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E.S. Fernando: Vegetation of the Philippine Islands 4
deciduous forest reported on Palawan Island (Hilleshog 1985). The western side of the
archipelago, including Palawan, has a seasonally dry climate characteristic of areas where this
formation occurs.
3. Forest over limestone
The limestone forest in the Philippines'is known as the "Molave" (Vitex pan/Mora) forest owing
to the distinct presence of this species. This formation occupies low limestone hills, either
coastal or bordering large uplifted river valleys, which are mainly composed of crystalline
limestone covered by a shallow or very thin soil.
This formation is generally open. Its large trees are few and scattered. The intervening space
are filled with small trees and growth of usually sprawling, climbing and small erect bamboos.
With a few exceptions, the dominant trees are short-boled, irregular in form and with wide-
spreading crowns. The forest has a deciduous foliage, especially on rough topography in
regions where the dry season is pronounced.
A number of leguminous trees are dominant in this formation, viz. Afzelia rhomboidea, Sindora
supa, lntsia bijuqa, Albizia acle, Wallaceodendron celebicurn, Pterocarpus indicus and
Kingiodendron alternifoliurn. Other dominant species include Pterocymbium tinctorium,
Zizyphus talanai, Toona calantas, Mimusops elengi, Maranthes corymbosa, Wriqhtia
pubescens, Lagerstroeniia pirifonnis, and Heritiera sylvatica, and such smaller trees as
Diospyros ferrea, Pterosperm um diversifolium and Mallotus floribundus.
4. Forest over ultramafic rocks
This formation occurs in soil rich in heavy metals and is generally characterized by a
sclerophyllous stunted vegetation with sharp boundaries. In the Pnilippines it is found on
Palawan (Hilleshog 1985), eastern Isabela, Luzon (and possibly also in northern Zarnbales),
northeastern Mindanao, and on Dinagat Island.
Some of the ultramafic forests on Palawan are only about 2-5 m tall and contain a unique flora
including, among others, Planchonella sp. and the heavy metal indicators Scaevola micrantha.
Brackenridgea palustris and Exocarpus latifolius (Hilleshog 1985). Other tree species include
Ochrosia glomerata and species of Gymnostoma, Suregada, Archidendron and Pouteria. The
Mt Victoria area is the largest region of ultramafic forests on Palawan and is home to the
endemic tree Embolanthera spicata, one of only two species in the genus (the other being in
Indo-China).
On Dinagat Island and also the northeastern tip of Mindanao and northern Leyte the ultramafic
forest contains the endemic tree Xanthostemon verdugonianus.
This formation in the Philippines needs further investigation particularly of its unique flora.