Wetland soil organic carbon balance is reversed by old carbon and iron oxide additions

Bingbo Ni; Xiaofei Yu; Xun Duan; Yuanchun Zou

doi:10.3389/fmicb.2023.1327265

Wetland soil organic carbon balance is reversed by old carbon and iron oxide additions

Front Microbiol. 2024 Jan 8:14:1327265. doi: 10.3389/fmicb.2023.1327265. eCollection 2023.

Authors

Bingbo Ni^{1

2}, Xiaofei Yu³, Xun Duan^{1

2}, Yuanchun Zou¹

Affiliations

¹ State Key Laboratory of Black Soils Conservation and Utilization and Heilongjiang Xingkai Lake Wetland Ecosystem National Observation and Research Station and Key Laboratory of Wetland Ecology and Environment and Jilin Provincial Joint Key Laboratory of Changbai Mountain Wetland and Ecology, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun, China.
² University of Chinese Academy of Sciences, Beijing, China.
³ State Environmental Protection Key Laboratory for Wetland Conservation and Vegetation Restoration and Jilin Provincial Key Laboratory of Ecological Restoration and Ecosystem Management and Key Laboratory of Vegetation Ecology of Ministry of Education, School of Environment, Northeast Normal University, Changchun, China.

Abstract

Iron (Fe) oxides can stabilize organic carbon (OC) through adsorption and co-precipitation, while microbial Fe reduction can disrupt Fe-bound OC (Fe-OC) and further increase OC mineralization. The net effects of OC preservation and mineralization mediated by Fe oxides are still unclear, especially for old carbon (formed from plant litters over millions of years) and crystalline Fe oxides. Accelerating the recovery of wetland carbon sinks is critical for mitigating climate change and achieving carbon neutrality. Quantifying the net effect of Fe-mediated OC mineralization and preservation is vital for understanding the role of crystalline Fe oxides in carbon cycling and promoting the recovery of soil carbon sinks. Here, we explored the OC balances mediated by hematite (Hem) and lignite addition (Lig) to freshwater wetland (FW, rich in C and Fe) and saline-alkaline wetland (SW, poor in C and Fe) soil slurries, incubated under anaerobic conditions. Results showed that Lig caused net OC accumulation (FW: 5.9 ± 3.6 mg g^-1; SW: 8.3 ± 3.2 mg g^-1), while Hem caused dramatic OC loss, particularly in the FW soils. Hem inhibited microbial Fe(III) reduction by decreasing the relative abundance of Fe respiration reducers, while substantially enhancing OC mineralization through the shift in the microbial community structure of FW soils. Lig resulted in carbon emission, but its contribution to preservation by the formation of Fe-OC was far higher than that which caused OC loss. We concluded that crystalline Fe oxide addition solely favored the increase of OC mineralization by adjusting the microbial community structure, while old carbon enriched with an aromatic and alkyl promoted Fe-OC formation and further increased OC persistence. Our findings could be employed for wetland restoration, particularly for the recovery of soil carbon sinks.

Keywords: Iron-bound organic carbon; freshwater mire; organic carbon dynamics; saline-alkaline marsh; trade-off effects.

Grants and funding

The author(s) declare that financial support was received for the research, authorship, and/or publication of this article. This study was supported by the National Natural Science Foundation of China (41971136, 42222102, 42230516, and 42171107), and the Department of Science and Technology of Jilin Province (20230508089RC).