To investigate the effects of trunk girdling on Cunninghamia lanceolata semi-natural forests in Hainan Tropical Rainforest National Park after 16 months,and to explore techniques for ecological restoration through the rapid transformation of planted forests into natural forests,representative 32-year-old Cunninghamia lanceolata semi-natural forests were selected as experimental stands within the general control area of the park. The trees in the experimental stands (excluding control plots) were subjected to girdling. The species composition and diversity characteristics were analyzed using major dendrometric factors,importance values,and diversity indices. The results revealed that 90% of the Cunninghamia lanceolata trees across the three semi-natural forests perished and transformed into snags 16 months after trunk girdling. The dominant living trees in both the arbor and shrub layers post-girdling primarily consisted of naturally regenerated native species that were present in the pre-girdling semi-natural forests. The arbor layer exhibited an ingrowth of 128,220,and 85 trees per hectare,respectively,while the shrub layer showed an ingrowth of 416,115,and 115 shrubs per hectare,correspondingly. Trunk girdling did not cause damage or mortality to the natural trees in the arbor layer and only minimally affected those in the shrub layer. Arbor layer species richness was recorded as 82,77,and 56,with Shannon-Wiener indices of 5.68,5.27,and 5.07,respectively. The importance value of Cunninghamia lanceolata trees decreased to less than 10%,with the evergreen arbor species among naturally regenerated native trees contributing 69.0%,67.9%,and 68.3% of the importance value. In the shrub layer,species richness counts were 169,112,and 99,accompanied by Shannon-Wiener indices were 4.84,5.36,and 5.63,respectively. Meanwhile,evergreen arbor species constituted 42.0%,54.8%,and 62.8% of the importance value. Following 16 months of trunk girdling,the Cunninghamia lanceolata semi-natural forests successfully transitioned into natural forests of the zonal vegetation type,characterized by extremely rich species diversity and the presence of a considerable number of rare or high-value tree species. This serves as a typical case study for the transformation of Hainan tropical rainforest plantations into natural forests. Trunk girdling is one of the crucial ecological restoration techniques enabling the rapid transformation of qualified planted forests into natural forests in Hainan's tropical rainforest national parks.