Flora of Thailand
Thailand is one of the tropical countries teeming with diverse flora and vegetation. The diverse vascular plants of Thailand with estimated number of no less than 10,000 species, have been recorded and published in continuation in the Flora of Thailand since 1970. The physical features of Thailand range from the sea level to 2565 m (Doi Inthanon) elevation, and from high mountains along the Tenasserim Range in the north to flat top sandstone mountains in the northeast, through the flat alluvial plains in the central, the eastern adjacent to Cambodia, and in the peninsula to the Malaysian border. Most of the mountains are situated in the north including the three highest peaks: Doi Inthanon (2565 m), Doi Pha Hompok (2285 m), and Doi Chiang Dao (2175 m), and several peaks about 2,000 m elevation. The highest montanins in southeastern region is Khao Soi Dao (1675 m) in Chanthaburi, and in the peninsula is Khao Luang (1835 m) in Nakhon Si Thammarat. The country has a monsoon climate with a markedly dry season of 3-5 months, except in the southeast in Trat provincial areas and the peninsula where rains are more or less prevailing throughout the year. Most parts of the country have three seasons, i.e. rainy, cool and dry except for the southeast and peninsula which have only two seasons, i.e. rainy and dry. Temperatures are varied with the seasons and elevations. More generally, humid sub-tropical and tropical climates are applicable to most parts of the country.
At present, the natural forest cover is an estimated 25 % of the total land area. Vast forest areas have been converted into secondary vegetation mainly by the urban developments and the expansion of agricultural lands. Nevertheless, the vegetation of Thailand is varied and can be classified into evergreen and deciduous forest types which are basically based on varying moisture gradients, temperatures and altitudes. The names of the dominant tree species are often used for associations and sub-types of vegetation, more technically, the characteristics of floristic composition is based, such as tropical evergreen rain forest, seasonal evergreen forest (or dry evergreen forest), montane forest, mangrove forest, peat swamp forest, strand vegetation, mixed deciduous forest and deciduous dipterocarp forest. In the north, type forests are ranging from mixed deciduous, deciduous dipterocap to seasonal evergreen forests below approximate 1,000 m, and montane forest above approximate 1,000 m. The mountains in northeastern region is characterized by plateau-top, the vegetation is mainly covered by deciduous dipterocarp forest. In central part, the region is mostly under agricultural cultivation. The southeast and peninsular regions are mostly covered by evergreen forests. Other vegetation types, pine forests are scattered throughout the country except in the peninsula, moreover mangrove and strand vegetations are restricted to the southeastern and peninsular coasts, whereas peat swamp forest is represented in an extensive patch in Narathiwat province near Malaysian border.
Botanically, Thailand is included in the Indochinese subdivision of the continental Southeast Asia, and phytogeographically, is situated between two floristic regions, viz. Malesian and Indochinese including Myanmar and South China. Thailand is considered as a collective centre of botanic diversity designated by three floristic regions: Indo-Burmese, Indo-Chinese, and Malesian. As a result, Thailand shares its flora with the neighbouring countries. The number of endemic species is, therefore, not high. However, the richness of flora of Thailand comprising of estimated 10,000 vascular plant species, represented by 275 families of spermatophytes and 36 families of pteridophytes. In deciduous forests, plant diversity is rather poor. The main canopy trees of both mixed deciduos and deciduous dipterocarp forests are dominant by the dipterocarp and leguminous tree species.
During the past decades, the much increased population in Thailand combining with economic and infrastructure development has been responsible for forest retreats in every region of the country. Since the establishment of the Royal Forest Department in 1896 and the inauguration of the Department of National Parks, Wildlife and Plant Conservation in 2002, both departments are authorized as the main agencies for the forest and wildlife conservation and sustainable management of the forest resources. At present, there are 147 national parks, 108 forest parks, 57 wildlife sanctuaries, 49 non-hunting areas, 16 botanical gardens and 55 arboreta throughout the country covering over 60 % of the remaining forest areas and containing most of natural resources of ecological importance in the country.