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Title: Central African lowland forest resilience to fire disturbance and climate change : answers from the past
Author: Tovar Ingar, Carolina
ISNI:       0000 0004 6063 2894
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2015
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Tropical rainforests have been and will remain subjected to various natural and human pressures, which have already led to rainforest degradation and disappearance. This thesis aims to improve our current knowledge of the likely future trajectory of the persistence of the tropical African rainforest under climate change and fire impact through reconstruction of past vegetation and burning dynamics using palaeoecological records from sedimentary sequences. I used several types of palaeoecological proxies (i.e., fossil charcoal, phytolihs, and fossil pollen) from sediment records collected in the Sangha River region, in the northern part of the Republic of Congo, to explore past fire dynamics between four different forest types (i.e. mixed forest, swamp forest, Marantaceae forest and monodominant Gilbertiodendron forest), and to reconstruct the vegetation history of two endemic types of African forest i.e., the Marantaceae forest and the monodominant Gilbertiodendron forest, for the last 2500 cal BP. Lastly, I combined fossil pollen records from the literature with ecological niche models (ENM) to explore the relationship between climate and rainforest distribution over the last 6000 cal BP. My results demonstrate that the past frequency of predominately human-induced fires was significantly higher in areas currently covered by Marantaceae forest compared to areas currently covered by any of the other forest types, and that this high frequency of fires has therefore contributed to the maintenance of Marantaceae forest. Thus, the two Marantaceae forest sites I studied are of recent formation (around 450-600 cal BP) and were previously covered by the mixed forest type. Out of all the considered forest types, the mixed forest is the most vulnerable to both climatic and fire disturbances while the monodominant Gilbertiodendron forest has been most resilient to past climatic events, with no major change in its composition for the last 2700 cal BP. I also found that monodominant Gilbertiodendron forest has persisted during this time period mainly under the absence of burning which supports the hypothesis of long term minimal burning disturbance being a key factor for monodominant forest persistence. At the biome level, my results show that the relationship between climate and African rainforest has partially shifted over the last 6000 years, thus opposing the idea of climatic niche conservatism of this biome in the African continent. This thesis provides new information of the past ecological responses of African rainforest to major environmental disturbances. African rainforests represent a globally important and largely understudied forest region, and my thesis offers fundamental insights into its ecology and biogeography.
Supervisor: Willis, Katherine J. ; Breman, Elinor Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available