| Summary: | Soil salinization, an important and increasingly prevalent issue in arid regions, influences plant growth and carbon (C): nitrogen (N): phosphorus (P) stoichiometry patterns by limiting nutrient access. Plant C:N:P stoichiometry patterns and response to soil salinity among organs (e.g., leaves, stems and roots) reflect plants’ trade-offs between access to resources and their adaptation strategies to different habitats. Common in marshes of arid middle-lower reaches of the Shule River Basin, China, Phragmites australis (Cav.) Trin. Ex Steud. (P. australis), is often the dominant species. The effects of soil salinity on the C:N:P stoichiometry among organs of P. australis were investigated in this study. The average N and P concentrations in leaves (19.09 ± 0.63 and 0.98 ± 0.05 g·kg−1, respectively) were significantly greater than those in roots (3.16 ± 0.16 and 0.76 ± 0.05 g·kg−1, respectively) and stems (3.80 ± 0.16 and 0.55 ± 0.05 g·kg−1, respectively) (P < 0.05). However, the average C concentrations in leaves (406.47 ± 5.37 g·kg−1) were not significantly different from those in stems (405.63 ± 6.03 g·kg−1) and roots (402.83 ± 7.94 g·kg-1) (P > 0.05). The N:P ratio in leaves (20.89 ± 0.81) was significantly greater than those in stems (8.95 ± 0.67) and roots (5.11 ± 0.49), while C:N and C:P ratios (22.33 ± 0.82 and 469.25 ± 26.81, respectively) were significantly lower than those in stems (114.56 ± 4.93 and 1014.49 ± 86.57, respectively) and roots (144.58 ± 8.25 and 693.00 ± 74.18, respectively) (P < 0.05). N and P concentrations of leaves and C concentration of stems under high soil salinity were significantly lower than those in low and medium soil salinity, whereas C:P and N:P ratios of leaves and C:P ratio of stems were significantly greater than the others (P < 0.05). Soil salinity played a dominant role in determining leaf’s and root’s C:N:P stoichiometry of P. australis. This indicated that plant in arid marshes adapt to soil salinity conditions by modulating the changes in solute penetration in leaves and roots. These lead to diverse stoichiometric response patterns of C:N:P stoichiometry among organs. The information helps to understand C:N:P stoichiometry patterns, nutrient utilization strategy and carbon allocation of dominant plants and its potential responses to global changes in the marsh wetland ecosystems of arid regions.
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