Vegetation of Southeast Asia Studies of Forest Types 1963-1965

This forest type is rather widespread in Thailand, found in
such areas as around Pranburi, in the upper Peninsula; at Prachuab-
Khirikhan, in the central Peninsula; in the area of Mukdahan and elsewhere
in the northeast; Pokadien, in. the region of Loei, in the north; and
especially along banks of rivers or streams scattered throughout the
country.
Woody species occurring in this type of forest vary from one
region to another. For example, in the Pranburi area, a dominant
plant is Streblus zeylanicuro, constituting about 50 percent of the
vegetation. Other trees in this dry forest include species of Vitex,
Diospyros, Fieus, Eugenia., Aglaia, v/alsura, Hopea, Spondias, Salmalia,
and Cratoxylon.
Some of the trees and shrubs in the uuderstory are thorny* Woody
constituents are species of Hydnocarpus, Murraya, Atalantia, and
Taxotrophis. Rattans (Calamus) may also be present. Bamboos face represented
Uy Bambusa arundJnacea, Dendrocalamus strictus and species
of C-lgantochl "^a.
Semi-Evei-green forest; This subtype also has a wide distribution
in Thailand. The trees are of medium stature, ranging from ^'5 "to
60 ft. (15-20 m.), although some emergent species may attain 90 ft.
(30 m.). Usually they have straight trunks, with a diameter of 12 to
2k inches (30-60 cm.). The majority of the trees shed their leaves,
at some period of the year, but in general this subtype has a Semi-
Evergreen appearance.
Typical of a Semi-Evergreen forest is found around Tak, in the
northwest. Important constituents of this subtype in that area are:
Afzelia xylocarpa, Alangium salvifolium, Cassia garrettiana 'and £._
siaraea, Chukrasia velutina," Dal berg ia cultrata, Dillenia sp.,
Dipterocarpus tuberculatus, Eryxhrophloeum teysmsjinii, Garuga pinnata,
Hopea odorata, Lagerstroemia I'lo.i-regina, Michelia champaca, Pterpcarpus
macrocarpus, Terminalia tom'antosa and Vitex putescens.
MONTANE FOREST
Changes in vegetation, corresponding to increasing altitudes, are
just as striking in the moist tropics as they are in temperate regions.
As we ascent a forest-clad mountain slope, such as in northern Thailend
for example, there is a decided change in the fioristic composition
and structure of the vegetation. .The luxuriant Rain and
Moist Evergreen forests are gradually replaced by trees of entirely
different, species olio, even genera, and generally of smaller dimensions.
The Montane forest commences at an altitude of approximately
3,000 ft. (1,000 ra.) and extends to the cre^t of high mountains to
at about 8,000 ft. (2,^00 ra.). In-between the Upper Moist Evergreen
forest and the Montane forest there is usually a transitional belt of
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