Effects of nebkhas succession on the stoichiometry in organs of Nitraria tangutorum and soils.

We analyzed the stoichiometry of carbon, nitrogen, and phosphorus in different organs of Nitraria tangutorum (roots, stems, and leaves) and soil across four succession stages in nebkhas in the desert-oasis ecotone: initial, developing, stable, and declining. The results showed that soil organic carbon, total nitrogen, total phosphorus, C:N, and C:P all peaked at the stable stage and then decreased, with reductions ranging from 25.9% to 64.9%, while the N:P was highest at the declining stage, increasing by 42.8% relative to the initial stage. Across all stages, leaf N and P contents were significantly higher than those in stems and roots. As succession progressed, stem and root C contents first increased and then decreased, peaking at the developing stage, with respective increases of 13.3% and 27.7%. Leaf and stem N contents were highest at the stable stage, with increases of 26.0% and 12.3%, respectively. Root N content declined by 40.7%. Stem and root P contents were lowest at the stable stage but rebounded significantly at the declining stage, increasing by 34.2% and 34.5%, respectively. The C:N and C:P of roots and stems initially increased and then decreased, peaking at either the developing or stable stages. In contrast, leaf C:N showed a gradual decline, leaf C:P first decreased and then increased, and leaf N:P gradually increased with succession. Multivariate analyses indicated that nebkha succession positively regulated soil physi-cochemical properties and root stoichiometric characteristics, while indirectly negatively regulating those of stems and leaves, thereby driving the plant-soil system away from nutrient accumulation toward depletion, and shifting nutrient limitation status from N limitation to N and P co-limitation.