A 165 Thousand Year Fire History from the Neotropical Andes, Colombia

Fire is a global phenomenon with profound and complex ecological, vegetational, climatological and anthropogenic impacts. The natural baseline of a fire regime is a critical foundation on which these impacts can be more fully assessed, however, present knowledge of the natural fire regime remains insufficient and limited empirical studies extend to ages where humans were not present. This leaves outstanding challenges pertaining to the prediction and understanding of past, current and future fire activity. Thus, this thesis presents a ~165 ka charcoal record to reconstruct fire activity and understand its drivers devoid of anthropogenic influence.

A ~58m long composite core of lacustrine sediments from Lake Fúquene (5⁰27’N, 73⁰46’W), Colombia contains sediment accumulated over 284 ka and was previously utilised to reconstruct paleoenvironmental and paleoclimatic changes in the Eastern Cordillera. Using this, a record of macrocharcoal (250 μm) particles of the upper 38.7 m of the core was developed and demonstrates the local history of the fire regime from ~189 to ~27 ka. Fire events, their magnitudes and the charcoal accumulation rates were generated from CharAnalysis 1.1 and assisted in establishing four distinct fire regimes. High variability of fire magnitude and frequency occurred from ~189 to ~114 ka and very low fire activity from ~91 to ~114 ka. Charcoal data was related with pollen and climatic records to address climate and vegetation as potential drivers of fire. An association between biomass burning and temperature is determined owing to the temperature sensitive nature of vegetation surrounding Lake Fúquene. Amplified fire activity arises during greater representation of páramo vegetation, signifying páramo increases probability of burning. Conversely, greater Alnus abundance reduces fire activity, attributed to its fire-resistant traits. Two huge spikes of charcoal at ~81.9 and ~82.4 ka are significant yet is attributed to no clear driver.