Vine invasion? UWM ecologist looks at coexistence of trees ...(stitute and its Center for Tropical Fore...)

With collaborator Stephen Hubbell and graduate students Suzanne Rutishauser and Sasha Wright, Schnitzer is conducting a census of all lianas 1 centimeter in diameter or larger on a 50 hectare plot on Barro Colorado Island nearly 50,000 individuals have been tagged, mapped, measured and identified to species.

The researchers will match a map of liana abundance on their Panamanian plot with an existing dataset on 25 years of tree growth and mortality for nearly a quarter million trees and saplings. They will also conduct a separate study of liana removal in an adjacent forest. In that study, they will quantify how lianas contribute to forest-level CO2 sequestration.

Thriving in drought

"It appears to be true that lianas grow more rapidly at higher levels of C02," Schnitzer says. "But there could be other explanations for the increase in lianas, too. Weather could be a factor."

His hypothesis is that tropical lianas thrive during seasonal droughts, when trees suspend their growth and lose their leaves, giving the lianas a competitive advantage in those locations. In fact, he found the growth rate of lianas is seven times that of trees in dry conditions, compared to only twice that of trees in the rainy season.

One reason may be that lianas have a more efficient root system than trees, but Schnitzer says more information is needed. He and his collaborators are using probes inserted into lianas to collect data on the flow of the water inside the vines' vascular system throughout the year in order to determine how lianas respond to drought.

"If lianas can grow far more than trees during seasonal droughts, then global increases in drought from such events as El Nio or La Nia may be responsible for the documented inc
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