Diversity and palaeoecological significance of non-pollen palynomorph assemblages in East African lake sediments
Year: 2011
Type: article
Abstract: In tropical Africa the palaeoecological visibility of (pre)historical human impact on natural ecosystems is strongly impeded by a dominant signature of climate change at decade-to-century and millennial scales.Better knowledge of the relative magnitude of past human impact is, however, instrumental to properly assess the resilience, and recovery potential, of Africa's natural ecosystems.In this study, we combined taxonomic, ecological and palaeoecological approaches to validate fossil non-pollen palynomorphs (NPPs), i.e. non-pollen micro-remains from fungi and selected groups of algae, vascular plants and invertebrates, as palaeoenvironmental indicators for climate change and human impact on East African ecosystems.We first studied fossil NPP assemblages from the sediment record of Lake Challa, a deep crater lake located near Mt.Kilimanjaro, with the aim to assess the taxonomic diversity of well-defined East African NPPs over the past 25,000 years, and to exploit their stratigraphic turnover during major climate and environmental changes as a guide to their potential as palaeoecological indicators.By comparing 61 fungal spore types with selected pollen curves of common African trees and herbs, and with independent proxies of regional climate (temperature and rainfall) history, we revealed specific habitat requirements of individual NPP taxa.Particularly, changing habitat conditions at the Glacialto-Holocene transition (ca.n,500 cal.yr BP) stand out as the most important event in the distribution of fungal spore types such as Curvularia, Coniochaeta cf.ligniaria, Acrodyctis, Tetraploa aristata, cf.Byssothecium and de types HdV-1032 and HdV-1033.To expand our knowledge ofNPP taxonomic richness in East African lake sediments, we then explored modern NPP assemblages in recently deposited surface sediments of 20 small crater lakes in western Uganda, located along environmental gradients of vegetation (moist evergreen and semi-deciduous forest, wooded and open grass savannah), land use (pastoralism, crop agriculture, plantations) and lake characteristics (basin morphometry, water chemistry and aquatic production).This resulted in a comprehensive inventory of 265 distinct morphotypes, of which 28% could be identified at the species, genus or family level.Focus on the taxonomy of these microfossils resulted in taxonomic descriptions of 187 morphotypes, accompanied by high-resolution photographs and ecological information, when available.
Source: AVRUG-bulletin/Afrika Focus
Institution: Ghent University
Language: English
Subfield: Atmospheric Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
SDGs: Life on land, Climate action
Open Access status: diamond
OpenAlex ID: W2214701571