Figure 3. Carbon isotope signatures (δ¹³C values) of soils at increasingly greater depths in two soil pits (Gardner and El Caco) on Española Island, Galapagos.

Radiocarbon dating indicated that depths of 40 cm are approximately 500 years BP; therefore, samples below the 40 cm depth are grouped to show pre-disturbance averages. Points are δ¹³C values of the island’s dominant woody plants (Bursera, Cordia, Croton, Parkinsonia, Prosopis) and herbaceous plants (Cyperus and Paspalum) as well as cactus (Opuntia) (averaged across 10 samples of each, with standard errors for all means too miniscule to be evident in this graphic).