DEVELOPMENT AND DISTRIBUTION OF THE EPIPHYTIC FLORA IN AN AMAZONIAN SAVANNA IN BRAZIL

The abundance and distribution of epiphytes were studied in a plot of about one third hectare of Amazonian savanna close to the city of Huma ita (7-degrees-31'S, 63-degrees-00'W; altitude almost-equal-to 50 m). Non-vascular epiphytes (lichens and bryophytes), apparently undergo su ccession on trunks and branches of their host trees. While lichens dom inate in young trees, and usually diminish in quantity on older ones, bryophytes are more abundant on older trees and seem to surpress the l ichens. In total, 118 juvenile and adult individuals of 7 vascular epi phyte species (Catasetum saccatum: 65 individs., Polypodium decumanum: 33 individs., P. hirsutissimum: 16 individs., Polystachya estrellensi s, Polypodiaceae sp., Gesneriaceae sp. and Araceae sp.: 1 individ. eac h) were found on 18 of the 111 tree individuals of the plot. The furro wed and persistent bark of Physocalymma scaberrimum-trees seems to off er by far the best conditions for settlement and growth (average 2 epi phytes per tree). On the other hand, the flaky deciduous bark of Curat ella americana and the smooth one of Cordia bicolor (averages about 0. 2 epiphytes per tree) apparently make settlement more difficult. As mu ch as 113 epiphytes (almost 96 %) were found on 15 trees higher than 4 .5 m, whereas only 5 (about 4 %) had settled on 3 lower ones. Further, there appears to exist a positive correlation between density of vege tation and number of epiphyte individuals. Since the humid Amazonian c limate permits vascular epiphytes to grow even in strongly insolated o pen savannas, the factors which determine their development seem to be the specific surface characteristics (mainly bark) of the host trees, the age of the trees, and also the density of vegetation. However, be cause of the low number of epiphyte bearing trees within the investiga ted plot, none of these three chracters is statistically significant.