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Dryad

Isotopic and morphologic proxies for reconstructing light environment from fossil leaves: a modern calibration in the Daintree Rainforest, Australia

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May 05, 2021 version files 48.44 KB

Abstract

Premise: Within closed canopy forests, vertical gradients of light and atmospheric CO 2 drive variations in leaf carbon isotope ratios, leaf mass per area (LMA), and the micromorphology of leaf epidermal cells. Variations in such traits observed in preserved or fossilized leaves could enable inferences of past forest canopy closure and the habitat of individual taxa. However, as yet no calibration study has examined how multiple traits in combination reflect position within a modern closed canopy forest or how these could be applied to the fossil record.

Methods: Leaves were sampled from throughout the vertical profile of the tropical forest canopy using the 48.5 m crane at the Daintree Rainforest Observatory, Queensland, Australia. Carbon isotope ratios, LMA, petiole metric (i.e. petiole-width 2 / leaf-area) and leaf micromorphology (i.e. undulation index and cell area) were compared within species across a range of canopy positions, as quantified by leaf area index (LAI). Key Results: Individually, cell area, δ 13 C, and petiole metric all correlated with both LAI and LMA, but the use of a combined model provided significantly greater predictive power.

Conclusions: Using the observed relationships with leaf carbon isotope ratio and morphology to estimate the range of LAI in fossil floras can provide a measure of canopy closure in ancient forests. Similarly, estimates LAI and LMA for individual taxa can provide comparative measures of light environment and growth strategy of fossil taxa from within a flora. Please be aware that if you ask to have your user record removed, we will retain your name in the records concerning manuscripts for which you were an author, reviewer, or editor. In compliance with data protection regulations, you may request that we remove your personal registration details at any time.