Macroscopic Sedimentary Charcoal as a Proxy for Past Fire in Northwestern Costa Rica

Author

Kyle James Schlachter, University of Tennessee, Knoxville

Date of Award

8-2005

Degree Type

Thesis

Degree Name

Master of Science

Major

Geography

Major Professor

Sally P. Horn

Committee Members

Kenneth H. Orvis, Henri D. Grissino-Mayer

Abstract

Proxy records of fire history offer valuable information on the role fire plays in an ecosystem. Such information can be used to understand the inter-relationships among fire, humans, and the environment. In the past, the forests of Costa Rica were thought to have been spared from significant pre-Columbian forest disturbance; however, paleoecological studies have shown that this notion is false. While the long-term human influence is now recognized in Costa Rica, the nature and extent of human effects in different regions remain poorly documented. Knowledge of pre-Columbian land uses in Costa Rica increases our understanding of the possible impacts of past human disturbances on natural ecological patterns and functioning.

I studied evidence of prehistoric fire provided by fossil charcoal in a sediment core recovered from a lake in northwestern Costa Rica. I developed a new method for the preparation of samples for macroscopic charcoal analysis, and produced an 8000-year-long high-resolution fire record from macroscopic charcoal. My new method of preparing macroscopic charcoal samples involves treatment of sediment samples with 3% U.S.P. cosmetic grade H₂O₂ for 24 hours to deflocculate the sediment and bleach some of the non-charcoal organic matter.

My high-resolution macroscopic charcoal record revealed that fire has been a part of the seasonally dry tropical lowland forest ecosystem in northwestern Costa Rica for the past 8000 years. I found that charcoal influx and fire frequency were greater during the early to middle Holocene and were lower during the late Holocene. After approximately 3600 cal yr BP, macroscopic charcoal influx dramatically decreased. The timing of this decrease corresponds to archaeological and palynological evidence of human occupation near my study site. Charcoal influx remained low until the arrival of European settlers. I suggest that the increase in charcoal influx at this time is associated with converting forested areas into pasture and the introduction of exotic grass.

Recommended Citation

Schlachter, Kyle James, "Macroscopic Sedimentary Charcoal as a Proxy for Past Fire in Northwestern Costa Rica. " Master's Thesis, University of Tennessee, 2005.
https://trace.tennessee.edu/utk_gradthes/4574