Quantifying the epiphytic orchid-host tree relationship in a Himalayan montane forest, central Nepal

Epiphytic orchids grow on host trees through a symbiotic relationship and are likely to be impacted by the characteristics and species of hosts.This study aims to explore the relationship between host trees and epiphytic orchids within the Panchase Forest Protection Area, central Nepal.The data were collected through a biophysical survey using a stratified random sampling method.The forest area was classified into three elevation zones: 1,000-1,500 m, 1,500-2,000 m, and 2,000-2,500 m using a 30 m SRTM dataset for accurate elevation data.A total of 40 sampling plots were established to examine the dynamics of host trees and epiphytic orchids across varying elevations and aspects.The diameter at breast height (DBH), height, and bark roughness of host trees, the distance from settlements, and the vertical distribution of orchids on host trees were recorded.Altogether, 51 epiphytic orchids were documented in 23 host trees.A considerable relationship between orchid species diversity and host tree diversity, as well as proximity to human settlements, was found.Host size, measured by height and DBH, had a significant influence on the distribution of orchid species.A positive correlation was observed between the number of orchid species and both the number of host species (p = 0.042) and the distance from human settlements (p = 0.045).Our findings show that large trees support more epiphytic orchids, and disturbances to them reduce orchid diversity.Finally, protecting host trees is crucial for conserving epiphytic orchid habitats and ensuring the survival of these ecologically important species.