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Fire History of Lake Tanganyika (Mahale Coast) Watersheds Reconstructed from Macrocharcoal Records
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  • Haixiang Mao,
  • Andrew Cohen,
  • Nur Sabrina Rosli,
  • Michael McGlue,
  • Murtadha Malallah
Haixiang Mao
University of Arizona

Corresponding Author:maohaixiang625@email.arizona.edu

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Andrew Cohen
Univ of Arizona
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Nur Sabrina Rosli
University of Arizona
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Michael McGlue
University of Kentucky
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Murtadha Malallah
King Abdullah University of Science and Technology
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Abstract

Lake Tanganyika, located in central East Africa, is the longest and second deepest freshwater lake on Earth. Lake Tanganyika’s diverse ecosystem and watershed are under threat today by human activities from extensive deforestation, climate change, and human-induced fires. Therefore, documenting fire and deforestation history in Lake Tanganyika’s surrounding watersheds is crucial for improving watershed management around the lake in the future. Analyzing sediment charcoal records from sediment cores provides high-resolution paleolimnological evidence that reflects the timing and impacts of fire histories and landscape conversion. Macrocharcoal, an incompletely combusted residue that remains when plants materials were burnt by fire, can be transported away from the fire sites and deposited into the lake. We sampled and calculated macro-charcoal (>61 μm) sediment flux from three sediment cores, LT-98-20MR, LT-98-15M, and TANG14-1MC-1A from the lake’s east-central coast. 20MR and 15M are 2.4 km apart, whereas 1A and 15M are 6.97 km apart. We have also compared our results with several previously studied cores from the central part of the lake. Core 15M, which is closest to the shore and has the highest sedimentation rates, showed peaks of charcoal flux from 1830 – 1850, 1896, 1910 – 1914 and 1996 AD based on correlation with a nearby core. Core 20MR, which is further offshore than 15M, has multiple sharp charcoal flux peaks at 1674, 1770, 1848 and 1881 AD, again using correlation with a nearby core. Core 1A, where the watershed has been intensively managed at Kalilani Bay in recent decades (McGlue et al., 2021), shows two significant peaks at 1668 and 1808 AD. The difference in timing of the distributions of sediment charcoal flux peaks from our study indicates these charcoal histories record localized wildfires. Some of these may correlate with the late Little Ice Age dry period in the late 18th – mid 19th C, whereas other more recent ones maybe linked to human activities such as land clearance for cassava cultivation. Low fire frequencies at most sites during the late 19th – mid 20th C may correspond to reduced human populations and disease outbreaks during that period.