Impact of proximity to a pathway on orchid pollination success in Huanglong National Park, South-West China

Although edge effects often significantly alter abiotic habitat variables, and the performance and behaviour of plant and animal species, they are rarely taken into account when designing nature reserves or managing the movement of visitors within reserves. In this study, we examined the effects of proximity to a habitat edge, created by a visitor pathway, on reproductive success of the orchids Phaius delavayi and Ponerorchis chusua within the Huanglong National Park, China. Parallel transects were established at different distances from the pathway to test the effects of proximity to the pathway on male and female reproductive success in two consecutive years. For Phaius delavayi, percentage pollinarium removal and percentage fruit set showed significant variation between transects in both years, with plants in transects closer to the pathway having lower reproductive success. P. chusua showed the same trends except for pollinarium removal in one year. These results are consistent with the hypothesis that proximity to the pathway, which is used by a large number of visitors every day throughout the orchids¿ flowering seasons, interfered with pollinator activity, depressing male and female reproductive success in both species. The impacts on reproductive success were significant for plants within approximately 10 meters of the pathway. Such edge effects may be common, and may need to be considered when designing nature reserves in which visitor activity is encouraged.