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 Limestone Forest

These forests are confined to limestone, but are sometimes referred to as molave forest due to the conspicuous presence of this species (Vitex parviflora). They also contain large numbers of leguminous species and many of the trees are deciduous. Among other characteristic trees are Afzelia rhomboides, Heritiera sylvatica, Intsia bijuga, Kingiodendron alternifolium, Lagerstroemia piriformis, Mimusops parviflora, Parinari corymbosa, Pterocarpus indicus, Pterocymbium tinctorium, Toona calanthes, Wrightia pubescens, Ziziphus talanai, endemic taxa like Litchi chinensis subsp. philippinensis (Sapindaceae), Sindora supa (Fabaceae) and the near endemic Wallaceodendron celebica (Fabaceae). Not surprisingly the latter species also occurs in the forests of Sulawesi (Celebes). Other characteristic but less common endemic species include Heterogonium lobulatum (Dryopteridaceae), the epiphyte Microsorum samarense (Polypodiaceae), Pneumatopteris lithophila (Thelypteridaceae), Sphaerostephanos subcordata (Thelypteridaceae) and various species of Tectaria such as T. athyriosora, T. calcarea and T. tabonensis (Dryopteridaceae).

Philippinean Ultrabasic Forest

There are substantial areas of ultrabasic rock in the Philippines. Examples include Mount Bloomfield on Palawan and Mount Giting-Giting on Sibuyan. The forests are typically stunted although the reason for this is not absolutely clear. It could be due to a shortage of essential nutrients or to the high levels of magnesium and calcium or high nickel concentrations. On Mt Bloomfield the forest trees mainly comprise various metaliferous species such as Brackenridgea palustris var. foxworthyi, Exocarpus latifolius and Scaevola micrantha, while other trees include Gymnostoma mesostrobilus and Phyllanthus balgooyi. Several species, such as the endemic shrub Walsura monophylla (Meliaceae) are known to be nickel hyperaccumuators. The value of this adaptation is unclear but possibly renders their leaves toxic to certain herbivores. Other endemic species associated with these untrabasic rock forests include trees such as Myristica colinridsdalei (Myristicaceae) and shrubs such as Licania palawanensis (Chrysobalanaceae) and Securidaca atro-violacea (Polygalaceae). 

References

Brown, W. H. 1919. Vegetation of Philippine Mountains. Publication No. 13. Department of Agriculture and Natural Resources, Bureau of Science, Manila.

Hamann, A., Barbon, E. B., Curio, E. & Madulid, D. A. 1999. A botanical inventory of a submontane tropical rainforest on Negros Island, Philippines. Biodiversity and Conservation, 8: 1017-1031.

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.

Pipoly, J. J. & Madulid, D. A. 1998. Composition, structure and species richness of a submontane moist forest on Mt Kinasalapi, Mindanao, Philippines. In: Forest Biodiversity Research, Monitoring and Modeling. Eds. F. Dallmeier and J. A. Comiskey. Man and the Biosphere Series, Volume 40. The Parthenon Publishing Group.

Proctor, J. 2003. Vegetation and soil and plant chemistry on ultramafic rocks in the tropical Far East. Perspective in Plant Ecology, Evolution and Systematics, 6: 105-124.

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.