参考沿海防护林高盐低磷的实际情况，设置0(N0)、2(N1)、4(N2)、6(N3)和8(N4) g·kg^-1NaCl 5个单一处理组以及N2-P1〔0.5 g·kg^-1Ca(H₂PO₄)₂〕、N2-P2〔1.5 g·kg^-1Ca(H₂PO₄)₂〕、N3-P1、N3-P2、N4-P1和N4-P2 6个复合处理组，研究不同浓度NaCl单一胁迫及NaCl胁迫下施磷对台湾相思（Acacia confusa Merr.）幼苗干物质积累、根形态及营养元素含量的影响。结果显示：总体上看，NaCl单一胁迫及低浓度（4 g·kg^-1）NaCl胁迫下施磷均会明显减少台湾相思幼苗根干质量、总干质量、总根长、总根表面积和总根体积；中浓度（6 g·kg^-1）NaCl胁迫下施磷对幼苗干物质积累和根形态的改善效果不显著，但施1.5 g·kg^-1 Ca(H₂PO₄)₂后幼苗根干质量和总干质量高于NaCl单一胁迫。从不同级别根直径（D）看，低径级（0.0 mm＜D≤0.5 mm）的根对NaCl单一胁迫较为敏感，且在低浓度NaCl胁迫下施磷后受抑制更加明显；而高径级（D＞5.0 mm）的根对NaCl单一胁迫有一定抗性，中浓度NaCl胁迫下施磷后的总根长、总根表面积和总根体积明显高于NaCl单一胁迫。与对照〔0 g·kg^-1NaCl，0.0 g·kg^-1Ca(H₂PO₄)₂〕相比，NaCl单一胁迫及NaCl胁迫下施磷会使根中Na含量明显增加，其他7种元素含量总体下降。高浓度（8 g·kg^-1）NaCl胁迫导致幼苗死亡，而施磷后幼苗对NaCl胁迫有一定的抵抗作用，其中以施0.5 g·kg^-1Ca(H₂PO₄)₂的效果较好。相关性分析结果显示：NaCl单一胁迫下台湾相思幼苗根中P含量与总根长、根尖数、根分枝数和根组织密度呈显著或极显著正相关，与平均根直径呈显著负相关；NaCl胁迫下施磷后幼苗根中Mn和K含量与根干质量、总干质量、总根长、总根表面积和总根体积均呈显著或极显著正相关。综上所述，在沿海种植台湾相思幼苗时，建议低盐土壤不施磷，中高盐土壤可根据具体土壤盐胁迫程度添加磷，同时适量添加Mn和K。

Considering the actual situation of high salt and low phosphorus of coast protection forest, five single treatment groups namely 0 (N0), 2 (N1), 4 (N2), 6 (N3), and 8 (N4) g·kg^-1 NaCl and six combined treatment groups namely N2-P1 〔0.5 g·kg^-1Ca(H₂PO₄)₂〕, N2-P2 〔1.5 g·kg^-1Ca(H₂PO₄)₂〕, N3-P1, N3-P2, N4-P1, and N4-P2 were set in this study, effects of NaCl single stress at different concentrations and phosphorus application under NaCl stress on dry matter accumulation, root morphology, and nutrient element contents of Acacia confusa Merr. were studied. The results show that on the whole， NaCl single stress and phosphorus application under low concentration (4 g·kg^-1) NaCl stress will evidently decrease root dry mass, total dry mass, total root length, total root surface area, and total root volume of A. confusa seedlings; the improved effect of phosphorus application under medium concentration (6 g·kg^-1) NaCl stress on dry matter accumulation and root morphology of seedlings is not significant, but the root dry mass and total dry mass of seedlings after applying 1.5 g·kg^-1 Ca(H₂PO₄)₂ are higher than those under NaCl single stress. From the different levels of root diameter (D), roots in low diameter class (0.0 mm＜D≤0.5 mm) are relatively sensitive to NaCl single stress, and are more evidently suppressed after phosphorus application under low concentration NaCl stress; while roots in high diameter class (D＞5.0 m) possess some resistance to NaCl single stress, total root length, total root surface area, and total root volume after phosphorus application under medium concentration NaCl stress are obviously higher than those under NaCl single stress. Compared with the control 〔0 g·kg^-1 NaCl， 0.0 g·kg^-1 Ca(H₂PO₄)₂〕, NaCl single stress and phosphorus application under NaCl stress will evidently increase Na content in roots, while contents of the other seven elements decrease in general. High concentration (8 g·kg^-1) NaCl stress causes seedling death, while seedlings are partially tolerant to NaCl stress after phosphorus application， in which， the effect of applying 0.5 g·kg^-1 Ca(H₂PO₄)₂ is better. The correlation analysis result shows that P content in roots of A. confusa seedlings shows significant or extremely significant positive correlations with total root length， number of root tip， number of root branch， and root tissue density under NaCl single stress, and shows a negative correlation with average of root diameter; both Mn and K contents in roots of seedlings after phosphorus application under NaCl stress show significant or extremely significant positive correlations with root dry mass, total dry mass, total root length, total root surface area, and total root volume. In conclusion, it is suggested to apply phosphorus according to the specific soil salt stress degree in medium and high salt soil and supplement suitable amount of Mn and K but not apply phosphorus in low salt soil when planting A. confusa seedlings in coastal areas.