Paleovegetational reconstruction from fossil opal phytolith assemblages in the soil of tropical seasonal forests in Thailand

To reconstruct the distribution changes of tropical seasonal forests in the several regions in Thailand, from early Holocene to recently, analyses of fossil opal phytolith were carried out together with radiocarbon dating. Three paleovegetation types were identified from the composition of Shorea type and Bambusoideae phytolith assemblages and radiocarbon dates. A-type is distin-guished by a standing of temperate deciduous dipterocarp forest on the flatland less than 100 m above sea level of the northern Malay Peninsula (after ca. 9,300 yrs BP). B-type is defined by increasing of temperate deciduous dipterocarp forest with Bambusoideae in the forest floor on inner hills, northeast Thailand (after ca. 5,000-4,500 yrs BP). C-type is characterized by vegeta-tional flora in mountainous areas more than 500 m above sea level in northern Thailand (after ca. 1,000 yrs BP). It was revealed that deciduous dipterocarp forest expanded from low latitudes to high, and from low land to highlands. It was suggested that paleovegetation was induced not only by environmental change, but also by human impact on ecosystems.