Tree leaves can yield climate history

WACO, Texas, April 18 (UPI) -- Using size and shape traits of leaves to reconstruct past climates over 120 million years is more accurate than other current methods, U.S. researchers say.

Geologists at Baylor University and Wesleyan University collected thousands of leaves from different species of plants from 92 climatically different and plant-diverse locations on every continent except Africa and Antarctica, a Baylor release said Monday.

"Paleobotanists have long used models based on leaf size and shape to reconstruct ancient climates," Daniel Peppe, assistant professor of geology at Baylor, said. "However most of these models use just a single variable or variables that are not directly linked to climate, which obviously limits the models' predictive power."

Using multiple variables, the researchers developed mean annual temperature and mean annual precipitation models and compared them to nine well-studied fossil floras.

The scientists found leaves in cold climates typically have larger, more numerous teeth, while leaves in wet climates are larger but have fewer, smaller teeth.

The relationships between climate and leaf size and shape is affected by leaf type -- deciduous versus evergreen -- local water availability and the evolutionary history of leaf types, the researchers said.

"Our study demonstrates that the inclusion of additional leaf traits that are functionally linked to climate improves paleoclimate reconstructions," Peppe said.