LEAF SIZE AND SHAPE AS A PALEOCLIMATE PROXY: INVESTIGATING TAPHONOMIC BIASES WITHIN SPECIES

Abstract For over a century, leaf size and shape have been used to reconstruct aspects of climate related to temperature and precipitation. These methods are typically calibrated with complete leaves from living forests. An understudied issue is how appropriate these calibrations are to incomplete leaf compression fossils that dominate most fossil leaf assemblages. We sought to test the fidelity of leaf-climate methods with leaves sampled from three taphonomic stages (fresh, surface litter, and buried litter) in two temperate forests. We sampled environments that commonly contain fossil leaves in the geologic record: swamp and river margins. We find that in comparison to fresh leaves, conspecific leaves from the surface litter and buried litter are progressively smaller. As a result, paleoprecipitation estimates using leaf size and shape may be underestimated by as much as 23%. In contrast, traits common in temperature models (e.g., size and number of leaf teeth) show little within-species taphonomic biasing.