Vegetational dynamics of Tertiary Himalaya

Abstract

Selected palaeobotanical and palynological records published from the Tertiary Period of Himalaya have been examined and a generalized vegetational frame work has been reconstructed. The diverse Palaeogene floras of Himalaya are marked by moist deciduous and wet semi-evergreen forest types growing mostly under tropical climate in varying type of environments. The tropical families register a decline in the Early Miocene time. The Middle Miocene Himalayan orogeny coincides with proliferation of Abietineae and by the appearance of several subtropical floral elements. Development and diversity of forest types are controlled by the altitudinal belts. The Pliocene floral diversification is related to climatic changes and increased continentality. The wet tropical forests disappeared from the low altitudes, whereas wet subtropical and temperate forests were transformed into dry or moist vegetational types. The appearance of semi-arid and cold conditions forced several moisture-loving plants, either to migrate or perish. The modern composition of the Himalayan flora reveals that it is a partial continuum of Neogene floras which have been progressively enriched by the appearance of several immigrant elements and also by the changes brought in due to evolutionary processes.