State Key Laboratory of Estuarine and Coastal Research, Institute of Eco-Chongming, East China Normal University, Shanghai, China; Yangtze Delta Estuarine Wetland Ecosystem Observation and Research Station, Ministry of Education, Shanghai Science and Technology Committee, China.
State Key Laboratory of Estuarine and Coastal Research, Institute of Eco-Chongming, East China Normal University, Shanghai, China; Yangtze Delta Estuarine Wetland Ecosystem Observation and Research Station, Ministry of Education, Shanghai Science and Technology Committee, China.
Sci Total Environ. 2024 Dec 10;955:177214. doi: 10.1016/j.scitotenv.2024.177214. Epub 2024 Nov 1.
Iron (Fe) oxides in wetland soils are crucial for stabilizing soil organic carbon (SOC) by forming stable Fe-OC complexes, thus protecting SOC from microbial breakdown and aiding its preservation. This study delves into the response of Fe (hydr-)oxides to salt stress, a relatively unexplored area, by examining Kandelia obovata, a key mangrove species. Through controlled climate chamber experiments, we investigated how salt stress affects the interactions between Fe (hydr-)oxides and SOC in root exudates (REs) and rhizosphere soils. Our results demonstrate that salinity at 30 ppt significantly increases the release of sugars, amino acids, inorganic nutrients (NH, NO), and phosphorus in K. obovata's REs, while reducing crystalline and amorphous Fe (hydr-)oxides and increasing complexed Fe (hydr-)oxide levels, thereby reducing their crystallinity in rhizosphere soils. Importantly, at elevated salinity (30 ppt), the Fe-OC bond in the rhizosphere shows greater stability, indicating enhanced resilience to salt stress compared to bulk soil. Salt stress also raises the carbon to nitrogen (C/N) ratio in REs. Testing artificial REs (AREs) with different C/N ratios showed that Fe (hydr-)oxide content decreases at C/N ratios of 10 and 30 compared to the control, whereas Fe-OC content increases with higher C/N ratios. Introduction of AREs with a C/N ratio of 20 significantly affected rhizosphere crystalline Fe (hydr-)oxide and Fe-OC content, highlighting AREs' impact on the binding of Fe (hydr-) oxides and OC. The presence of soil microorganisms was critical for the binding of Fe (hydr-) oxides and OC, as sterilized soil exhibited significantly lower levels of Fe (hydr-) oxides and Fe-OC compared to unsterilized soil. This research reveals that under salt stress, mangrove plants play a crucial role in stabilizing rhizosphere SOC by influencing Fe (hydr-) oxide crystallinity and promoting the formation of stable Fe-OC complexes, highlighting the complex interactions between plant REs, salt stress, and soil minerals.
湿地土壤中的铁（Fe）氧化物对于通过形成稳定的 Fe-OC 配合物来稳定土壤有机碳（SOC）至关重要，从而保护 SOC 免受微生物分解并有助于其保存。本研究通过检查红树林关键物种秋茄（Kandelia obovata），深入研究了 Fe（水合）氧化物对盐分胁迫的响应，这是一个相对未被探索的领域。通过受控气候室实验，我们研究了盐分胁迫如何影响根分泌物（REs）和根际土壤中 Fe（水合）氧化物和 SOC 之间的相互作用。我们的结果表明，30 ppt 的盐度显着增加了秋茄 REs 中糖、氨基酸、无机养分（NH、NO）和磷的释放，同时减少了结晶和无定形 Fe（水合）氧化物的含量，并增加了络合 Fe（水合）氧化物的含量，从而降低了根际土壤中它们的结晶度。重要的是，在高盐度（30 ppt）下，根际中的 Fe-OC 键表现出更大的稳定性，表明与原状土壤相比，对盐分胁迫的抵抗力更强。盐分胁迫还提高了 REs 中的碳氮（C/N）比。用不同 C/N 比的人工 REs（AREs）进行测试表明，与对照相比，在 C/N 比为 10 和 30 时，Fe（水合）氧化物的含量降低，而随着 C/N 比的增加，Fe-OC 的含量增加。引入 C/N 比为 20 的 AREs 显着影响了根际结晶 Fe（水合）氧化物和 Fe-OC 含量，突出了 AREs 对 Fe（水合）氧化物和 OC 结合的影响。土壤微生物的存在对于 Fe（水合）氧化物和 OC 的结合至关重要，因为灭菌土壤的 Fe（水合）氧化物和 Fe-OC 含量明显低于未灭菌土壤。这项研究表明，在盐分胁迫下，红树林植物通过影响 Fe（水合）氧化物的结晶度并促进稳定的 Fe-OC 配合物的形成，在稳定根际 SOC 方面发挥着关键作用，突出了植物 REs、盐分胁迫和土壤矿物质之间的复杂相互作用。
