Characteristics of natural habitats of an endangered species, <i>Cymbidium macrorhizon</i>

Background: A leafless, partially mycoheterotrophic terrestrial orchid Cymbidium macrorhizon is legally protected as Endangered Species in Korea, but there is insufficient information on the habitat and growth conditions of this species to ensure its conservation. We conducted a survey of the occurrence and growth of C. macrorhizon from June to November 2024 on Mt. Noza in Geoje, and in Jeju during July and September. We also examined the vegetation, canopy coverage, soil respiration rate, and soil physicochemical parameters in C. macrorhizon habitats. To understand the factors influencing the survival and reproductive success of C. macrorhizon, we analyzed the relationships between population size and the surrounding vegetation, as well as soil physicochemical parameters. Results: In both Geoje and Jeju, C. macrorhizon can be observed from late June to early November, with the highest emergence occurring in July. However, less than 3% of the fruits were continuously maintained and reached fruit maturity. Cymbidium macrorhizon was observed with more than 20 individuals in the Pinus thunbergii and Platycarya strobilacea communities. The results of the Principal Component Analysis indicated that the P. thunbergii community is associated with soil characteristics such as organic matter content, water content, and pH. The successful progression of C. macrorhizon through its growth stages, including flowering, fruiting, and fruit maturation, was primarily observed in areas with adequate light penetration, specifically where light levels reached up to a relative light intensity of 56% with a maximum of about 5,300 lux, rather than those excessively shaded by the canopy. Conclusion : s: Cymbidium macrorhizon forms large populations, especially in P. thunbergii stands, which are characterized by well-developed organic layers and well-drained soils with approximately 40% soil moisture content. It is proposed that C. macrorhizon may increase its population size through vegetative propagation via rhizomes facilitated by microbial activity in environments that limit population growth through seed reproduction, such as shaded stands with high organic matter content. Understanding the specific environmental conditions, such as soil characteristics and light penetration, and vegetation community in its natural habitat, can provide crucial data for establishing effective conservation strategies to ensure the continued survival and proliferation of C. macrorhizon.