Stranglers of the tropics -- and beyond

Stranglers of the tropics -- and beyond
Kudzu -- the woody vine that ate the American South -- soon covers everything in its path. Credit: USGS

Kudzu, the plant scourge of the U.S. Southeast. The long tendrils of this woody vine, or liana, are on the move north with a warming climate.

But kudzu may be no match for the lianas of the tropics, scientists have found. Data from sites in eight studies show that lianas are overgrowing trees in every instance.

If the trend continues, these "stranglers-of-the-tropics" may suffocate equatorial forest ecosystems.

Tropical forests contain more than half of Earth's terrestrial species, and contribute more than a third of global terrestrial carbon and a third of terrestrial net primary productivity, says ecologist Stefan Schnitzer of the University of Wisconsin-Milwaukee.

Schnitzer is co-author with Frans Bongers of Wageningen University in the Netherlands of a paper on lianas in the current issue of the journal .

"Any alteration of tropical forests has important ramifications for , productivity--and ultimately the ," says Schnitzer.

Tropical forests are indeed experiencing large-scale structural changes, the most obvious of which may be the increase in lianas, according to Robert Sanford, program director in the National Science Foundation's (NSF) Division of , which funded the research.

Lianas are found in most tropical lowland forests. The woody vines are "non-self-supporting structural parasites that use the architecture of trees to ascend to the forest canopy," says Schnitzer.

In tropical forests, lianas can make up some 40 percent of the woody stems and more than 25 percent of the overall woody species.

Lianas usually have a high canopy-to-stem ratio, says Schnitzer, "which allows them to deploy a large canopy of leaves above those of the host tree, competing aggressively with their hosts for sunlight, water and nutrients."

Stranglers of the tropics -- and beyond
What a tangled web lianas weave -- in tropical forests, where they're taking over prime real estate. Credit: Stefan Schnitzer

Intense competition from lianas for above- and below-ground resources limits tropical tree growth and survival.

Increasing liana abundance and biomass may have far-reaching consequences for tropical forest community composition, says Sanford.

For example, in a tropical moist forest on Barro Colorado Island, Panama, researchers found that the proportion of liana infestation in the crowns of trees changed from 32 percent in 1967-68 to 47 percent in 1979, to nearly 75 percent in 2007.

The number of trees with severe liana infestation (more than 75 percent of a tree's canopy covered by lianas) increased by 65 percent between 1996 and 2007.

In this forest, liana leaf litter and flower production, compared with that of host trees, increased substantially from 1986 to 2002, says Schnitzer.

Lianas have also overgrown other .

In an old-growth forest surrounding the Nouragues Biological Research Station in French Guiana, scientists found that over the decade from 1992 to 2002, the number of lianas shot up while that of trees fell.

In a forest in the central Amazon, biologists discovered that over the six-year-period from 1993 to 1999, new liana seedlings were 500 percent higher than estimates from previous periods whereas tree seedling recruitment decreased.

But a tree need not live in the tropics to fall victim to lianas.

More than 80 non-native liana species have invaded North America.

Kudzu is joined by English ivy, Japanese honeysuckle and oriental bittersweet, to name a few. Oriental bittersweet is expanding in North American forests, where it has reduced native tree survival.

Stranglers of the tropics -- and beyond
Bauhinia is an all-too-common tropical liana, twining around and competing with forest trees. Credit: Stefan Schnitzer

After hurricane damage in a Florida , invasive lianas rapidly colonized the damaged trees and persisted for many years afterward, reducing numbers of native , shrubs and herbs.

In 50-year-old forests in the Piedmont region of New Jersey, lianas are now abundant.

"A major factor limiting liana abundance in temperate forests is freezing temperatures," says Schnitzer. "Both native and invasive lianas are likely to increase most rapidly in forests that don't have long, cold winters."

For snow-birds--both avian and human--who escape to tropical climes each winter, a strangler-free paradise may be in the woods they left behind.

Explore further

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User comments

Mar 25, 2011
"The long tendrils of this woody vine, or liana, are on the move north with a warming climate."

What warming climate?

One news story asks why the public doubts the global warming story, and another presents this questionable conclusion as a scientific fact!

Remember the "Climategate" revelation of data being hidden and manipulated?

Now we see why Al Gore thought he invented the internet. With help from the UN's IPCC, he showed how to use the internet to promote questionable science as "scientific facts".

With kind regards,
Oliver K. Manuel

Mar 25, 2011
Al Gore started his carbon trading company
a few years before the movie was produced.

wake up.

Mar 26, 2011
Bauhinia purpurea is NOT a liana - it is the Hong Kong Orchid Tree. Which species of Bauhinia is a liana???

Mar 29, 2011
Much of the increase is deliberate. Kudzu and other vines like it are used intentionally for soil improvement. The following is from the wiki page on kudzu:

Kudzu has been used as a form of erosion control and also to enhance the soil. As a legume, it increases the nitrogen in the soil via a symbiotic relationship with nitrogen-fixing bacteria.[8] Its deep taproots also transfer valuable minerals from the subsoil to the topsoil, thereby improving the topsoil. In the deforested section of the central Amazon Basin in Brazil, it has been used for improving the soil pore-space in clay latosols, and thus freeing even more water for plants than in the soil prior to deforestation

This guy is totally and utterly full of bull. This is a good thing, not a bad thing. Reader beware. Never take what a guy looking for funding says at face value.

Mar 30, 2011
"The . . . power of (federal) money is ever present and is gravely to be regarded."

Eisenhower's warning in his 1961 farewell address:

Follow the money and discover (in reverse order) how government science became propaganda . . .

5. Politicians give public research funds to:

4. The US National Academy of Sciences, the UKs Royal Society, the UNs IPCC, and the Alliance of National Academies of Sciences world-wide, who order:

3. Federal research agencies [NASA, DOE, NOAA, EPA ] to ask for:

2. Evidence of specific findings [AGW, H-fusion in the Sun, oscillating solar neutrinos] in exchange for federal research funds, and:

1. Pawns hide and manipulate experimental data purchased with public funds to deceive the public about Earth's heat source - the Sun [a,b,c].

a.) Earth's Heat Source -The Sun:
b.) Neutron Repulsion:
c.) Weather Action:

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