Vegetation of Southeast Asia Studies of Forest Types 1963-1965

Topography: The general physiography, of Southeast Asia is that
of mountain ranges, with peaks upwards of 6, 5CX) feet (8, OCX) n.) in
altitude, deep gorges, plateaus and great plains. The entire region
is drained by numerous rivers, most of which flow in a southerly or
southeasterly direction, and their estuaries form extensive deltas.
Puerto Rico contains three physiographic regions: (a) a central
mountainous core of vdicanic origin; (b) an, elevated area of coral
limestone, formerly marginal marine deposits, surrounding the mountain
ranges; and (c) the northern and southern coastal plains. Few
countries of comparable size are so well-watered as Puerto Rico.
Within its mountainous area there are many swift-running streams,
flowing through deep gorges and s-oeep-sloped valleys. It is reported
that the island has about 1,300 small and large streams, of which
the Rio de la Plata, about 4 5 miles (72 kmsi) long, is considered the
largest. Except for small boats, these rivers are navigable only in
their tidal reaches.
On a broad basis, there are three major physiographic conditions
in Texas: (a) mountains and basine of the Trans -Pe cos; (b) fairly
level plains as exemplified by the lur;n plains and Gulf prairies;
and (c) rolling or irregular topography as typified by the rolling
plainn. South Texas plains, Hill country ov Edwards plateau, anc'.
East timberlands.
The principal mountains of TV^as are in the Trans-Pecos region
where the Rocky Mountain system crosses over from New Mexico to Old
Mexico. The highest point is Guaxielupe peak, 8,751 feet (2,650 m.).
The Baleones Escarpment provides a rather distinct dividing line betvcen
the eastern Kdwards plateau and the South Texas plains and
Rlack.1 and 3. Another prominent physiographic feature is the Cap Rock
Escarpment, separating the high and rolling plains. Ms ly streams
dissect the 3-uate, flowing irregularly from the northwest to the
Gulf Coast.
Climate: In Southeast Asia the climate is controlled by the
seasonal monsoon, modified by local topography. Two broad types of
climate prevail: that of the Rain forest and of Savanna. The optimal.
Rain forest climate is characterized by a uniformily high temperature
and rainfall distributed throughout the year, with no prolonged dry
season. The tropical Savanna climate, on the other hand, .has less
precipitation, varying up to 80 inches, with distinct rainy and dry
seasons of almost equal duration. This is modified regionally under
the influence of topography. • The prevailing winds in Thailand are
the southwest monsoon, which corresponds to the wet season, and the
northern or northeast monsoon, during the dry season.
Owing mainly to the modifying influence of topography, five types
o** climate are recognized In Thailand: (a) Northern region, with a
monsoon climate influenced considerably by local elevation, producing
a so-called mountain climate, with temperature extremes ranging from
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