Exploring epiphyte recruitment by means of time-space phorophyte gradients

A dynamic comprehension of the phorophyte and the environment it is creating is an important element in the understanding of epiphytic life. Distribution of epiphytes is influenced by phorophyte species, and many epiphytes are restricted to a certain zonation in the tree crown. The propagules of epiphytic plants are characteristically tiny, such as spores and dust seeds, and thus the first life stages in the crown will be small and difficult to observe, and the life span until maturation is often quite long. It is an often overlooked fact that the establishment site of an epiphyte is located in an environmental gradient that is moved by the growth of the phorophyte. The niche suitable for establishment is likely to be much more exposed than the environment in which the epiphyte eventually matures, and the bark younger. This environmental change easily explains the zonation in epiphyte distribution. Positions within the tree crown can be dated by means of growth rings, conveniently yielding a maximum age of epiphyte life stages. All phorophyte features, such as bark rugosity, pH, bark chemistry, microbial community and bark surface microclimate should ideally be recorded in relation to age/position gradient, and conditions at the establishment sites given special attention.  Without new such sites, an epiphyte species is not able to maintain its presence in the tree.
Key words: bark features; establishment site; symbiosis; zonation