Abstract: There are thousands of Phaius delavayi individuals, which mainly distributed in two different habitats, .i e. travertine areas and the remained forests, in Huanglong Valley, Sichuan, and the individual pollination successes were different between these two habitats. However, little is know about the causes and mechanisms leading to the differences. The differences of the microenvironmental conditions, morphological traits, male and female reproductive success of P.delavayi in two habitats were measured. The results showed that the microenvironmental conditions were found to be quite different between these two habitats, tree cover, soil depth, soil moisture, soil organic matter, total nitrogen, and relative air humidity were higher in forest areas, on the contrary, shrub cover, herb cover, moss cover, air temperature, relative light intensity, soil temperature, total calcium, and pH were higher in travertine areas. The results also showed that floral traits and reproductive success of P.delavayi had significant differences between these two habitats. The individuals in travertine areas had larger length and width of the largest leaf, more numbers of flowers within inflorescence, larger length of spur, and longer life span of both single flower and inflorescence than those in forest areas. However, both male and female reproductive successes were lower in travertine areas than those of that in forest areas. We supposed that the differences of temperature and light between two habitats may play important roles in leading to the differences of pollinia removal and nature fruit set of P.delavayi in the studied area.

Key words: habitat, Huanglong Valley, orchid species, pollination success, pollinator