In tropical rain forest, the interface between leaf surfaces and the atmosphere is a fundamental pathway for nutrient cycling (particulary nitrogen), possibly even more important than the soil–plant interface (Parker 1994, Silver et al. 1996). Most important nutrient exchanges in the phyllosphere–atmosphere interface are mediated by microbial populations. For example, some authors have considered that nitrogen fixation in the phyllosphere is the main mechanism for nitrogen gain in humid tropical ecosystems, because of the substantial nutrient demand resulting from a high plant productivity and the constraint imposed by the generally low nitrogen availability in soil (Ruinen 1974, Salati et al. 1982, Silver et al. 1996).