RECONSTRUCTING PALEOGRASSLAND COMPOSITION USING GRASS (POACEAE) CUTICLE

Carbon isotopic analysis of bulk lake sediment provides a first-order approximation of the relative abundance of C₃ vs. C₄ plants surrounding a basin. However, such analysis does not directly address paleograssland composition, as contributions from arboreal C₃ plants may hinder interpretation. Comparison of the bulk sediment carbon isotopic signal with carbon isotopic values of grass cuticle extracted from the same sediments allows evaluation of the integrity of the bulk sediment carbon isotopic signal as a record of paleograssland composition. Concomitant analyses of pollen as well as grass cuticle morphology further refine reconstructions of vegetation composition and allow not only recognition of grassland vs. non-grassland communities, but in the case of grass-dominated ecosystems also provide information regarding specific grass genera and species present on the landscape. Application of this methodology to Holocene sediments from Lake Bosumtwi, Ghana demonstrates the effectiveness of this multi-proxy approach in reconstructing vegetation change and understanding the paleoclimatic implications of such changes.