permaculture

["Lawrence F. London, Jr." <lfl@intrex.net>]

Probably time to do preemptive maintenance if you have these on your 
property: Kudzu, wisteria, Bermuda grass,
trumpet vine, honeysuckle, Johnson grass, Pennsylvania smartweed, crabgrass 
and various mystery weeds and,
of course Poison Ivy and Oak - LL
--------------------------------------------------------------------------------------------------------------

Pumped-up Poison Ivy: Carbon dioxide boosts plant's size, toxicity: Science 
News Online, June 3, 2006
<http://www.sciencenews.org/articles/20060603/fob1.asp>

Pumped-up Poison Ivy: Carbon dioxide boosts plant's size, toxicity
Susan Milius

Whatever troubles climate change might bring to the world's other species, rising carbon dioxide in the atmosphere could 
be the best thing yet for poison ivy.

BAD VINES. Poison ivy grows unusually fast when carbon dioxide in the atmosphere reaches concentrations expected in 
forests by about the year 2050.
J. Blanchard

An outdoor experiment mimicking the carbon dioxide rise predicted for this century found that poison ivy vines grew more 
than twice as much per year as they did in unaltered air, says Jacqueline E. Mohan, now of the Marine Biological 
Laboratory in Woods Hole, Mass. That growth streak is nearly five times the increase reported for some tree species in 
other analyses.

More bad news: The jolt of carbon dioxide also boosted the most-toxic forms of poison ivy's rash-raising oil, Mohan and 
her colleagues report in an upcoming Proceedings of the National Academy of Sciences.

"It's a sobering example that rising carbon dioxide can favor pests and weeds, those plants we'd least like to see 
succeed," comments climate-change ecologist Bruce Hungate of Northern Arizona University in Flagstaff.

People burning fossil fuels release carbon dioxide into the atmosphere. As the atmosphere gains carbon dioxide and other 
so-called greenhouse gases, it traps more of the sun's heat.

Biologists have wondered whether this carbon boost might work as aerial fertilizer for plants. Earlier lab experiments 
found plants growing exuberantly with extra carbon dioxide, but these tests provided abundant water and nutrients.

For more-realistic tests, researchers have set up treetop-high pipes that blow either regular air or extra carbon 
dioxide over landscape patches in various ecosystems around the world. For 6 years, Mohan and her colleagues monitored 
poison ivy and the other plants growing within circles of such pipes in a pine forest monitored by researchers of Duke 
University in Durham, N.C.

The poison ivy vines thrived with about 50 percent extra carbon dioxide, showing extra photosynthesis and more-efficient 
water use.

These vines produced the same concentration of the toxic oil urushiol as the plain-air vines did. However, for the 
poison ivy receiving extra carbon dioxide, about 20 percent of the oil was in chemically unsaturated forms, whereas the 
plain-air ivy produced 15 percent unsaturated urushiol. The unsaturated forms are more likely to provoke painful skin 
reactions in people.

Other studies have suggested that vines may be big winners in a high–carbon dioxide future, says Mohan. Vines don't 
spend much of their carbon harvest on trunks or other supports, so the carbon windfall can go directly into new leaves, 
which collect yet more carbon and sunlight.

An increased abundance of vines, which can choke out trees, could change 
forest dynamics, Mohan says.

Forest honeysuckle vines increase their growth in air that's high in carbon dioxide, says Rich Norby, who directs a 
pipe-circle experiment at Oak Ridge (Tenn.) National Laboratory. However, he predicts that even poison ivy's gangbuster 
growth will eventually hit some limit, such as available sunlight.

The pipe-circle experiments can't mimic all the factors influencing plants in real forests. Mohan protected her 
experimental poison ivy plants from white-tailed deer and other browsing animals, notes plant physiologist Hendrik 
Poorter of Utrecht University in the Netherlands. Yet plants growing in abundant carbon dioxide typically have low 
protein content, so Poorter speculates that animals might actually eat more of them to get adequate nutrition.

Bigger, more-toxic poison ivy is a serious concern, says Paul Beggs of Macquarie University in Australia. It's another 
factor to add to his tally of the extra misery that climate change might bring to people with allergies. For example, 
certain pollen counts are likely to go up, so allergy seasons could drag on longer, he says.

Mohan had never developed a rash from poison ivy before she started the study. "I 
get it now," she says.