Investigating the Impact of Salinity on Soil Organic Matter Dynamics Using Molecular Biomarkers and Principal Component Analysis

Abderrhamen Akkacha, Abdelkader Douaoui, Khaled Younes (), Christina El Sawda, Hatem Alsyouri, Samer El-Zahab and Laurent Grasset ()
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Abderrhamen Akkacha: Laboratory “PRAVDURN” (UKHM), Faculty of Nature and Life Sciences, (Algeria) Agricultural Production and Sustainable Valorization of Natural Resources, Hassiba Benbouali University of Chlef, Chlef 02180, Algeria
Abdelkader Douaoui: Laboratory Management and Valorization of Agriculture and Aquatic Ecosystems (LMVAAE), University Center of Tipaza, Tipaza 42000, Algeria
Khaled Younes: College of Engineering and Technology, American University of the Middle East, Egaila 54200, Kuwait
Christina El Sawda: College of Engineering and Technology, American University of the Middle East, Egaila 54200, Kuwait
Hatem Alsyouri: College of Engineering and Technology, American University of the Middle East, Egaila 54200, Kuwait
Samer El-Zahab: College of Engineering and Technology, American University of the Middle East, Egaila 54200, Kuwait
Laurent Grasset: Institut de Chimie des Milieux et Matériaux de Poitiers IC2MP, Université de Poitiers, UMR CNRS 7285, Equipe Eaux, Biomarqueurs, Contaminants Organiques, Milieux, B27, 4 rue Michel Brunet, CEDEX 9, 86073 Poitiers, France

Sustainability, 2025, vol. 17, issue 7, 1-21

Abstract: Soil salinity is a growing threat to agricultural sustainability, particularly in arid and semi-arid regions. Understanding how salinity affects soil organic matter (OM) is critical for improving land management and maintaining soil health. This study addresses these challenges by exploring the molecular-level impact of salinity on OM dynamics. Salinity exerts a depth-dependent influence on lignin and microbial lipid biomarkers, which are used to trace plant inputs and microbial activity, respectively. For lignin biomarkers, in the surface layer (0–20 cm), higher salinity levels are associated with increased Syringyl/Vanillyl (S/V) and Cinnamyl/Vanillyl (C/V) ratios, suggesting enhanced preservation of syringyl (S) and cinnamyl (C) units. In the middle layer (−20 to −60 cm), higher salinity correlates with elevated SVC (total lignin phenols), Acid/aldehyde (Ad/Al) ratios, and other markers of selective lignin degradation. For lipid biomarkers, salinity modulates microbial adaptation and turnover, as seen in variations in i17 (iso-C17), a17 (anteiso-C17), and unsaturation indices such as C16:1/C16, reflecting Gram-positive and Gram-negative bacterial activity. These trends indicate that salinity stress alters microbial lipid profiles, leading to reduced turnover and enhanced preservation in deeper, more anoxic environments. Principal Component Analysis (PCA) revealed depth- and salinity-driven patterns that distinguish between surface microbial transformations and deep-layer molecular preservation. Correlation analysis of Principal Components (PCs) with salinity revealed that higher salinity favored molecular stability in deeper layers, while lower salinity was associated with microbial transformations in surface layers. These findings underscore salinity’s critical role in OM stabilization and turnover, and provide a molecular framework to guide sustainable management of saline soils.

Keywords: soil organic matter dynamics; soil salinity; molecular biomarkers; lignin and lipids; Principal Component Analysis (PCA); sustainable soil management (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2025
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