title: Late Pleistocene and Holocene vegetation, fire and climate dynamics in the Lake Victoria area
Creators: name: Temoltzin Loranca, Yunuén
Publisher: name: Universität Bern
Year: 2024
Subjects: subject: 550 Earth sciences &amp; geology
subject: 570 Life sciences; biology
subject: 580 Plants (Botany)

description: This PhD thesis work emerged as part of the large Swiss National Science Foundation project – 20,000 years of evolution and ecosystem dynamics in the world’s largest tropical lake reconstructed from sediment cores, fossils and ancient DNA– with grant number 183566, devoted to understanding fish evolution under strongly changing environmental conditions. The project explores the evolution and ecosystem dynamics in Lake Victoria, as reconstructed from sediment cores, fossils and ancient DNA. In particular, this PhD project explores palaeoecological proxies and establishes high precision 14C chronologies with the aim of characterizing and assigning an accurate timing to the environmental changes in the Lake Victoria ecosystem before significant human disturbance. At the same time, this research is also dedicated to address the current palaeoecological research gaps in the Lake Victoria area. For instance, the lack of a comprehensive analysis of macrocharcoal. Although previous studies have examined aspects of fire history, there is a need for a continuous record spanning the latest Pleistocene and the Holocene, which would enable us to identify shifts in fire regimes and identify the primary sources of fire and their impacts on terrestrial vegetation under strongly varying climates. Another gap in current research, pertains to the understanding of ecosystem responses to climate during the savanna–rainforest transition. While previous studies have provided valuable insights, there is a lack of detailed and high–resolution pollen records in this critical period. Therefore, this thesis contains two main chapters dedicated to tackle these gaps, Chapter II: A chronologically reliable record of 17,000 years of biomass burning in the Lake Victoria Area, and Chapter III: Ecological long-term successions around Lake Victoria from the latest Pleistocene to the onset of the African Humid Period.
Chapter II (Temoltzin-Loranca, et al. 2023a) strives to achieve two primary aims. First, to provide a novel chronology for three new sediment cores from the deepest part of Lake Victoria, based predominantly on macroscopic charcoal (>200 μm). This chronology has been validated by the biostratigraphy (pollen), over a three-core transect. Second, to provide the first continuous macroscopic charcoal analysis reconstructing the Late Glacial and Holocene fire history. Such novel (e.g. charcoal, pollen) and established palaeoclimate data are used to discuss the long-term linkages between climate, fire, and vegetation at a biome level in the Lake Victoria area.
Given that vegetational changes happen in relatively short time spans, high-resolution studies are needed to understand major ecosystem transitions. In the Lake Victoria basin, major biome reorganizations occurred during the late Pleistocene and the early Holocene (Beuning, 1999; Kendall, 1969; Temoltzin-Loranca et al., 2023). Therefore, in Chapter III (Temoltzin-Loranca, et al. 2023b), the first high-resolution pollen record from Lake Victoria, covering the late-glacial and early Holocene, is used to assess the major vegetation and ecosystem transformations and elucidate their corresponding responses to climatic fluctuations and disturbance.
Our hope is that this PhD thesis serves as a valuable reference for those interested in exploring the fascinating niche of East African palaeolimnology and palaeoecology, and to contribute to the advancement of tropical research as a whole. In addition to bridging the gaps in knowledge, our study also attests to the importance of innovation and method adaptations in the pursuit of scientific understanding.