Abstract: Asian tropical rainforests have suffered tremendous damages due to the cultivation of commercial plantations, which have resulted in severe species losses, including of the Dipterocarpaceae family. Dipterocarps like Hopea hainanensis and Hopea reticulata are now listed as endangered in the international union for conservation of nature (IUCN) Red List, and Vatica mangachapoi is classified as vulnerable. Reintroduction of the threatened plant species by their artificial planting in an original habitat has been widely recognized as effective to recover the threatened species. However, current reintroductions are mostly based on mono-cultures and also short-term which in turn cannot restore natural recruitment, genetic diversity and functional traits of the threatened species. Here, we have addressed this challenge in a > 32 year-long reintroduction program in the rubber plantations in Southern China. Saplings (5000 − 10,000) of the three threatened Dipterocarp species (H. hainanensis, V. mangachapoi, and H. reticulata) were mix-planted with 99 other species, which originally coexisted naturally in this habitat, in the understory of the rubber plantations in Hainan Island. After 32 years, satellite images show a complete transformation of the landscape. Further, the field surveys have revealed that H. hainanensis and V. mangachapoi have successfully recovered as their numbers have now reached to 115,780 and 108,300, respectively. Most of their reintroduced saplings have survived, and the restored forest has further engaged in natural recruitment. Genetic diversity analysis with ddRADSeq and investigations of several functional traits also support the above inferences. Our long-term mix-plantations not only presents the first case of successful recovery of natural recruitment, genetic diversity and functional traits of the threatened Dipterocarps in China, it also provides a framework for restoring threatened species in other plantations throughout the globe.

Key words: Active restoration, Hopea hainanensis, Reintroduction, Rubber plantation, Threatened Dipterocarpaceae, Vatica mangachapoi