Soil-Easily Extractable Glomalin: An Innovative Approach to Deciphering Its Molecular Composition under the Influence of Seasonality, Vegetation Cover, and Wildfire

11 páginas.- 7 figuras.- 3 tablas.- 67 referencias.- The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.est.4c10036

Easily extractable glomalin (EEG) is a fraction of soil organic matter thought to contain mainly glomalin-related soil glycoproteins produced by mycorrhizal fungi. The EEG has an impact on various soil ecological functions, primarily related to soil aggregation formation and stability as well as water repellence. Here, analytical pyrolysis–gas chromatography/mass spectrometry (Py-GC/MS) was used for studying the molecular composition of soil EEG, and a detailed description of the chemical composition is reported. Samples extracted from Mediterranean soils under different vegetation covers (Pinus halepensis and shrubland species, Rosmarinus officinalis, and Brachypodium spp, predominantly), impacted or not by forest fires and collected at different times, were studied. A total of 139 compounds were identified and grouped based on their probable biogenic origin. The EEG chemical composition is dominated by lipids, aromatic compounds, steranes, and hydroaromatics with a remarkable abundance of compounds from plant origin. Significant EEG structural changes can indicate environmental disturbances such as those after a wildfire. The EEG soil organic fraction is found to be a stable and heat-resistant material in nature if soil temperatures remain below 200–250 °C. This study advances the understanding of EEG by providing a detailed molecular characterization and highlighting its role as a stable, heat-resistant component of soil organic matter in Mediterranean ecosystems. The main findings indicate that while EEG is structurally resilient and mostly originates from plant material, its composition is more similar to that of humic acids than to that of glycoproteins.

Layla M. San Emeterio thanks the Foundation for Science and Technology (FCT), Portugal for the postdoctoral contract EURAXESS offer IR 145344. This work was partly supportedby the EROFIRE project (PCIF/RPG/0079/2018) funded bythe FCT and by the FIRE2C project (CNS2023-143750) funded by MICIU. N.T. Jiménez-Morillo acknowledges the“Ramón y Cajal” contract (RYC2021-031253-I) funded by MCIN/AEI/10.13039/501100011033 and the European Union “NextGenerationEU”/PRTR.

Peer reviewed