Modern pollen distribution along a Himalayan elevation gradient in Central Nepal

Abstract

Modern pollen distribution and its relationship to environmental variables in tropical to alpine vegetation zones are investigated to provide a reference for palaeoenvironmental reconstructions and to improve the understanding of pollen dispersal patterns in Central Nepal. A total of 100 samples (from soil and moss) were collected from along an elevational gradient ranging from 173 to 4615 m above sea level. Results show that the alpine zone is dominated by arboreal pollen (AP) and the sub-alpine zone also shows good representation of coniferous taxa pollen such as Pinus, Abies, Tsuga, and Picea along with Ericaceae. The temperate zone has a good representation of Quercus (Evergreen) and Pinus pollen, whereas the sub-tropical zone is characterized by Alnus pollen and agricultural taxa such as Cerealia (planted Poaceae) and Brassicaceae. In the tropical zone, non-arboreal pollen (NAP), mainly Cerealia dominate, reflecting intensive agricultural practices. Shorea is completely silent in pollen representation. A redundancy analysis indicates that elevation is the primary factor influencing pollen distribution in this region. Overall, the pollen data reflect the vegetation distribution but Pinus is over-represented and Shorea is unrepresented, which should be taken into consideration when interpreting fossil pollen in Central Nepal.