Objective To study the differences between C，N and P contents and their ecological stoichiometry ratios of different organs of different coastal tree species under drought stress，and to reveal the physiological adaptation mechanism and nutrient cycling law of different coastal sandy afforestation tree species to drought stress. Method One-year-old C. equisetifolia，E. urophylla × E. grandis，A. mangium × A. auriculiformis and A. melanoxylon seedlings were used as research objects，and control，mild，moderate and severe treatments were set.to explore the ecological stoichiometry of C，N and P of different coastal tree species under drought stressd. Result Tree species，organs，drought stress degree，pairwise interaction and joint interaction have significant effects on C，N and P content and their stoichiometric ratios（PC.equisetifolia will conserve water by increasing the distribution of leaf N；E.urophylla × E.grandis increase the use efficiency of N and P in leaves，and slow down its growth rate by increasing the C content per unit mass of leaves；under severe drought stress，A.mangium × A.auriculiformis will decrease the P content of the whole plant and increase the N use efficiency of the whole plant；under different drought stress severities，P accumulation was present in the stems of A.melanoxylon.Correlation analysis shows：drought stress affects the physiological and metabolic activities of plants，resulting in the decoupling of various elements.The distribution of C in different organs of each tree species is small，while the distribution of N and P is quite different，therefore，the change of ecological stoichiometry ratio of each organ is mainly related to the change of N and P content.The absorption of N and P by roots is conducive to the assimilation and redistribution of C by leaves. Conclusion C. equisetifolia can conserve water by increasing the allocation of N content in leaves under drought stress，and its growth is relatively limited by P elements.A. mangium × A. auriculiformis and A. melanoxylon have higher organic matter accumulation capacity and stronger ability to resist adverse external environments；E. urophylla × E. grandis has low N and P utilization efficiency，because it does not have the ability of biological nitrogen fixation，its growth is mainly limited by N，and it is necessary to pay attention to the application of nitrogen fertilizer or mix with nitrogen-fixing tree species during afforestation.
MAO et al. (Wed,) studied this question.