils faster than considered so far. Conclusions: We conclude that the factors controlling the current mineral retention and stabilization of C within temperate forest subsoils will likewise limit additional C uptake. Thus, in contrast to their widely debated potential to accrue more C, the role of forest subsoils as future C sink is likely overestimated and needs further reconsideration.

AB - Background: Soils are important carbon (C) sinks or sources and thus of utmost importance for global carbon cycling. Particularly, subsoils are considered to have a high potential for additional C storage due to mineral surfaces still available for sorptive stabilization. Aims: Little information exists about the extent to which additional litter-derived C is transferred to and stabilized in subsoils. This study aimed at evaluating the role of litter-derived dissolved organic matter (DOM) inputs for the formation of stable mineral-associated C in subsoils. Methods: We carried out a multiple-method approach including field labeling with 13C-enriched litter, exposure of 13C-loaded reactive minerals to top- and subsoils, and laboratory sorption experiments. Results: For temperate forest soils, we found that the laboratory-based C sink capacity of subsoils is unlikely to be reached under field conditions. Surface C inputs via litter leachates are little conducive to the subsoil C pool. Only 0.5% of litter-derived C entered the subsoil as DOM within nearly 2 years and most of the recently sorbed C is prone to fast microbial mineralization rather than long-term mineral retention. Desorption to the soil solution and an adapted microbial community re-mobilize organic matter in subsoils faster than considered so far. Conclusions: We conclude that the factors controlling the current mineral retention and stabilization of C within temperate forest subsoils will likewise limit additional C uptake. Thus, in contrast to their widely debated potential to accrue more C, the role of forest subsoils as future C sink is likely overestimated and needs further reconsideration.

KW - carbon cycling

KW - climate change mitigation

KW - microbial community composition

KW - mineral-associated organic carbon

UR - http://www.scopus.com/inward/record.url?scp=85117920978&partnerID=8YFLogxK

U2 - 10.1002/jpln.202100295

DO - 10.1002/jpln.202100295

M3 - Article

AN - SCOPUS:85117920978

VL - 185

SP - 35

EP - 43

JO - Journal of Plant Nutrition and Soil Science

JF - Journal of Plant Nutrition and Soil Science

SN - 1436-8730

IS - 1

ER -