摘要
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.
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.
基金
the German Federal Ministry of Education and Research(Bundesministerium für Bildung und Forschung,BMBF)for the Exploratory Grant(No.STC TUNGER-006/INTOASES)as a part of the Bilateral Scientific and Technological Cooperation between the Republic of Tunisia and the Federal Republic of Germany
the patience and hospitality of the oasis farmers at Chenini and Guettaya oases in Tunisia,as well as technical support by the technicians at the Institute of Crop Science and Resource Conservation of the University of Bonn and the Agrosphere Institute(IBG-3)of Forschungszentrum Jülich GmbH,Germany
