Stable Isotope Ratios of Carbon in Phytoliths as a Quantitative Method of Monitoring Vegetation and Climate Change

Abstract

Abstract The 13 C/ 12 C ratios of occluded carbon within opal phytoliths from the northern Great Plains show potential as a basis for paleoclimatic reconstruction. A significant correlation exists between the carbon isotopic composition of a host plant and that of the organic matter in its phytoliths. The 13 C/ 12 C ratios for phytoliths from surface layers of soils along climatic gradients reflect the current proportions of C 3 and C 4 plants. Variations in the δ 13 C values of phytoliths with soil depth are caused by a variety of processes: burial of soil surface by dust, bioturbation, and possible illuviation by percolating water. Also, contributions of phytoliths by dust and roots have unknown isotopic effects. The δ 13 C values of phytoliths from soils increase with decreasing 14 C age, suggesting that the proportion of C 4 plants in this region has increased during the Holocene. Phytoliths of apparent mid-Holocene age suggest exclusive dominance by C 4 plants which agrees with paleoclimatic interpretations of an arid middle Holocene climate.