The population dynamic of Pleione formosana at Alishan area in Taiwan

Background/Question/Methods:  Pleione formosana is a renowned orchid in the world, and its key feature is one bulb only growing with one leaf. It mostly accompanies with bryophytes on the surface of rocky cliffs in montane cloud forest which altitude is between 700 to 2,500 m in Taiwan. Previous long-term survey has showed that the individuals of Pleione formosana were decreasing and it was also classified to vulnerable species in IUCN Red List, so the conservation and the regular monitoring is absolutely necessary. Therefore, we set 40 1x1m quadrats at Alishan area in order to understand the dynamics of Pleione formosana in Taiwan. In addition, trying to figure out what kind of the environmental factors affect the population growth. We surveyed the numbers of Pleione formosana monthly during 2011-2012 and 2016-2017. The herb coverage, bryophyte coverage, and canopy openness were recorded seasonally and used multivariate analysis of variance (MANOVA) to know which the environmental factors had seriously effect on Pleione formosana.

Results/Conclusions:  The results showed that the population ranged from 343 to 1,285 in 2011-2012, while the overall population declined almost 200 individuals in the recent year. Most of the individuals increased simultaneously with both sexual and asexual reproduction during April to July, but lots of the individuals could not be found in winter due to the winter dormancy. We also discovered that some quadrats had more individuals with the 30-56% bryophyte coverage and the 13-21% canopy openness. According to this result, we surmised that Pleione formosana prefers to survive in the moist and shady environment. Consequently, the total population of Pleione formosana varied monthly and yearly as the environmental factors change. How will Pleione formosana respond to the rapid climate change in the future? We need more long-term monitoring to understand the dynamic and the most important factors of Pleione formosana in Taiwan.