Exogenous iron mitigates photo-facilitation of soil organic matter

IF 4.5 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Geochimica et Cosmochimica Acta Pub Date : 2025-03-13 DOI:10.1016/j.gca.2025.03.010

Yongli Wen , Jiali Wu , Xueting Wen , Zhuoyue Zhang , Jian Wang , Guanghui Yu , Xinhua He , Maohong Xu , Man Cheng , Wenjuan Liu , Jian Xiao

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引用次数: 0

Abstract

Subalpine meadow soil carbon (C) is susceptible to ultraviolet B (UV-B) radiation, yet the mechanisms of UVB-induced soil organic C (SOC) photodegradation and the influence of iron (Fe) on this susceptibility remain largely unknown. In this study, soils from the southeastern (SE) and northwestern (NW) slopes of a subalpine meadow were exposed to three UVB treatments, elevated (ele-UVB, ∼120 μW·cm⁻²), ambient (amb-UVB, ∼60 μW·cm⁻²), or attenuated (no-UVB, 0 μW·cm⁻²), to assess the effects of UV radiation and Fe addition on SOC mineralization. A two-phase lignin incubation experiment was then conducted to elucidate the mechanism by which Fe influences the abiotic and biotic processes of lignin photodegradation. Results showed that ele-UVB increased SOC degradation by 137 % and 34 % in the SE and NW soils, respectively. Lignin phenols underwent significant photochemical degradation, which was mitigated by Fe addition. Furthermore, our findings revealed that photo-facilitation (i.e., microbial decomposition) significantly contributed to lignin photodegradation, releasing over 5 times more CO₂ than abiotic degradation did. This occurred mainly due to the depolymerization of lignin macromolecules, which increased the substrate availability for microbes, rather than shifts in microbial community composition. Fe impacted photo-facilitation by binding with lignin derivatives, reducing microbial accessibility and limiting their decomposition. These findings highlight the intricate interactions among UV-B radiation, Fe, and microbial processes in SOC turnover, offering critical insights for soil C management under global environmental change scenarios.

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外源铁减缓了土壤有机质的光促进作用

亚高寒草甸土壤碳(C)对紫外线B （UV-B）辐射敏感，但uvb诱导土壤有机碳（SOC）光降解的机制以及铁（Fe）对这种敏感性的影响在很大程度上尚不清楚。本研究以亚高寒草甸东南（SE）和西北（NW）斜坡的土壤为研究对象，采用高强度UVB处理（高强度UVB， ~ 120 μW·cm−2）、低强度UVB处理（低强度UVB， ~ 60 μW·cm−2）和弱强度UVB处理（低强度UVB， ~ 0 μW·cm−2），评价了UV辐射和Fe添加对有机碳矿化的影响。然后进行了两相木质素培养实验，以阐明铁对木质素光降解的非生物和生物过程的影响机制。结果表明，ele-UVB对东南和西北土壤有机碳的降解作用分别提高了137%和34%。木质素酚类物质发生了明显的光化学降解，铁的加入减轻了这一降解。此外，我们的研究结果表明，光促进（即微生物分解）显著促进木质素的光降解，释放的二氧化碳比非生物降解多5倍以上。这主要是由于木质素大分子的解聚，增加了微生物的底物可用性，而不是微生物群落组成的变化。铁通过与木质素衍生物结合，降低微生物的可及性并限制其分解，从而影响光促进作用。这些发现强调了UV-B辐射、Fe和微生物过程在有机碳周转中的复杂相互作用，为全球环境变化情景下的土壤C管理提供了重要见解。

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来源期刊

Geochimica et Cosmochimica Acta 地学-地球化学与地球物理

CiteScore

9.60

自引率

14.00%

发文量

437

审稿时长

6 months

期刊介绍： Geochimica et Cosmochimica Acta publishes research papers in a wide range of subjects in terrestrial geochemistry, meteoritics, and planetary geochemistry. The scope of the journal includes: 1). Physical chemistry of gases, aqueous solutions, glasses, and crystalline solids 2). Igneous and metamorphic petrology 3). Chemical processes in the atmosphere, hydrosphere, biosphere, and lithosphere of the Earth 4). Organic geochemistry 5). Isotope geochemistry 6). Meteoritics and meteorite impacts 7). Lunar science; and 8). Planetary geochemistry.