Reintroduction of an epiphytic orchid: Plant size matters

Abstract

Orchidaceae is one of the largest family and among the most threatened in flowering plants. Approximately 70 % of orchid species grow epiphytically on trees or rock surfaces without attaching to soils, making them highly sensitive to environmental changes. However, little attention has been paid to the epiphytic nature of orchids and the limitations of water and nutrients in the epiphytic habitat in reintroduction practice. In the present study, Cymbidium tracyanum was selected to investigate the impact of plant size, nitrogen addition, and mycorrhizal fungi application on the survival of epiphytic orchids after reintroduction. After transplanting onto tree trunks for 14 months, a survival rate of over 80 % was achieved using large-sized seedlings, while all small-sized seedlings died within 2 months. The application of nitrogen and mycorrhizal fungus did not affect plant survival but led to an increase in nitrogen content in the leaves, which could be beneficial for future growth in nutrient-deficient habitats. The difference in plant-fungi association primarily occurred between before and after reintroduction, rather than different treatments in the reintroduction site. Additionally, the application of nitrogen and mycorrhizal fungus primarily impacted the presence of endophytic fungi, with a lesser effect on the richness, presence, and abundance of orchid mycorrhizal fungi. These findings highlight the significance of plant size in the reintroduction success of epiphytic orchids, with nitrogen and mycorrhizal fungal applications holding potential benefits for future plant growth.