Click to read the timbers details
in full 10 pages.

Click to see the common names, the scientific name of the northern forest trees.

Created:09/2/1998  

Maintained page by
  Sanguan Chantalay 

 Last updated:
September 14, 2008

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The Forests of Northern Thailand  in the decades of 1960 condensed and abrogated from reports for  educational and research purposes. USDA/ARS Report CR 12-67. Issued: September 1967

In northern Thailand the Dry and Moist Deciduous forests, where teak abounds, have been studied ecologically and taxonomically during the past 50 years or so by British botanists, Craib and Kerr, and  in recent years by botanists and foresters of the Royal Forest Department, Kasetsart University, and other scientific institutions, including, American, Danish and Japanese investigators.  But extensive areas still remain to be surveyed, particularly the Evergreen Rain forest in the southern Peninsular, covering the eastern mountain ranges along the Cambodian border, in the Khao Yai National Forest in the central section bordering the Korat plateau, or the various types of forests in the extreme northeastern and northwestern sections of Thailand. 

(p. 2; USDA/ARS, LLewelyn Williams, CR 12-67, September 1967) 

Thailand:  Under monsoon conditions, four fairly well-defined seasons may be recognized in Thailand, and likewise in the adjacent Mekhong basin countries: (a) Northeast monsoon from December to February, with little rain, which corresponds to the cool or  dry season; (b) the warm season, also almost rainless, with highly variable winds and transitional hot weather, during March to May; (c) the rainy season, from May to October, when the rains cool the atmosphere and the temperature is generally lower; and (d) the retreating monsoon period of October and November. 

In most areas of Thailand the mean monthly temperature ranges from mid 70'sF. during the coolest months (December and January), to mid 80'sF. for the warmest Spring months (April or May).  With the advent of the Northeast monsoon in November, when the dry season normally begins, Thailand enjoys cool nights, and temperatures as low as 40"F. may prevail in some of the northern upland areas.  During the hot months of February and March, daytime temperatures in Bangkok are almost always in the 90"'s, and often reach 100"F. in the interior. 

With the exception of the Peninsula, in most parts of Thailand almost 90 percent of the annual precipitation of 40 to 80 in. (1,000 - 2,000 mm.) falls during the southwest monsoon, from May to October.  At that time the relative humidity seldom falls below 70 percent.  In the central plain of Thailand the average annual rainfall decreases progressively from south to north.  For example, Bangkok has an average of 59 in. (1,475 mm.); Lophuri, 54 in. (1,250 mm.); and Nakhon Sawan, in the upper part of the central plain, has 43 in. (1,075 mm.).  The driest regions are in the rain shadow of escarpments between the central plain and the Korat or northeastern plateau; and along the eastern base of the Tenasserim range, on the west, from the upper Peninsula northward to Kanchanaburi and Tak.  The influence of the rain shadow on the vegetation in that area is shown by the frequency of dry bamboo brakes, intermixed with thorn brush. 
p. 12 

Shifting agriculture, the simple, primitive "ray" system, accompanied by periodical burning has been practiced for centuries in Southeast Asia as in other tropical regions.  A small plot is selected in the forest to grow food crops.  After two or three seasons the soil becomes impoverished.  The site is then abandoned and soon becomes covered with Imperata and other grasses, shrubs, and fast-growing, soft-wood trees of small stature, or entirely different species from the original growth. p.17-18 

In Thailand Dipterocarp forests cover about 45 percent of the country's total forested area and have long been an important source of useful timbers both for domestic use and for export.  They are especially well represented throughout the continental part of Thailand, particularly in the east and northeast, forming almost pure stands of mixed with other Hardwoods, and some genera constitute a characteristic element of wooded savannas.  Several species of Dipterocarps are also represented in the Rain of Moist Evergreen forest.  They are of extremely variable dimensions, from dwarf trees, such as Shorea obtusa in savannas, to the tall, corpulent, ubiquitous "young" (Dipterocarpus alatus).  p.21 

Of the total area of Thailand, approximately 120,000 square miles are covered by some type of forest.  Of these, 36,000 square miles are evergreen forests, including Mangrove woodland and stands of pines.  Humid forests form the bulk of these, while pine forests represent less than 5 percent of the total forested area.  Of the remaining 84,000 square miles, about 30,000 square miles are covered by Mixed Deciduous forest, concentrated mostly in the north and northwest, and Dipterocarp forests (about 45,000 square miles) form extensive open stands, especially in the east and northeast. p.22 

