Modern pollen and its ecological relationships with the tropical deciduous forests of central Uttar Pradesh, India

摘要

The paucity of modern pollen-rain data from the central part of Uttar Pradesh is a significant barrier to understanding the Late Quaternary vegetation history from the northern region of India. The interplay between extant vegetation and the modern pollen assemblage from both natural and human-induced vegetation types is examined from Lucknow, as an aid for palaeoenvironmental reconstructions. A dataset of 25 surface pollen samples has been documented from the conservation forests of Kukrail, Lucknow (part of Central Ganga Plain). The palynodata reflect the mixed deciduous forest comprising Acacia, Butea, Salmalia, and Syzygium under a warm and humid climate in response to rainfall variations in the region. High monsoonal activity in and around the region is inferred from the presence of the Euphorbiaceae-Moraceae-Syzygium assemblage in the sediments. The marshy and aquatic taxa such as Cyperaceae, Nymphoides and Polygonaceae are strongly suggestive of the perennial waterlogged condition in the area. A striking signal of winter dryness is easily visible in the palynoassemblage, especially observed through Artemisia and Chenopodiaceae. The regular presence of pollen grains of conifers and other broad-leafed taxa including Alnus, Betula, Pinus and Quercus are suggestive of high wind activity from the higher altitudes. Anthropogenic activity is in continuous pace as reflected by the higher frequencies of cereal pollen (14-29%) and Brassicaceae (2-5%). The contrasting frequencies of extant floral taxa recovered in the form of pollen in varied surface samples are indicative of differential pollen production, dispersal and deposition patterns. Therefore, an attempt has been made to precisely observe the behavioural pattern of modern pollen deposition which could in turn help in assessing the expanse of pastoral practices and the depth of deterioration of pristine forests as well as in the reconstruction of past climate and vegetation shifts in Central Ganga Plain, India. A correlation of regional palynodata with other tropical regions of the Indian subcontinent as well as in a global context is required for better interpretation.