The relative importance of height as a variable influencing epiphyte communities varies with forest stature. Taller forests obviously have a much stronger vertical component of moisture gradients than shorter forests. Thus, vertical stratification of epiphyte communities is distinct in tall forests (e.g., McCune et al. 2000), while substrate effects and horizontal gradients of moisture availability are more easily distinguished in short forests (e.g., Kantvilas and Minchin 1989).
Epiphytic lichens and bryophytes are also affected by moisture gradients in tropical forest canopies. The horizontal component of the gradient tends to be pronounced in tropical trees due to their broadly domed crowns. In montane rainforests, bryophytes, especially liverworts, dominate inner and middle crowns (Gradstein et al. 2000)
In tall lowland rainforests, bryophytes are most abundant in inner and middle crowns as well as tree bases (Cornelissen and ter Steege 1989; Montfoort and Ek 1990).