Spatial patterns of two epiphytic Bird's-nest ferns in a Moist Subtropical Forest, Northern Taiwan

The aerial micro-habitats created by bird's-nest ferns provide invertebrate habitats that are distinct from the forest-floor environment, and they contribute to the biological diversity of tropical and subtropical forests. In this study, we set up and surveyed a 3.84-ha sample area in the Fushan Forest Dynamics Plot, which is located in a subtropical moist forest in northern Taiwan. We analyzed the spatial distributions of 2 native bird's-nest ferns, Asplenium antiquum and A. nidus, to explore how topography and structural factors of host trees, which strongly affect the light conditions and water availability, shape the spatial distributions of these 2 species. The distributions of these 2 bird's-nest ferns were mostly concentrated in downhill areas and near creeks with higher water availability. In terms of the epiphytic locations on host trees, the 2 bird's-nest ferns were mostly attached to the trunk of host trees rather than to the branches in the canopy. The epiphytic height of both species was concentrated at 2∼4 m above the ground, and they rarely grew at a height of >10 m above the ground. The spatial distribution characteristics of A. antiquum and A. nidus were similar. Even in the Fushan subtropical humid forest where drought events are rare, A. antiquum and A. nidus were mostly distributed in downhill areas and near creeks with relatively high water availability and on the lower trunks of host trees with low light levels. The roles of photosynthesis, water physiological characteristics, and typhoon disturbances to the forest canopy in affecting the spatial patterns of bird's-nest ferns in this subtropical moist forest are also discussed. © 2021 Taiwan Forestry Research Institute. All rights reserved.