Abstract:

Canopy-dwelling epiphytes and their associated dead organic matter are important floristic, structural and functional components in montane moist forests. Because of the difficulties related to access, the biodiversity and ecosystem-level functional attributes of epiphytes have received little attention in forests. With an increase in our understanding of epiphytic biodiversity and their roles in ecosystem-level interactions, combined with improved access to the forest canopy, studies on epiphytic organisms in forest canopies have progressed from the individual level to the ecosystem level. Biodiversity and biomass of epiphytes and their functional roles at the ecosystem-level are becoming a hot topic of recent study. Recent work in tree canopies in a variety of forest types, however, has pointed out that the role of epiphytes in ecosystem-level interactions are more important than previously thought due to their anatomical, morphological, and physiological characteristics. Considerable research conducted worldwide has shown that the forest canopy is a favorable habitat supporting a much richer epiphytic flora than previously thought. It was estimated that there are 29 500 epiphytic species, including 24 000 vascular epiphytes that account for 10% of the total vascular species in the world. There are large differences in the epiphytic biomass of forests worldwide ranging from 105-44 000 kg·hm^-2. The biomass of epiphytic material of forest canopies was greater than the leaf biomass of host trees in some old growth forests. Epiphytes have a tremendous leaf area index (LAI). Epiphytes play an important role in biodiversity, water and nutrient cycling in forest ecosystems, and are sensitive indicators of environment change, due to rich species, high biomass and special morphological traits and their position at the forest-atmosphere interface. The epiphyte community also provides a source of food and habitat for a variety of birds, mammals, amphibians, reptiles, and insects.

Species composition, growth and distribution of epiphytes are influenced by environmental factors and human disturbance. Research on epiphytes in forest canopies still is very active due to a lack of field data at the ecosystem level for a lot of forest types under different environmental conditions in many regions. International forest canopy networks have been established worldwide. To understand the relationship among community characteristics, environmental factors and epiphyte dynamics, and develop effective and standard methods and technologies for the study of forest canopies, more work is needed in this field. In China, there has been very little work on the ecology of epiphytes in forest canopies, and this remains a challenging and fruitful area for future research.

Key words: Forest canopy, Epiphytes, Species diversity, Biomass, Ecological functions, Environmental factors