บทคัดย่อ :
Thailand is situated in the Southeast Asian region, covering the latitudes between 5 and 20(degrees) N and longitudes between 97 and 106(degrees) E with a total land area of 515 113 km2, or about 51 million hectares. The total forest area, which included natural forest of 164 865.40 km2, reforestation area of 3551.40km2 and secondary growth of 3633.30 km2 is 172050.00 km2 or approximately 33.4% of the country s total area (RFD 2001). The range of elevation is from sea level up to 2200 m. Climatic conditions vary from the lowland humid tropics to alpine and subtropical types. Annual rainfall varies from below 1000mm in the north and the northeast to above 2500mm in the south. Thailand is topographically divided into five regions: the north, northeast, central, east and south. The northern region, which is hilly and mountainous, lies on the fringe of the Himalayan foothills. Those mountains give way to the plain of northeastern region of the country. The Chao Phraya River and its four main tributaries formed the alluvial floodplain of the central region. The natural vegetation is extremely diverse. It is one of the richest countries of the world in biological resources. This is attributed to its biogeographical location, which is at the junction of the three main floristic regions, namely the Indo-Burmese, the Indo-Chinese and the Malesian regions (Smitinand 1994, cited by Boontawee et al. 1994) The Indo-Burmese floristic region prevails in the northern, northwestern and western parts of the country. The Indo-Chinese floristic region is found in the northeast, whereas the Malesian floristic type is found in the southern peninsular and in the eastern parts of the country. Therefore, the natural forest vegetation of Thailand ranges from upland pine forests on the border with Lao PDR and Myanmar in the north to lowland rain forests in the far south. It is estimated that more than 10000 plant species made up natural vegetation of the Kingdom (RFD 1996). The majority of forest lands in Thailand are the asset of the state. At present the government agencies responsible for forests are the Royal Forest Department (RFD) and the National Park, Wildlife and Plant Conservation Department (DNP). Since the founding of the Royal Forest Department in A.D. 1896 timber exploitation from natural forests, especially teak (Tectona grandis L.), was done through selection with minimum girth system silvicultural practice. Teak tree with girth at breast height higher than 212cm was allowed to harvest. The same system was also used with non-teak trees but with different minimum girth limits according to tree species (RFD 1996). The silvicultural practices used in the past did not cause severe depletion to the forests. However, the country s forests have been subject to clearance and degradation for many years, though the current situation is more stable. Forests covered over half of Thailand s land area in 1961 but, by 2001, they had been reduced to just over 33.40% (RFD 2001). Demand for land for various uses, including subsistence farming and commercial agriculture, has been the main cause of deforestation. Rapid population growth has also elevated the demand for wood products and the consequent exploitation pressure on forests. Deforestation has had a severe impact on Thailand s environment and economy. Between 1981 and 1991 the rate of destruction was about 515 000ha per year.
เอกสารอ้างอิง :
Sumantakul, V. (2004). Status of forest genetic resources conservation and management in Thailand. In Proceedings of the Asia Pacific forest genetic resources Programme (APFORGEN) Inception Workshop, Kepong, Malaysia, 15-18 July, 2003 (pp. 265-289). IPGRI-APO Serdang, Malaysia.
