In the Eastern Central Himalaya (Langtang Valley) and its southern declivity (Helambu), palynological and phytosociological studies were carried out with the aim of reconstructing the natural vegetation pattern and elucidating the development of replacement communities between the upper cloud forest belt (2000-4000 m a.s.l.), and the alpine belt (ca. 4000-5100 m a.s.l.). According to palynological studies and historical information, the remote area under study was first influenced by man during the 15th century, presumably by hunters who set fire to the forests which were dominated by Quercus semecarpifolia, Tsuga dumosa, Abies spectabilis and Betula utilis. Pteridium aquilinum increased and Juniperus decreased as a result of the fires being set. The only permanent settlement of the upper Langtang Valley (Langtang village) is situated at 3450 m a.s.1. at the transition between the middle and upper cloud forest belt and was founded during the 17th century. A Rhododendron lepidotum dwarf shrub appeared as the first replacement community for the forest. From the continuous influence of fire, forest clearance and grazing pressure, the Rhododendron shrub was partly replaced by pastures and nitrophlous communities in places near the settlement. Permanent settlements never existed at and above the timberline. Here, the anthropo-zoogenous influence is indicated by plants favored by fire or grazing. Under natural conditions, the altitudes between 3000 and 3500 m a.s.l. seem to have been occupied by more Quercus semecarpifolia than was expected based on the present day situation. In addition to this, it was possible to trace a late increase of Abies spectabilis (19th century). The forests at the timberline were dominated by Betula ufilis before and after the beginning of human impact.
