Iron (Fe) oxides play an important role in maintaining soil organic carbon (SOC) stability. However, little attention has been paid to the role of Fe oxides in preserving SOC in mangrove wetlands with different vegetation communities. In this study, four soils of dominant vegetation communities: Phragmites australis (PA), Acanthus ilicifolius (AI), Sonneratia apetala (SA), and mixed soils of S. apetala and A. ilicifolius (SA + AI) were selected from mangrove wetland of Qi'ao Island. The distributions of Fe‐bound organic carbon (OC‐Fe) and Fe oxides (Feo, acid oxalate‐extractable Fe; Fep, pyrophosphate‐extractable Fe), and the role of soil factors in SOC conservation were investigated. The results showed that soil OC‐Fe content ranged from 1.03 to 4.96 g/kg, with a contribution to SOC ranging from 5.97% to 24.07%, which was highest in SA + AI (3.58 ± 0.94 g/kg), followed by PA (2.67 ± 1.07 g/kg), SA (1.88 ± 0.43 g/kg), and AI (1.82 ± 0.32 g/kg). The Fep content was higher in the PA and SA + AI, however, the Feo content was lower. Structural equation modeling indicated that SOC, Feo, and Fep were direct drivers of OC‐Fe formation. Overall, the aboveground biomass of different vegetation communities indirectly affected the OC‐Fe content by regulating SOC inputs. High water contents, low oxygen conditions, and near‐neutral soils in mangrove wetlands favor OC‐Fe formation between Fe oxides and SOC by co‐precipitation or complexation. This study highlights the importance of mangrove wetland vegetation communities in Fe‐C coupling, while providing theoretical support for the study of carbon cycling processes in mangrove wetlands.

中文翻译：

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铁在红树林湿地不同植被群落下土壤有机碳稳定中的作用


铁 （Fe） 氧化物在维持土壤有机碳 （SOC） 稳定性方面起着重要作用。然而，很少有人关注铁氧化物在保持具有不同植被群落的红树林湿地土壤有机碳中的作用。本研究从七岱岛红树林湿地中筛选出 4 种优势植被群落土壤：芦苇 （PA）、苇苣 （AI）、花瓣松 （SA） 以及花苔苑和蒲苇混交土 （SA + AI）。Fe 结合有机碳 （OC-Fe） 和 Fe 氧化物（Feo，酸性草酸盐可萃取 Fe;研究了 Fep、焦磷酸盐可萃取的 Fe） 以及土壤因子在 SOC 保护中的作用。结果表明：土壤OC-Fe含量为1.03—4.96 g/kg，对土壤有机碳的贡献为5.97%—24.07%，其中SA+AI最高（3.58±0.94 g/kg），其次是PA（2.67±1.07 g/kg）、SA（1.88 ± 0.43 g/kg）和AI（1.82 ± 0.32 g/kg）。PA 和 SA + AI 中的 Fep 含量较高，而 Feo 含量较低。结构方程模型表明 SOC、Feo 和 Fep 是 OC-Fe 形成的直接驱动因素。总体而言，不同植被群落的地上生物量通过调节 SOC 输入间接影响 OC-Fe 含量。红树林湿地的高含水量、低氧条件和近中性土壤有利于 Fe 氧化物和 SOC 之间通过共沉淀或络合形成 OC-Fe。本研究强调了红树林湿地植被群落在 Fe-C 耦合中的重要性，同时为红树林湿地碳循环过程的研究提供了理论支持。