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A palaeovegetation and diatom record of tropical montane forest fire, vegetation and hydroseral changes on Mount Kenya from 27,000–16,500 cal yr BP

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JournalPalaeogeography, Palaeoclimatology, Palaeoecology
DateAccepted/In press - 18 Aug 2021
DateE-pub ahead of print - 24 Aug 2021
DatePublished (current) - 1 Nov 2021
Volume581
Number of pages14
Early online date24/08/21
Original languageEnglish

Abstract

Fire is an important ecological disturbance in moist tropical forests influencing vegetation composition and structure. Contemporary and historical records of forest fires in mountain forests of Kenya are limited to the past decades and have a strong anthropogenic influence for ignition patterns and fire suppression activities. Palaeoenvironmental geoarchives provide the temporal depth to investigate long-term (multidecadal-to-millennial) changes in fire activity. Here we use a sediment record from the Rumuiku wetland, located in a volcanic crater on the eastern flank of Mount Kenya that was radiocarbon dated and analysed for diatom, pollen and charcoal subfossils to produce a highly resolved time series of local hydroclimatic change, vegetation, and fire; respectively. This study focuses on the time during and following the global Last Glacial Maximum, a time of rapid warming and changing regional hydroclimate with relatively stable atmospheric CO2 and not yet intensive anthropogenic modification of ecosystems. Charcoal and pollen data support associated changes in vegetation-fire centred around 21,500 cal yr BP when Afromontane forests with predominant abundances of Juniperus, Podocarpus and other montane forest trees changed to Hagenia-dominated forests that are relatively more open and adapted to burn more frequently but with less intense fires. These transitions in ecosystem composition, distribution and structure support the important role of fire in driving and maintaining forest composition in the watershed and contributing to the spatial complexity of forests around the mountain. These changes in composition, structure and biomass occurred during a time of rapid Late Pleistocene climate warming, regional hydroclimatic drying, and slowly rising atmospheric CO2 from 27,000 to 16,500 cal yr BP, during and following the conditions of the global Last Glacial Maximum. Temperature, hydroclimate and atmospheric CO2 are well-known drivers of montane vegetation change in the tropics and the role of fire is shown here to be a contributing driver to the spatial heterogeneity of forest patches at long time scales. Vegetation modelling at spatial scales relevant to land management and conservation should include retrospective evidence of the range of drivers of ecological disturbance regimes.

Bibliographical note

Funding Information:
We thank Rose Warigia, Ann Mwende Kaloyo, Rahab Kinyanjui and Joseph Mutua for fieldwork help; Laura Marchant, Esther Githumbi, Lauren Shotter and Maria Gehrels for laboratory work; and Olivier Blarquez, Paramita Punwong and Oliver Heiri for useful discussions. We acknowledge Maarten Blaauw and Steve Juggins for access to computer scripts and software. We also thank the editor and two anonymous peer reviewers whose suggestions led to an improved manuscript. NERC Radiocarbon Facility (NRCF) hosted by the Scottish Universities Environmental Research Centre (SUERC) are thanked for radiocarbon dating of sediment subsamples through award 1226.0407 to Rob Marchant. This research was partially supported by a European Commission Skłodowska-Curie Initial Training Network grant (FP7-PEOPLE-2013-ITN project number 606879 ) and the Adaptation and Resilience to Climate Change (ARCC) project of the Sustainability and Resilience: Tackling Climate and Environmental Changes program funded by the Swedish Research Council (Vetenskapsrådet), Sida, and Formas ( 2016-06355 ), both administered through Uppsala University, Sweden, and awarded to Rob Marchant and principal investigator Paul Lane. The article processing charge was covered by the University of Basel open-access policy agreements with the publisher. The British Institute in Eastern Africa (BIEA) is thanked for logistical support.

Funding Information:
We thank Rose Warigia, Ann Mwende Kaloyo, Rahab Kinyanjui and Joseph Mutua for fieldwork help; Laura Marchant, Esther Githumbi, Lauren Shotter and Maria Gehrels for laboratory work; and Olivier Blarquez, Paramita Punwong and Oliver Heiri for useful discussions. We acknowledge Maarten Blaauw and Steve Juggins for access to computer scripts and software. We also thank the editor and two anonymous peer reviewers whose suggestions led to an improved manuscript. NERC Radiocarbon Facility (NRCF) hosted by the Scottish Universities Environmental Research Centre (SUERC) are thanked for radiocarbon dating of sediment subsamples through award 1226.0407 to Rob Marchant. This research was partially supported by a European Commission Sk?odowska-Curie Initial Training Network grant (FP7-PEOPLE-2013-ITN project number 606879) and the Adaptation and Resilience to Climate Change (ARCC) project of the Sustainability and Resilience: Tackling Climate and Environmental Changes program funded by the Swedish Research Council (Vetenskapsr?det), Sida, and Formas (2016-06355), both administered through Uppsala University, Sweden, and awarded to Rob Marchant and principal investigator Paul Lane. The article processing charge was covered by the University of Basel open-access policy agreements with the publisher. The British Institute in Eastern Africa (BIEA) is thanked for logistical support.

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© 2021 The Author(s)

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