Fig. 5.

δ¹⁸O of modern and tar pit Juniperus wood α-cellulose and calculated relative humidity from ¹⁸O values. (A) δ¹⁸O of α-cellulose (δ¹⁸O_cell) for glacial (tar pit) and modern Juniperus. x-axis errors indicate the 95% confidence interval for ¹⁴C age. For modern Juniperus, the symbol represents the average δ¹⁸O_cell of eight J. californica trees from Los Angeles, and the y-axis error indicates ±1 SE. (B) Relative humidity estimates by using the Roden et al. (13) tree-ring cellulose model based on δ¹⁸O_cell from modern and glacial wood cellulose that is shown in A (see Materials and Methods for model parameters and validation).