MEHLTRETER, KLAUS*, JOSé G. GARCíA-FRANCO, AND ALEJANDRO FLORES-PALACIOS. Instituto de Ecología, A.C., Departamento Ecología Vegetal, Apartado Postal 63, Xalapa 91000, Veracruz, México. - Microhabitat preferences of trunk epiphytes in a cloud forest of Mexico, with special reference to ferns.
Aim of this study was to investigate microhabitat preferences of
epiphytes in relation to trophophytes and to exposition and location
on the trunk. The study site is a cloud forest fragment, located in a
river gorge in central Veracruz (19°30'N, 96°59'W) at 1550 m altitude.
There, annual precipitation is 1440 mm and the average temperature is
18.0°C. Trees were marked at the end of the rainy season along four
transects of 30 m length, running perpendicular to the river. All 100
trees within 2.50 m distance of the transect were checked for trunk
epiphytes between 0-1.50 m height. Frequency and cover for each
epiphyte species were estimated with a modified scale of
Braun-Blanquet, for three ranks of 50 cm height and for the river and
mountain exposed side. Most abundant tree species were the angiosperms
Arachnothryx capitellata (Rubiaceae), Clethra mexicana
(Cyrillaceae) and Liquidambar styraciflua (Hamamelidaceae), and
the tree ferns Alsophila firma and Cyathea divergens
(both Cyatheaceae), the latter two with highest cover rates of
epiphytes. Most abundant epiphyte species were Trichomanes
capillaceum, Trichomanes reptans (Hymenophyllaceae) and
Peperomia quadrifolia (Peperomiaceae). Strongest microhabitat
preferences were found between Trichomanes capillaceum and both
tree fern species, while Peltapteris peltata was exclusively
present on angiosperm trees. Also Trichomanes reptans occurred
mostly on different angiosperm trees, and finally Peperomia
quadrifolia was indifferent in relation to trophophytes. Some
epiphyte genera showed preferences for only one of the tree fern
species: Asplenium (Aspleniaceae) and Elaphoglossum
(Lomariopsidaceae) were significantly more frequent on Alsophila
firma, while Syngonium (Araceae) was more represented on
Cyathea divergens. Species diversity of epiphytes was higher on
the river exposed side and increased from the lower to the higher
trunk sites, while the species coverage decreased.
Key words: cloud forest, ecology, epiphytes, ferns, Peltapteris peltata, Trichomanes capillaceum