Microbial and abiotic controls on mineral-associated organic matter in soil profiles along an ecosystem gradient

authored by

Robert Mikutta, Stephanie Turner, Axel Schippers, Norman Gentsch, Sandra Meyer-Stüve, Leo M. Condron, Duane A. Peltzer, Sarah J. Richardson, Andre Eger, Günter Hempel, Klaus Kaiser, Thimo Klotzbücher, Georg Guggenberger

Abstract

Formation of mineral-organic associations is a key process in the global carbon cycle. Recent concepts propose litter quality-controlled microbial assimilation and direct sorption processes as main factors in transferring carbon from plant litter into mineral-organic associations. We explored the pathways of the formation of mineral-associated organic matter (MOM) in soil profiles along a 120-ky ecosystem gradient that developed under humid climate from the retreating Franz Josef Glacier in New Zealand. We determined the stocks of particulate and mineral-associated carbon, the isotope signature and microbial decomposability of organic matter, and plant and microbial biomarkers (lignin phenols, amino sugars and acids) in MOM. Results revealed that litter quality had little effect on the accumulation of mineral-associated carbon and that plant-derived carbon bypassed microbial assimilation at all soil depths. Seemingly, MOM forms by sorption of microbial as well as plant-derived compounds to minerals. The MOM in carbon-saturated topsoil was characterized by the steady exchange of older for recent carbon, while subsoil MOM arises from retention of organic matter transported with percolating water. Overall, MOM formation is not monocausal but involves various mechanisms and processes, with reactive minerals being effective filters capable of erasing chemical differences in organic matter inputs.

Organisation(s)

Institute of Soil Science
Leibniz Research Centre FZ:GEO

External Organisation(s)

Martin Luther University Halle-Wittenberg
Federal Institute for Geosciences and Natural Resources (BGR)
Lincoln University
Landcare Research

Type

Article

Journal

Scientific reports

Volume

9

ISSN

2045-2322

Publication date

16.07.2019

Publication status

E-pub ahead of print

Peer reviewed

Yes

ASJC Scopus subject areas

General

Sustainable Development Goals

SDG 13 - Climate Action

Electronic version(s)

https://doi.org/10.1038/s41598-019-46501-4 (Access: Open)
https://doi.org/10.15488/8622 (Access: Open)