TY - JOUR

T1 - Stable isotopes reveal that fungal residues contribute more to mineral-associated organic matter pools than plant residues

AU - Klink, Saskia

AU - Keller, Adrienne B.

AU - Wild, Andreas J.

AU - Baumert, Vera L.

AU - Gube, Matthias

AU - Lehndorff, Eva

AU - Meyer, Nele

AU - Mueller, Carsten W.

AU - Phillips, Richard P.

AU - Pausch, Johanna

N1 - Funding Information: We want to thank IU RTP and preserve manager Michael Chitwood. Special thanks to Elizabeth Huenupi-Pena for assistance with organizing field and lab equipment and shipping and to Ilse Thaufelder for helping with sampling and sample preparation. We thank Steven Russell and Ronald Kerner for their help with fungal sporocarp identification. Thanks to Sofia Gomes for DNA analyses of fungi in tree roots. Many thanks to the BayCEER Laboratory of Isotope Biogeochemistry (University of Bayreuth, Germany) and the Centre for Stable Isotope Research and Analysis (Georg-August-University Göttingen, Germany) for stable isotope analyses. This work was funded by the German Research Foundation (DFG) under project PA 2377/2-1/GU 1309/5-1 “Towards a predictive understanding on how mycorrhizal types influence the decomposition of soil organic matter”. Part of the lab work and chemical analyzes were funded by the DFG project “Rhizosphere as driver of subsoil organic matter distribution and composition” ( MU3021/4-2 ) in the frame of the research unit “The Forgotten Part of Carbon Cycling: Soil Organic Matter Storage and Turnover in Subsoils (SUBSOM)” (FOR1806). Publisher Copyright: © 2022 Elsevier Ltd

PY - 2022

Y1 - 2022

N2 - We still lack crucial knowledge about the contribution of plant vs. microbial residues to specific SOM pools, particularly the relative contribution of arbuscular (AM), ectomycorrhizal (ECM), and saprotrophic (SAP) fungi. We investigated sources of particulate and mineral-associated organic matter (POM and MAOM) around trees with distinct mycorrhizal types, Liriodendron tulipifera (AM-association) and Quercus alba (ECM-association), in a temperate deciduous forest in Indiana, USA. Combining 13C and 15N natural abundance analyses with measurements of microbial residues using amino sugars, the isotope signatures of large, medium and small-sized POM and MAOM fractions were compared with those of leaves, roots and biomass of mycorrhizal and saprotrophic fungi. A Bayesian inference isotope mixing model calculated sources of C and N to SOM fractions. While the isotope composition of POM resembled that of plants, MAOM was close to fungal values. This was confirmed by mixing model calculations and microbial residue analysis, which additionally and independent from tree partner suggested saprobic fungi contributing with 4–53% to POM and 23–42% to MAOM, as opposed to ECM contributions. Our results suggest fungal, not plant residues, as the source of the most putatively stable OM pool; thus, altering fungal communities may enhance efforts to increase long-term soil C storage.

AB - We still lack crucial knowledge about the contribution of plant vs. microbial residues to specific SOM pools, particularly the relative contribution of arbuscular (AM), ectomycorrhizal (ECM), and saprotrophic (SAP) fungi. We investigated sources of particulate and mineral-associated organic matter (POM and MAOM) around trees with distinct mycorrhizal types, Liriodendron tulipifera (AM-association) and Quercus alba (ECM-association), in a temperate deciduous forest in Indiana, USA. Combining 13C and 15N natural abundance analyses with measurements of microbial residues using amino sugars, the isotope signatures of large, medium and small-sized POM and MAOM fractions were compared with those of leaves, roots and biomass of mycorrhizal and saprotrophic fungi. A Bayesian inference isotope mixing model calculated sources of C and N to SOM fractions. While the isotope composition of POM resembled that of plants, MAOM was close to fungal values. This was confirmed by mixing model calculations and microbial residue analysis, which additionally and independent from tree partner suggested saprobic fungi contributing with 4–53% to POM and 23–42% to MAOM, as opposed to ECM contributions. Our results suggest fungal, not plant residues, as the source of the most putatively stable OM pool; thus, altering fungal communities may enhance efforts to increase long-term soil C storage.

KW - Amino sugars

KW - MEMS hypothesis

KW - Mineral-associated organic matter

KW - Particulate organic matter

KW - Soil organic matter dynamics

KW - Stable isotopes

U2 - 10.1016/j.soilbio.2022.108634

DO - 10.1016/j.soilbio.2022.108634

M3 - Journal article

AN - SCOPUS:85127350645

VL - 168

JO - Soil Biology & Biochemistry

JF - Soil Biology & Biochemistry

SN - 0038-0717

M1 - 108634

ER -