Thursday, August 3, 2017

With a Name Like Tree of Heaven, You Know Already It's Invasive #Science #Botany

Photographer unknown but we're reasonably sure this was not shot in Heaven so the tree is therefore an imposter.

Tree-of-heaven—or Ailanthus—is an invasive triple threat, according to a team of plant pathologists. The species produces seeds early in its lifespan, tends to make millions of viable seeds during its life, and continues to produce seeds for decades and, in some cases, for more than a century.

In a study, researchers, who report their findings in the current issue of Forests, found that an Ailanthus tree that lives around 40 years can produce approximately 10 million seeds during its lifetime, while Ailanthus trees that live over a 100 years can produce about 52 million seeds.

Little was known about the actual lifespan and seed viability—the percentage of seeds that germinate—of Ailanthus, a species that is now considered a growing invasive threat in numerous spots in the United States, according to Matt Kasson, assistant professor of forest pathology, West Virginia University, who began his study of Ailanthus at Penn State. He added that the species' prolific ability to reproduce is thought to be key to its invasive success.  Tree-of-heaven's prolific seed production adds to its invasive potential

The technique of producing zillions of seeds to achieve reproductive success seems like the way to do it but there's another twist.

Kristen Wickert, a doctoral candidate in the division of plant and soil sciences, also at West Virginia University, who worked with Kasson, said that the viability of the Ailanthus varies. For example, a 7-year-old tree, one of the youngest trees in the study, had 78 percent of its seeds germinate, while one of the oldest, a 104-year-old tree, had 66 percent of its seeds germinate.

Few species—native or invasive—in the U.S. compare to Ailanthus' seed viability, according to Wickert. Only 9 percent of a tulip poplar's annual seed production is viable, for example. She added that Ailanthus is different from other tree species because of its ability to maintain seed viability over its lifetime.

- PO

As plants go, the Tree of Heaven is stone evil since it knows other magic tricks as well.

"It's also allelopathic, which means it produces chemicals that inhibit the germination of other native species that are growing in the same forest," said Kasson. "So, in addition to its ability to grow rapidly and produce seed early, it has the ability to stunt the growth of those competitors."

- PO

There you go ... if you can't compete fairly then kill off the opposition.

It's not a trivial matter since the invasive species are having significant effects on native populations.

"The invasive spread of Ailanthus is more significant now," said Davis, who also worked on the study. "It's right at the top of the list of invasive species in Pennsylvania, including trees like the Norway maple, and shrubs like honeysuckles. All these invasive species are important now because they are really affecting the forests and forest regeneration, especially."

- PO

Clark Kent:  is the problem that Tree of Heaven's seeds are so healthy or that the native tulip poplar's seeds are such wimps?

Good job on investigative reporting, Clark Kent, since we like it when investigators look for answers rather than inventing them for the six o'clock news.

The tulip poplar is probably the example of the wimpiest performer they know so they ask us to assume all native species are also that wimpy.  That aspect is finger painting but the comparison between the two species is striking.  One thing's for sure:  if the Tree of Heaven ever turns up near a tulip poplar then the poplar can give up its dreams of ever having a family of little poplars.

You can thank 18th Century gardeners for this invasive menace.

"It came to the United States, in the Philadelphia area, in around 1784," said Davis. "It was strictly brought in as an ornamental—it's a beautiful tree that became popular in the Philadelphia area. Initially, collectors just brought in cuttings from male plants, but then they brought in seeds—and eventually, it took off."

- PO

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