European Palaeobotany and Palynology Conference 2026

Conifer leaves can be significant components of fossilized macrofloras and besides being evidence of species presence in the assemblage, they may also contain information about the local paleoenvironment. To strengthen paleoenvironmental inferences based on fossil leaves, we wish to better understand the morphological variability of extant conifer needles. This study focused on three members of the Cupressaceae: Metasequoia glyptostroboides, Sequoia sempervirens, and Taxodium distichum. Mature trees of each species were sampled across the city of Vienna, Austria. Each tree was repeatedly sampled on its most shaded and most sun-exposed sides at one-meter intervals up to 10 meters in height during the spring and summer of 2025. Macromorphological and micromorphological measurements of c. 500 individual branchlets were statistically evaluated to reveal any potential effects of light exposure and (mild) hydraulic gradients. Macromorphological observations indicate that variation is driven by light exposure and canopy position, which supports the continuation of analysis of associated stomatal responses. Disentangling height- and light-related morphological and stomatal variation has the potential to improve paleo-environmental and paleo-CO₂ reconstructions, as well as to enable the confident identification of fossils and sun-needle morphotypes.