Pedosphere (4): 962--971, 2026
ISSN 1002-0160/CN 32-1315/P
©2026 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Effects of low-molecular-weight organic substances, biochars and temperature on microbial carbon use efficiency |
Simon KOHLMANN1, Isabel GREENBERG1, Rainer Georg JOERGENSEN2, Michaela A. DIPPOLD3, Bernard LUDWIG1 |
1 Department of Environmental Chemistry, University of Kassel, Nordbahnhofstraße 1a, Witzenhausen 37213 (Germany);
2 Department of Soil Biology and Plant Nutrition, University of Kassel, Nordbahnhofstraße 1a, Witzenhausen 37213 (Germany);
3 Geo-Biosphere Interactions, Department of Geosciences, University of Tübingen, Schnarrenbergstraße 94-96, Tübingen 72076 (Germany) |
| ABSTRACT |
| Microbial carbon (C) use efficiency (CUE) is a key parameter affecting soil C decomposition while being affected by substrate, soil amendment, and temperature. Moreover, different CUE calculation approaches exist, and quantitative comparisons are scarce. Our objectives were to investigate the short-term effects of 13C-labeled low-molecular-weight organic substances (alanine and glucose), incubation temperatures (15 and 25 ℃), and biochars (produced from corn cob, miscanthus, and grass silage) on CUE. Soil samples were taken from an arable loess site and incubated with or without artificially aged biochar and 13C-labeled alanine or glucose at 60% water-holding capacity at 15 or 25 ℃ for 5 d. The cumulative total carbon dioxide (CO2)-C (CO2-CT) and substrate-derived CO2-C (CO2-CSD) emissions were determined. In addition, microbial biomass C (MBC), including total MBC (MBCT) and substrate-derived MBC (MBCSD), was determined. The CUE accounting for total microbial products including all freshly synthesized microbial non-biomass metabolites that leave the cells (CUETP) and the CUE solely considering the incorporation of substrate-derived C into MBC (CUEMB, determined as the ratio of MBC growth to subtrate C uptake) were calculated. Analysis of variance showed that cumulative CO2-CT emission was significantly (P ≤ 0.05) affected by incubation temperature, substrate, and biochar, whereas cumulative CO2-CSD emission was significantly stimulated only by substrate and temperature. The CUETP showed a significant response to substrate type and was reduced at the higher incubation temperature. The CUETP, MBCT, and MBCSD values at both incubation temperatures confirmed the greater importance of glucose for MBC formation compared to alanine, while alanine was mineralized to a greater extent. The decrease in CUETP at the higher temperature for both substrates indicated the increasing importance of the substrates for energy production. The artificially aged biochars in this study significantly stimulated cumulative CO2-CT emission but not CUETP, cumulative CO2-CSD emission, MBCT content, or MBCSD content. The CUEMB values were significantly lower than the CUETP values and were affected differently by the factors studied. Overall, CUETP should preferably be reported over CUEMB because the exogenous metabolism of soil microorganisms should be taken into account when calculating CUE values. |
| Key Words: alanine,artificially aged biochar,carbon emission,endogenous metabolism,exogenous metabolism,glucose,isotope,microbial biomass,microbial necromass carbon |
| Citation: Kohlmann S, Greenberg I, Joergensen R G, Dippold M A, Ludwig B. 2026. Effects of low-molecular-weight organic substances, biochars and temperature on microbial carbon use efficiency. Pedosphere. 36(4): 962-971. |
|
View Full Text
|
|
|
|
