Biogeochemical limitations of carbon stabilization in forest subsoils

authored by

Patrick Liebmann, Robert Mikutta, Karsten Kalbitz, Patrick Wordell-Dietrich, Timo Leinemann, Sebastian Preusser, Ole Mewes, Eike Perrin, Jörg Bachmann, Axel Don, Ellen Kandeler, Bernd Marschner, Frank Schaarschmidt, Georg Guggenberger

Abstract

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.

Organisation(s)

Institute of Soil Science
Department of Biostatistics

External Organisation(s)

Martin Luther University Halle-Wittenberg
Technische Universität Dresden
Johann Heinrich von Thünen Institute, Federal Research Institute for Rural Areas, Forestry and Fisheries
University of Hohenheim
Ruhr-Universität Bochum

Type

Article

Journal

Journal of Plant Nutrition and Soil Science

Volume

185

Pages

35-43

No. of pages

9

ISSN

1436-8730

Publication date

08.02.2022

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Soil Science, Plant Science

Sustainable Development Goals

SDG 13 - Climate Action

Electronic version(s)

https://doi.org/10.1002/jpln.202100295 (Access: Open)