Travellers in the tropics know very well the phenomenon shown below:
That picture is of bromeliads growing naturally on power lines here in Jalpan. The bromeliad is TILLANDSIA RECURVATA, sometimes called Small Ballmoss, though its a bromeliad, not a moss. As you might expect with a species that can grow on power lines, this is a tough little plant with an enormous distribution throughout tropical and part of subtropical America. It's found from as far north as Georgia and Arizona south to southern South America. Ive even seen it growing on cactus spines and barbed-wire fences.
Seeing Tillandsia recurvata on power lines should dispel any suspicions you might have that epiphytes -- plants growing on other plants and elevated structures -- have to be at least a little parasitic on their hosts to survive.
The vast majority of epiphytes aren't parasitic at all. They just grow epiphytically because they need a place to live and their perches give them access to light. Though the percentage is much less in temperate climates, when the whole world's seed plants and ferns are considered, about 10% of them are epiphytes. Over half of the Orchid Family's 20,000 species are epiphytic.
Whenever you read how epiphytes manage to survive you find a great deal about dust, trapped organic debris accumulating around plant bases, and trickling rainwater, but there's little said about microorganisms. Recently studies have shown that in many epiphytic species bacteria play a huge role by fixing atmospheric nitrogen. Almost all orchids have mycorrhiza associated with their roots which provide the plants with micronutrients. Our little Tillandsia recurvata has been shown to have its blade surfaces populated by the nitrogen-fixing bacterium called Pseudomonas stutzeri.
So here's more evidence that we underestimate the importance of microorganisms in our lives, and to Life on Earth. We've already spoken of how very much the health and survival of animal species -- humans being animals -- depend on a diverse, well balanced population of bacteria being present in our guts.
Sometimes I think that future generations may regard the manner in which we abuse the planet's microorganisms as even more disastrous than how we deal with global warming and nuclear proliferation. When we clear-cut a forest and cause so much erosion and oxidation of the soil's organic content, that's devastating on the established bacteria. From the regenerating forest's point of view, loss of a healthy community of bacteria may be worse than losing normal soil structure and the forest's self-regulating microclimate.