Vegetation of Southeast Asia Studies of Forest Types 1963-1965

Chinese; and the remaining 5 percent includes Malaysians, Cambodians,
Laotians and other groups. About 90 percent of the people live in
comaimities of less than 5>000 inhabitants.
The Thais are primarily engaged in agricultural pursuits, inhabiting
the thousands of small villages, concentrated mostly along
highways and the network of canals find rivers. Most of the positions
in the Government, police, and military organizations are held by
Thais, although the Chinese minority is active and influential in the
economic life of the country. It is estimated that about 50 percent
of the 3 1/2 million Chinese reside in the Bangkok-Chao Phraya area,
while the remainder are scattered throughout the country in commercial
centers, market towns, and large villages.
Physiographic Regions
In general there are three major physiographic types: highlands,
plains, and plateaus, which grade ipto one another and support mc.-e
or less distinct types of vegetation. The highlands comprise several
mountain ranges, in general extending from north to scuth .along the
entire western length of the country (Fig. 3)- The central region is
occupied ty a great alluvial plain of deltaic form with the base at
the Gulf of Thailand and its apex in the Uttaradit area. The northeastern
part of the country includes an extensive plateau, flanxeci
by Fountains along its western and southern borders.
Based on land forms, which also coincide with the classification
of cxLimate and vegetation types, Thailand may be divided into five
physiographic regions (Fig. 2): (l) the northwest highlands; (2) the
Chow Phraya or central plain; (3) the Korat plateau; (h) the Chantaburi
region; and (5) the Peninsular region.
As elsewhere in Southeast Asia, the climate of Thailand is controlled
by the seasonal monsoon modified by local topography. Two
broad types of climate prevail: that of the Rain forest and that of
the Monsoon forent or Savanna (Figs. ^,5). Optimal Rain forest climate
is characterized by uniformly high temperature and lieavy rainfall
distributed throughout the year with no distinctly dry season.
The Monsoon or savanna climate, en the other hand, has less prc--
cipitation and is divided into wet arid dry seasons.
Owing mainly to the modifying influence of topography, five
climatic zones are also recognized: northern Thailand, comprising
•che eight provinces from Uttaradit northward; the central plain,
corresponding +.0 the area south of Uttaradit to the head of the Gulf
of Thailand, and including the area north of Prachuap-Khirikhan, in
the upper Peninsula; northeast Thailand, which embraces the entire
Korat plateau; the southeast region along the Gulf of Thailand; and