Alpine grassland palaeoecology of the Virunga Volcanoes, East Africa: A new phytolith record from Mt. Muhavura
Loading...
Date
2017
Journal Title
Journal ISSN
Volume Title
Publisher
Quaternary International
Abstract
This study presents a first attempt at using phytoliths from a high-altitude crater lake as a palaeoecological
tool at a tropical montane site. Mt. Muhavura (4127 m asl) at the border of Uganda and
Rwanda is part of the Virunga volcanoes located in the Albertine Rift, one of the most biodiverse areas in
Africa. To investigate the potential of phytoliths to record grassland history in an Afroalpine environment,
a unique and little studied ecosystem, we analysed the phytolith content of 37 sediment samples from a
159 cm sediment core from the crater lake at the summit of Mt. Muhavura representing the last ca.
2400 years BP. Ten plant species from the Alpine belt were also analysed for their main phytolith
morphotypes. Phytoliths from the sediments were grouped into 12 main categories and the most
frequently occurring individual morphotypes were bilobate (33%), oblong (16%), elongate (17%) and
globular psilate (13%). The phytolith assemblage consists predominantly of phytoliths characteristic of
grasses (70%). A literal interpretation of the results would be that Panicoideae grasses (mainly C4) that are
characteristic of warm and wet climate and C3 Pooideae subfamily grasses characteristic of cold climate/
high altitude have co-existed throughout the late Holocene in this belt. As only C3 cold climate grass
subfamilies are known to occur at this altitude today, the abundance of short cell phytoliths (bilobates)
typical of Panicoideae grasses in the lake sediments at this altitude presents a new perspective to the
phytolith discussion. The C3 Pooideae grasses analysed did not produce bilobates. In this study, the
phytolith index, Ic that is used as a proxy of past grass subfamily dominance is not representative of the
taxonomic significance for which it is known. This study suggests that caution needs to be taken when
using bilobate morphotypes and the Ic as indicators of grass subfamily dominance at high altitude on
East African mountains as the bilobates may not be taxonomically representative of the grasses for which
they are typically known. This highlights the inherent problem of phytolith redundancy even at an
altitude where C3/C4 grass distribution is better delineated.
Description
Keywords
Phytoliths, Afroalpine grassland, Palaeoecology, Mount Muhavura, Virunga volcanoes, East Africa
Citation
Murungi, ML, McGlynn, G., & Lejju, JB (2017). Alpine grassland palaeoecology of the Virunga Volcanoes, East Africa: a new phytolith record from Mt. Muhavura. Quaternary International , 434 , 102-116. http://dx.doi.org/10.1016/j.quaint.2016.01.015