Included here is the Philippine Achipelago and the Calamian Islands, Basilan Island, the northernmost island in the Sulu Achipelago, the Babuyan Islands and the Batan Islands.

Philippinean Dipterocarp Forests

These forests found throughout much of the Philippine Archipelago are dominated by members of the Dipterocarpaceae. Prior to human interventions they represented about 75% of the virgin forest area and contained about 95% of the archipelago’s standing timber. The dominant dipterocarps are Parashorea malaanonan, Pentacme contorta and Shorea guisa and these together with trees such as the endemic Canarium luzonicum (Burseraceae) and Celtis philippensis (Ulmaceae) form a closed canopy. The tallest of these trees, Parashorea malaanonan, can reach heights of 40 m. Two sub-canopy layers can usually be distinguised. In the middle layer, at about 20 m high, Diospyros ahernii, Diplodiscus paniculatus and the endemic Dillenia philippinensis (Dilleniaceae) and Strombosia philippinensis (Olacaceae) represent some of the more prominent trees, but this layer probably contains a greater number of species than the other two stories combined. The third storey reaches about 10 m. Here the main species include Laportea subclausa, Thea montana and the endemic Leea manillensis (Leeaceae). Other endemic trees include Dillenia reifferscheidia (Dilleniaceae), Dipterocarpus philippinensis, Hopea acuminata, Shorea astlosa, Vatica pachyphylla (Dipterocarpaceae), Eugenia luzonensis (Myrtaceae), Gloeocarpus patentivalis (Sapindaceae), Guioa discolor (Sapindaceae), Hydnocarpus cauliflora (Flacourtiaceae), Leea philippinensis (Leeaceae), Mastixia tetrapetala (Mastixiaceae), Myristica rubrinervis (Myristicaceae), Pandanus luzonensis (Pandanaceae), Symplocos verticillifolia (Symplocaceae) and Terminalia pellucida (Combretaceae).

At ground level rattans (Calamus and Daemonorops) in their rosette stage are one of the most prominent elements. Other shrubs comprise various endemic species like Anaxogorea luzonensis (Annonaceae) and Osmoxylon oblongifolium (Araliaceae). In these more shrubby areas, herbaceous species are scarce, but in the wetter areas, particularly in ravines, they become much more conspicuous. Species of the shallow rooting genus Elatostema can be present in large numbers, while endemic species may include Carex nodiflora (Cyperaceae), Plectranthus merrillii (Lamiaceae), Sedum ambliflorum (Crassulaceae), Tectaridium macleanii (familiy), and by rivers the generic endemic fern Podosorus angustatus (Polypodiaceae). Ferns can be present in large numbers but most are fairly small species, while the spectacular Angiopteria angustifolia has fronds up to 5 m in length. Some of the more bizare ground dwelling species include the showy endemic parasite Rafflesia manillana (Rafflesiaceae) and the endemic leafless orchid Taeniophyllum philippinensis (Orchidaceae). With its photosynthetic roots this latter species is also occasionally found on the trunks of trees. However, epiphytic vegetation in general is quite scare and mostly confined to the large branches of tall trees where they often form a veritable aerial garden. Ferns such as Asplenium nidus (bird’s-nest fern) and various endemic members of the Polypodiaceae like Drynaria descensa, Microsorum heterolobum, Platycerium grande and Pyrrosia samarensis are common, while the flowering plants are mainly orchids or species of Hoya. Phalaenopsis amabilis is a spectacular orchid of these high branches but is rarely seen. Climbers, on the other hand, are very common. The most noticeable of these are the climbing palms (rattans). These start of as self-supporting ground species with spiny, pinnate leaves of up to 3 m until they send out climbing stems which can reach lengths of more than 100 m. Other conspicuous climbers are the climbing bamboos such as Schizostachyum diffusum (Poaceae) and other monocots of the genera Freycinetia (Panadanaceae) and Pothos (Araceae). Frequent among the dicot climbers is the endemic Symphorema luzonicum (Verbenaceae), but several others endemic dicot species of climbers and lianas may be encountered including Aristolochia leytensis (Aristolochiaceae), Cannarus whitfordii (Connaraceae), Cyclea cauliflora (Menispermaceae), Erycibe terminaliflora (Convolvulaceae), Prenacantha repanda (Icacinaceae) and Strychnos lanata (Loganiaceae).

References

Campbell, D. G. & Hammond, H. D. 1989. Floristic Inventory of Tropical Countries. The New York Botanical Garden.

Langenberger, G., Martin, K. & Sauerborn, J. 2006. Vascular plant species inventory of a Philippine lowland rain forest and its conservation status. Biodiversity and Conservation, 15: 1271-1301.

Leith, H. & Werger, M. J. A. 1989. Ecosystems of the World 14B - Tropical Rain Forests. Elsevier Scientific Publishing Company.

Steenis, C. G. G. J. van. 1957. Outline of the vegetation types in Indonesia and some adjacent regions. Proceedings of the Pacific Scientific Congress, 8: 61-97.