Altitudinal Zonation of Dicots on Mt. Pangasugan, Leyte Island, Philippines

Beatriz S Belonias, Norma O Aguilar
Vol 7 No 2 (2004), pp. 47-66




This paper presents an inventory of the dicot species and their altitudinal zonation on Mt. Pangasugan. It is aimed at augmenting our present knowledge of the vegetation of Philippine mountains, and to provide baseline information in the formulation of conservation and management strategies such as identification of priority sites for conservation. Four altitudinal vegetation zones were identified based on cluster analysis of 314 dicot species in 212 genera and 75 families. Zone I was the most luxuriant with well-developed tree, shrub and herb layers. Zone II was a high forest dominated by tall and large dipterocarp trees with a generally impoverished ground flora. Zone III has fewer and slightly shorter trees but with an increasing number of epiphytes. Zone IV, the summit zone, is a mossy forest having short, crooked trees laden with bryophytes and other epiphytes. Zone I (Sterculia-Voacanga-Acalypha-Elatostema association) occupied the lowermost forest belt covering 90-300 m asl. and is home to 43 families and 137 species of dicots. Thirty-two species e.g. Sterculia rubiginosa­, Voacanga globosa, etc were preferential to this zone. Zone II (Discocalyx-Psychotria-Phyllanthus-Canarium association), occurred at 300-600 m asl, and harbors 59 families and 159 dicot species. Hopea malibato, Anisoptera thurifera and Canarium asperum were some of the preferential species. Zone III, the Greeniopsis-Acmena-Calophyllum-Elaeocarpus association occurring at 600-900 m asl supports 37 families and 66 species of dicots. Zone IV, the Syzigium-Astronia-Hedyotis-Argostemma association is a mossy forest at 1000 m up to the peak of 1,158 m asl, with 22 families and 32 species. Astronia candolleana, Syzigium sp., Vaccinium myrtoides, Hedyotis elmeri, Drimys piperita etc. characterized this zone. Zone I and II, as well as Zone II and III, were more floristically similar while the most distant were Zone I and IV as well as II and IV. Species diversity decrease with altitude, Zone I being the most diverse and Zone IV, the least.


Keywords: floristic composition, altitudinal zonation, mountain flora, dicot, species diversity

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