Regan E. Dunn

Paleoecology & Paleobotany

Cuticle-based LAI reconstruction

A large part of my present and future research goals are to make the LAI proxy widely applicable to other types of plant remains, principally organically preserved leaves.

Leaf cuticle fragment from the Paleocene, Hanna Basin, WY
Leaf cuticle fragment from the Paleocene, Hanna Basin, WY

The rLAI method as originally constructed uses phytoliths, but phytoliths are sensitive to oxidation and dissolution and they do not preserve in every depositional environment. Hence, for maximum utility of the rLAI method, the proxy must be expanded to other types of fossils such as organically preserved leaf epidermis (leaf cuticles), which are commonly found in sedimentary deposits.

Examples of leaf cuticle preserved at Emerald Creek,
Examples of leaf cuticle preserved at Emerald Creek, “Clarkia”, ID

While the anatomical structures (epidermal cells) of interest are the same in the two types of fossil preservation (phytolith and cuticle), it is unknown if certain biases, such as cuticle shrinkage or the over-representation of more durable sun leaves may change the distribution of cell morphologies represented by the leaf cuticles. This research will determine if cell morphology of the cuticles is related to LAI in the same way as phytoliths. To test this idea, I am studying cuticle fragments from soil samples collected in Costa Rica and I will be enhancing this soil collection with samples from New Zealand, Ecuador, Bolivia and Argentina that I will collect in the winter of 2016. Results thus far confirm that a cuticle specific model for calculating rLAI will be needed. Stay tuned for exciting developments!

If successful, this work would allow a completely new view of habitat change across important events in Earth history for example, habitat changes across the K-Pg extinction, the Paleocene-Eocene Thermal Maximum, hominid evolution in Africa, Pleistocene glaciation, and anthropogenic change in the Holocene.

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