Several species of oak (Quercus), usually mixed with other Hardwoods, and at higher elevations with Conifers, are frequent at medium altitudes in the Montane forest of central and northern Thailand, as well as in Vietnam, Laos and Cambodia. p.23 

At higher elevation, in Mid-mountain forest of Khao Yai, central Thailand, the most frequent forest trees are species of oaks (Quercus), chestnut (Castanopsis), and a conifer, Podocarpus.  These do not appear in the surrounding Hill Evergreen forest at lower elevation. On the flat summit other trees become dominant, such as species of Schima and a conifer, Dacrydium.  Unlike the Rain forest, Montane forest has two, not well marked stories, and most of the trees are slender, with fairly small crowns, and form rather close stands.  On the mountains of northern Thailand the oak-chestnut  association is gradually supplanted by stands of the 3-needled pine (Pinus khasya). p.26 

Montane Forest: 
In northern Thailand, in the region of Chiengmai, the upper limit of the Dipterocarp forest may be taken as the approximate dividing line between the Lowland forest and the Mountain forest.  For example, the lower east sloper of Doi Suthep, which has an altitude of 5,450 ft. (1,676 m.), is covered by Dry Dipterocarp forest up to about 2,300 ft. (700m.).  Between 2,300 and 3,200 ft. (700 - 1,000m.), the vegetation is an intricate mosaic of Dry Dipterocarp and Mixed Deciduous forests, intermixed with evergreen trees of the Montane formation, with species of oak (Quercus) and chestnut (Castanopsis) as dominants.  Oak trees attain a height of 50 to 65 ft. (16 - 20 m.), and a diameter of about 12 in. (30 cm.).  A thin layer of humus and thick litter accumulate on the forest floor.  The ground layer is composed mainly of lalang grass (Imperata cylindrica). p.101 

Coniferous Forests: 
In Thailand,  Conifers form less than 1 per cent of the total forested area of the country.  The most frequent genus is pine, of which there are two species - the 3-needled Pinus khasya, with furrowed bark, at higher altitudes; and the 2-needled P. merkusii, with scaly bark, somewhat at lower  elevation. 
In Thailand, the most extensive pine forests occur in the north, particularly in the upland region around Chiengmai. West of this city, they are found at altitudes from 2,000 to 5,200 ft. (600 - 1,620 m. ) on the upper ridges of the mountains Sutep, Puy and Inthanon; also on the summit of Chiengdao range, and northward toward the border of Burma.  On the plateau of Bo Luang, southwest of Anka range, also in northern Thailand, there is an extensive pure stand of the 3-needled Pinus khasya, at an elevation of 3,000 to 4,000 ft. (910 - 1,200 m.), surrounded by Moist Deciduous forest.  To the northwest, towards the border of Burma, pines form rather large stands between Chiegmai, Mae Hongson and Mae Sariang.  In the northeast of Thailand, pines are dominant in the Pokadien mountains, on the plateau of Loei.  The trees are rather widely spaced, so that the pine forest is usually open, and visibility, both horizontal and vertical, is favorable. The ground cover is composed of grasses, especially Imperata, and ferns. 

The 2-needled Pinus merkusii found as low as 1,300 ft. (400 m.) in the province of Phetchanbun, at the northern end of the central plain. It occurs at still lower altitudes in the region of Phibun Mangsahan, in eastern Thailand, where it may be mixed with Dipterocarp forest.  p.108 

Timbers and Other Forest Products of Thailand

The forests of Thailand contain a wealth of timber trees and other forests products, which represent an important source of revenuer for the country.  Principal of these timbers, of course, is teak (Tectona grandis), concentrated mainly in the northern Mixed Hardwood forests.  For many decades Teak figured as the principal timber used within the country and for export.  In recent years, however, exports of other timbers, particularly those of the Dipterocarp family, have equaled those of Teak.  Because of over-cutting in former years, and destruction caused by shifting agriculture and fire, there is a need for a systematic program to restore the teak forests as well as some of the other more important commercial trees. --p.228   

We wish to see the green year in 2000. Join together to plant a tree in 
your home yard. 

Sanguan Chantalay 
Pangfan Nature Farm 
Chiang Mai, Thailand 
September 2, 1998