Supplementary material for: A paleothermometer for the Northern Andes based on C3/C4 grass phytoliths

Grass-dominated ecosystems cover ~40% of Earth’s surface with tropical grasses accounting for ~20% of global net primary productivity. C3 (cool/temperate) and C4 (tropical and subtropical) grass distribution is driven primarily by temperature. In this work, we used phytolith assemblages collected from vegetation plots along an elevation and temperature gradient in the Northern Andes (Colombia and Ecuador) to develop a paleothermometer for the region. To accomplish this, we created a transfer function based on the relationship between mean annual temperature (MAT) and the phytolith-based Climatic Index (1-Ic), which is the proportion of C4 grass phytoliths (GSSCP) over the sum of GSSCP. To evaluate how accurately the index reflects C4-C3 grass abundance in vegetation plots, we compared it with semi-quantitative floristic estimates of C4-C3 grass abundance. To further evaluate the 1-Ic index as a proxy for C4-C3 grass abundance, we compared it with corresponding ∂13C values (an independen..., , R, Excel