Tropical spread of vines attributed to colonization from above

Woody vines known as lianas continue to overgrow trees in the forests of the American tropics. Perhaps their ability to clone themselves by taking root at new sites far from their original roots explains how they gain the upper hand, according to a new report by ecologist Suzanne Rutishauser Yorke and colleagues.

In 2002, Oliver Phillips of the University of Leeds published the first study claiming that vines were becoming more common in the Amazon. The amount of liana leaf litter and the proportion of total leaf litter composed of liana leaves increased significantly between 1986 and 2002 on Panama’s Barro  Colorado Island. Joe Wright and Osvaldo Calderon reported that in 2004.

They are with the Smithsonian Tropical Research Institute

Stefan Schnitzer is a research associate at the institute and associate professor at the University of Wisconsin at Milwaukee. He and his colleagues concluded in a 2011 paper that vines continued to overgrow trees at eight sites from Brazil to South Carolina.

Now the results are in from a long-term study at La Selva biological station in Costa Rica. They show that liana abundance climbed by 15 percent and diameter by 20 percent in old-growth forests but not in selectively logged forests between 1999 and 2007. Colonization by plants from outside the study plots contributed significantly to the increases as lianas in the tops of fallen trees put down new roots.

“We just conducted a follow-up study at La Selva and found that the pace of liana increase from 2007 – 2012 at this site is still high,” said Schnitzer, “And we also found that on BCI, lianas were increasing in density and the number and level of trees infested was on the rise,” he added using the initials for  Barro Colorado Island.

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