Soil Organic Matter Composition in Coastal and Continental Date Palm Systems: Insights from Tunisian Oases

• Published in: Pedosphere Vol. 29; no. 4; pp. 444 - 456
• Main Authors: MLIH, Rawan K., GOCKE, Martina I., BOL, Roland, BERNS, Anne E., FUHRMANN, Irabella, BRAHIM, Nadhem
• Format: Journal Article
• Language: English
• Published: Beijing Elsevier Ltd 01-08-2019; Elsevier Science Ltd; Institute of Crop Science and Resource Conservation, University of Bonn, Bonn 53115 ,Germany; Agrosphere Institute(IBG-3), Forschungszentrum Jülich GmbH, Jülich 52428 ,Germany%Institute of Crop Science and Resource Conservation, University of Bonn, Bonn 53115 ,Germany%Agrosphere Institute(IBG-3), Forschungszentrum Jülich GmbH, Jülich 52428 ,Germany%Department of Geology, University of Tunis El Manar, Tunis 2092 ,Tunisia
• Subjects: amino sugar; Composition; Degradability; dryland; Fertilizers; Fungi; Magnetic resonance spectroscopy; microbial community; Microorganisms; Multilayers; NMR; Nuclear magnetic resonance; Oases; Organic fertilizers; Organic matter; Organic soils; Soil management; Soil microorganisms; Soil moisture; soil organic carbon; Soil organic matter; Soil temperature; Soils; solid-state NMR; subsoil amelioration; Sugar; Topsoil; total nitrogen; Vegetation; Vegetation cover; microbial community; solid-state NMR; dryland; subsoil amelioration; soil organic carbon; amino sugar; total nitrogen
• ISSN: 1002-0160; 2210-5107
• DOI: 10.1016/S1002-0160(19)60814-3

In Tunisia, the coastal Chenini oasis is characterized by a lush vegetation cover, whereas more inland continental oases (e.g., the Guettaya oasis) have a very scarce vegetation cover. For sustaining date palm production in these areas, organic fertilizers are applied, either spread on the soil surface (in Chenini) or buried under a sand layer (in Guettaya). We examined at a molecular level how these management techniques affect soil organic matter composition in oasis systems. A dominance of fresh plant input for Guettaya was indicated by solid-state 13C nuclear magnetic resonance spectroscopy signals, which was most pronounced in the uppermost soil close to palms. Evidence for more degraded organic matter was found in deeper soil near the palms, as well as in the soil distant from the palms. Amino sugar contents were low in the uppermost Guettaya soil near the palms. The overall microbial amino sugar residue contents were similar in range as those found in other dryland environments. With increasing distance from trees, the amino sugar contents declined in Guettaya, where the palms grow on bare soil, but this was not the case for Chenini, which has multi-layer vegetation cover under palms. In agreement with the results from previous dryland studies, the soil microbial community in both oasis systems was dominated by fungi in topsoil, and a shift toward bacteria-derived residues in subsurface soil. This might be due to higher variability of temperature and moisture in topsoil and/or lower degradability of fungal remains; however, further research is required to confirm this hypothesis.