Abstract:

Abstract: To determine orchid diversity along an elevation gradient, we conducted a four-year investigation at five management districts (Ruyang, Dadongshan, Chengjia, Longtanjiao and Tianjingshan) in Nanling National Nature Reserve, northern Guangdong Province. The orchid species and individual number, their life forms and habitat conditions were surveyed. Then we analyzed their floristic components and evaluated their endangerment degree according to the IUCN Red List Categories and Criteria (IUCN, 2001). To study the altitudinal distribution of orchids, we divided the study area from 230 m to 1,902 m into nine equal belts at 200-m intervals. We recorded 70 orchid species of 38 genera in total, of which 63 species were recorded in Ruyang. Most of these species had small populations. The orchid diversity presented a hump-shaped pattern along the elevational gradient with a peak at mid-elevations (600-800 m), of which terrestrial, epiphytic, and saprophytic orchids showed the same trend. The endangered species were mainly distributed at 600-1,000 m, where there were better habitats and less human disturbance. The most abundant floristic components were found at 800-1,000 m. The tropical orchids mainly distributed below 1,600 m. There was a higher similarity index between the neighbouring elevational belts. It was concluded that the abundant orchid species at mid-elevation resulted from better thermal and humidity condition, while the conspicuous decline of species richness at low elevation is a result of human disturbance.

Key words: orchids, species diversity, elevational gradient, floristic components, endangered categories