Analytical Pyrolysis of Soil Easily-Extractable Glomalin (EEG) fraction.

Easily Extractable Glomalin (EEG) represents an organic fraction of the soil that contains mainly glomalin-related soil proteins (GRSP), a glycoprotein abundantly found in soils produced by arbuscular mycorrhizal fungi in the phylum Glomeromycota [1]. The EEG fraction is confirmed to have multiple ecological functions in soils, including the improvement of soil stability and resilience to degradation, facilitate aggregate formation and contribute to soil carbon storage [2]. Given its potential for soil C immobilization, a detailed molecular characterization "fingerprint" of pyrolysis products of EEG fraction extracted from a Mediterranean soil under different plant covers, affected and unaffected by forest fire and at different times is conducted. A total of 16 samples were extracted from soils in Gorga (NE Alicante, Spain). Further information about the sampling process and EEG extraction protocols are described elsewhere [3]. In short, samples were taken from the surface (to 2.5 cm depth; A horizon) under pine and shrub covers, immediately after a forest fire (July 2011), and at 4, 8 and 12 months after the fire. Surrounding soils with similar characteristics but unaffected by fire were taken as control. The EEG samples were analysed using pyrolysis-gas chromatography coupled to mass spectrometry (Py-GC/MS). Pyrolysis temperature was 400 ºC for 1 minute and detailed chromatographic conditions and compound assignment procedure were as described in [4]. A total of 139 compounds were identified and grouped according to their probable biogenic origin: polysaccharides (PS), lignin and polyphenols (LIG), proteins and polypeptides (PRO), non-specific aromatic compounds (ARO), hydro-aromatics (HAR), lipids (LIP), polycyclic aromatic hydrocarbons (PAH) and terpenes (TER). A remarkable high similarity was found between EEG samples from different plant covers, both affected and unaffected by forest fire and at different time over a year after the fire. This fact indicates th
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