Research Tracks

A publication of the Office of the Vice Provost for Research at Baylor University

February 12, 2014
by Baylor OVPR
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Turning over an old leaf: Baylor geologist finds climate clues in fossilized plants

Thanks to modern record-keeping, finding out what the weather was like at any time in the recent past is a fairly simple proposition. Gathering data on the earth’s climate from millions of years ago, however, is another matter. Since there is no way to directly measure ancient climatic conditions, researchers make inferences about ancient environments based on currently available evidence, such as fossils.

Dr. Daniel Peppe collects fossil samples in the field.

Dr. Daniel Peppe collects fossil samples in the field.

Research by Dr. Daniel Peppe, an assistant professor of geology in Baylor’s College of Arts & Sciences, has revealed a new set of tools for reconstructing ancient ecosystems using fossilized fern leaves. The study, published this month in the American Journal of Botany, suggests that fern fossils can reveal environmental data from earlier periods compared to existing methods, which rely on plant groups with a shorter fossil record.

“We know that we can use the size and shape of leaves to reconstruct climate and ecology,” Peppe says, “but that analysis is mostly focused on angiosperms — flowering plants like modern trees. The fossil record for angiosperms goes back about 150 million years, but there is a much longer fossil record for other types of plants, particularly ferns.”

To tap into that longer fossil record, Peppe and an international team of collaborators studied 179 modern fern species, seeking a connection between the plants’ features and the environments in which they grow. Their analysis revealed a relationship between ferns’ biomechanical features — the ratio of stem thickness to leaf mass — and the life span of the plant’s leaves.

A fossil of the fern species Onoclea sensibilis collected from the Fort Union Formation in the Williston Basin in North Dakota. The fossil is Paleocene in age and around 65 million years old (photos courtesy of Dr. Peppe).

A fossil of the fern species Onoclea sensibilis collected from the Fort Union Formation in the Williston Basin in North Dakota. The fossil is Paleocene in age and around 65 million years old (photos courtesy of Dr. Peppe).

Peppe says that understanding the growth pattern of a plant and the life span of its leaves reveals information about the type of environment the plant lived in.

“A slow-growing plant would indicate an environment where the plants are not often disturbed, so they are able to put more resources into growing larger leaves that live longer,” he says. “Faster-growing leaves with shorter life spans would suggest the plant is in an area where it would be frequently disturbed by flooding or other disturbances.”

The researchers also found that ferns differ from flowering plants in the relationship between stem width and leaf mass, which Peppe says may be related to differing evolutionary histories or differences in the way the plants use their stems for support and to carry water and nutrients to and from the leaves.

Peppe’s work was supported in part by a grant from the Young Investigator Development Program in the Office of the Vice Provost for Research.  Click here to read the full paper in the American Journal of Botany.