Some new research by Cabral, Petter and Zotz, titled: What can fallen branches and vascular epiphytes reveal about the dynamics of epiphyte communities? looked at the influence of branch fall on epiphyte distribution in forests of Brazil and Panama.
They found that most epiphytes reach the ground after falling off branches rather than with branches. They attributed these falls to shedding bark and noted that large branches do not often fall - around 90% of fallen branches were less than 2 cm in diameter.
This likely means that the epiphyte populations of large branches are more limited by bark shedding than branch fall while those on the small branches of the outer canopy are the opposite, their distribution is limited by branch fall rather than bark shedding.
Bark shedding is important for epiphyte distribution in New Zealand forests. Trees like kauri and rimu are thought to rid themselves of pesky epiphytes and vines by dropping large bark flakes. The branch-shedding behaviour of kauri trees is also likely to minimise epiphyte loads. When investigating epiphytes on kauri, Sarah Wyse found that small epiphyte and vine species growing on kauri trunks between 0.5 and 3 metres from the ground are surprisingly abundant. This may be because they spread over multiple bark flakes and are too low down to be affected by dropped branches.
Next time you find a fallen epiphyte - have a look to see if it has been shed with a bark flake, dropped with a branch, or knocked off by something else...