Studies on late Quaternary environmental dynamics (vegetation, biodiversity, climate, soils, fire and human impact) on Mt Kilimanjaro

Abstract

Sediments of buried soils from different key areas at Mt Kilimanjaro are studied to reconstruct former and to predict future landscape dynamics on Mt Kilimanjaro. This contributes to a better understanding of local and regional ecosystems, climate, fire and soil dynamics in a larger context, ecosystem dynamics and their reaction on environmental changes, connections and disjunctions of different ecosystems and their role for the development of the biodiversity hot spots in East Africa. Mt Kilimanjaro represents one of the global centres of vascular plant diversity. It is one of the most biodiverse regions on earth. Despite the innate value and importance of the existing ecosystems, we are confronted with the progressing endangerment of these largely unexplored habitats. The implementation of palaeoenvironmental studies is crucial since past processes play a major role in the development of ecosystems and biodiversity. In the present study, investigations of late Quaternary vegetation, climate and fire dynamics are carried out in order to gain a deeper understanding of modern and future ecosystem dynamics. Palynological and multi-proxy analyses of two sediment records are used to reconstruct past vegetation dynamics and to reveal influencing factors. The pollen, charcoal and sedimentological record from the Maundi Crater, located at 2780 m elevation on the south-eastern slope of Mt Kilimanjaro, is one of the longest terrestrial records in equatorial East Africa, giving an interesting insight into the vegetation and climate dynamics back to the early last Glacial period. The WeruWeru pollen record from a montane forest site at 2650 m provides detailed reconstruction of the vegetation response to environmental changes during the Late Glacial and the Holocene. Our results suggest that past climate change caused the vegetation belt to shift along the elevational gradient. The pollen archives reveal shifts in the upper vegetation zones (ericaceous zone and montane forest zone) of at least 1100 m but underline the role of Mt Kilimanjaro as a glacial refuge for montane forest species similar to that of the Eastern Arc Mountains. Fire played an important role in controlling the development and elevation of the ericaceous zone and the tree line around Maundi crater. During the Holocene no anthropogenic impact can be observed, since neither higher fire activity nor a spread of hemerophilic plants is recorded. The modern pollen-rain study along the elevational gradient on Mt Kilimanjaro reveals that it is crucial to establish a modern pollen-rain – vegetation relationship for the calibration and interpretation of a fossil pollen record from a mountain site. The results facilitate the confident use of fossil pollen data to reconstruct more precisely potential vegetation and its dynamics in East African montane forests and also to refine past climate reconstructions in this region for a more accurate comparison of data and modelling.