Long-Term Warming Decreases Redox Capacity of Soil Organic Matter

Abstract

Globally rising temperatures increase microbial activity, accelerating decomposition of soil organic matter (SOM). SOM has numerous functional capabilities, of which the capacity to engage in reduction–oxidation reactions (or redox capacity) affects nearly all soil biogeochemical processes. How warming-induced microbial decomposition affects the redox capacity of SOM and its functional role in biogeochemical processes is largely unknown. We examined the impact of 15 years of in situ soil warming on the redox capacities of water-extractable organic matter (WEOM). Combining mediated electrochemical analysis with high-resolution mass spectrometry, we assessed the molecular basis for changes in the redox capacities of WEOM within heated (5°C above ambient) and non-heated organic and mineral temperate forest soils. Chronic soil warming significantly decreased both concentrations and inherent electron-accepting and -donating capacities of WEOM, particularly in the mineral soil. This decline was best explained by decreases in the relative abundance of aromatic and phenolic compounds, suggesting that enhanced microbial decomposition of redox-active moieties caused the decrease in redox capacity. Our findings suggest that global warming not only diminishes the size of the soil carbon reservoir but might also negatively alter the ability of SOM to participate in critical redox processes such as microbial respiration, nutrient cycling, or contaminant degradation.

Coupled Sorption and Oxidation of Soil Dissolved Organic Matter on Manganese Oxides: Nano/Sub-nanoscale Distribution and Molecular Transformation

“…Based on the O/C ratio and H/C ratio, all compounds detected were classified into several major biochemical classes (Table S3, SI). , Duplicates of the original DOM sample showed a good reproducibility of the FT-ICR-MS analysis (Figure S2, SI). We further conducted Pearson’s correlation analysis on the relative intensities of all molecules found in duplicate samples of the original DOM, which also showed a high reproducibility ( r = 0.951, p < 0.001).…”

Redox-induced transformation of potentially toxic elements with organic carbon in soil

“…1-3 and Fig. 2) (Bai et al 2020;LaCroix et al 2021). For instance, the quinone can accept electrons with the formation of hydroquinone, thus causing oxidation (Eq.…”

“…Second, the addition of carbon into the soil has been widely conducted as a potential method for fertility enhancement, environmental remediation, and carbon sequestration, leading to the increased organic carbon content in the soil. Notably, this newly added carbon could have different properties compared to the indigenous organic carbon owing to its formation process and aging impact (LaCroix et al 2021;Wang et al 2020c). Thus, it is vital to consider the unintended consequence and potential risk of adding carbon to the soil in future studies, including both the direct mobilization of PTEs and the indirect transformation with the soil moieties.…”

“…The impact of different organic carbon on fertility, soil remediation, and carbon sequestration is systematically studied (Hoffland et al 2020;Lehmann and Kleber 2015;Maestrini et al 2015;Ondrasek et al 2019; Smreczak and Ukalska-Jaruga 2021; Verbeeck et al 2020;Woolet and Whitman 2020), and their potential role in the abiotic redox-induced transformation of pollutants in soil has been highlighted recently (Aftabtalab et al 2022;LaCroix et al 2021;Xu et al 2020cXu et al , 2022b. The considerable redox capacity of organic carbon could directly affect the redox reaction of potentially toxic elements (PTEs), which are the trace elements with the potential toxicity to humans.…”

Warming drives sustained plant phosphorus demand in a humid tropical forest

“…A large proportion of P bound to iron (Fe) oxides (Borch & Fendorf, 2007) could be released following Fe reduction due to redox fluctuations in humid tropical soils (Chacón et al, 2006; Gross et al, 2020; Peretyazhko & Sposito, 2005). It has been recently found that warming may change microbial metabolism and thus soil redox conditions (LaCroix et al, 2021), which could potentially affect the conversion of Fe‐bound P. However, no published study has assessed these P conversion processes under warming to determine plant P demand status, although P resorption is a crucial strategy for plants and redox fluctuations often occur in P‐deficient and humid forests.…”