Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, North Carolina, USA.
College of Resource and Environmental Sciences, Nanjing Agricultural University, Nanjing, China.
Glob Chang Biol. 2023 Oct;29(20):5941-5954. doi: 10.1111/gcb.16886. Epub 2023 Jul 25.
Soil organic carbon (C) is the largest active C pool of Earth's surface and is thus vital in sustaining terrestrial productivity and climate stability. Arbuscular mycorrhizal fungi (AMF) form symbioses with most terrestrial plants and critically modulate soil C dynamics. Yet, it remains unclear whether and how AMF-root associations (i.e., mycorrhizae) interact with soil minerals to affect soil C cycling. Here we showed that the presence of both roots and AMF increased soil dissolved organic C and reactive Fe minerals, as well as litter decomposition and soil CO emissions. However, it reduced mineral-associated C. Also, high-resolution nanoscale secondary ion mass spectrometry images showed the existence of a thin coating (0.5-1.0 μm thick) of Fe O (Fe minerals) on the surface of C N (fungal biomass), illustrating the close physical association between fungal hyphae and soil Fe minerals. In addition, AMF genera were divergently related to reactive Fe minerals, with Glomus being positively but Paraglomus and Acaulospora negatively correlated with reactive Fe minerals. Moreover, the presence of roots and AMF, particularly when combined with litter addition, enhanced the abundances of several critical soil bacterial genera that are associated with the formation of reactive minerals in soils. A conceptual framework was further proposed to illustrate how AMF-root associations impact soil C cycling in the rhizosphere. Briefly, root exudates and the inoculated AMF not only stimulated the decomposition of litter and SOC and promoted the production of CO emission, but also drove soil C persistence by unlocking mineral elements and promoting the formation of reactive minerals. Together, these findings provide new insights into the mechanisms that underlie the formation of reactive minerals and have significant implications for understanding and managing soil C persistence.
土壤有机碳 (C) 是地球表面最大的活跃碳库，对于维持陆地生产力和气候稳定性至关重要。丛枝菌根真菌 (AMF) 与大多数陆地植物形成共生关系，对土壤 C 动态具有关键的调节作用。然而，AMF-根系（即菌根）与土壤矿物质相互作用以影响土壤 C 循环的方式和程度仍不清楚。本研究表明，根系和 AMF 的存在均会增加土壤溶解有机碳和反应性铁矿物质，以及凋落物分解和土壤 CO 排放。然而，它会减少与矿物质结合的碳。此外，高分辨率纳米二次离子质谱图像显示，在 C N（真菌生物量）的表面存在一层 0.5-1.0 μm 厚的 Fe O（铁矿物质）薄涂层，说明真菌菌丝和土壤铁矿物质之间存在紧密的物理联系。此外，AMF 属与反应性铁矿物质呈显著的负相关，Glomus 与反应性铁矿物质呈正相关，而 Paraglomus 和 Acaulospora 则呈负相关。此外，根系和 AMF 的存在，特别是与添加凋落物相结合时，会增强与土壤中反应性矿物质形成相关的几个关键土壤细菌属的丰度。进一步提出了一个概念框架来说明 AMF-根系关联如何影响根际土壤 C 循环。简而言之，根系分泌物和接种的 AMF 不仅刺激凋落物和 SOC 的分解，促进 CO 排放的产生，还通过释放矿物质元素和促进反应性矿物质的形成来驱动土壤 C 的持久性。这些发现为理解和管理土壤 C 持久性提供了新的思路。
