Tree of Heaven on Penn State campus

From an Article by Kara Holsopple, The Allegheny Front, August 11, 2017

There’s an invasive tree that is becoming a threat to Pennsylvania’s forests. And it’s one that you see all the time. Ailanthus altissima, better known as tree of heaven, is a tough urban tree that sprouts out of sidewalks. It also happens to be the tree from the book A Tree Grows in Brooklyn. The tree came to the U.S. from China by way of England in the 1700s. And since then, it has thrived. The tree of heaven is found in 40 states, including most of Pennsylvania.

Matt Kasson is an assistant professor of forest pathology at West Virginia University. He’s been studying the tree for more than a decade, and his latest research was recently published in the journal Forests. The study was co-authored by Kristen Wickert, Eric O’Neal and Dr. Don Davis.

Kara Holsopple spoke to him about what he and his team have learned about the tree’s spread.

Kara Holsopple: Your newest research clues us into why this non-native tree has done really well. What did you find?

Matt Kasson: We’ve known for a while now that Ailanthus is pretty aggressive in colonizing the landscape. But what was unclear to us, and really the motivation behind the study, was to figure out its reproductive potential. If you drive down the highways right now you could see these brilliant red to orange colored seed clusters, prolific seed production on individual trees. But we wondered how much seed could these trees actually produce in a single year and over a lifetime.

KH: And what did you find?

MK: We found that there are some exceptionally reproductively capable individuals across the landscape. We found one tree in particular on the campus of Penn State University that routinely puts out about 700,000 seeds a year, and that’s been doing so for almost a century. So the cumulative seed production of that tree is somewhere north of 50 million seeds over its lifetime. Now that’s an exceptional tree. But we found that on average a tree that lived 40 years and was reproductively capable during that window could produce upwards of 10 million seeds.

LISTEN: “Tree of Heaven Creates Hell for Native Forests”

KH: Your study mentions viability. That’s the success of the seed once it gets into the ground if it’s going to become a tree or or not?

MK: I think viability is a really important aspect because if a tree can produce a million seeds per year, and viability is 3 percent, that’s not a lot of reproductive capacity. But if viability is north of 70 percent like we found on a few of our individuals including this 104 year old individual in Pennsylvania, the potential for producing a lot of progeny over a lifetime is exceptional.

KH: So why is this tree’s kind of super reproductive power and it’s spread a problem?

MK: It wasn’t always a problem. And I think the ways we manage land and landscapes have changed over time. Following another invasive pest, the gypsy moth, we saw widespread land clearing which really set up these forests for Ailanthus. Gypsy moth has been here since the 1800s and it started to devastate forest in Pennsylvania and throughout the Appalachian region in the late 70s to early 80s. We saw widespread salvage harvesting in the aftermath of this gypsy moth defoliation because the defoliation was so severe that it actually killed a lot of the oak trees that were occupying these ridge tops in South Central Pennsylvania and elsewhere throughout the mid-Atlantic. So one reproductively capable female tree at the edge of this clear cut seeded in the hole clear cut. And now you’re left, not with native trees regenerating, but a whole entire stand of invasive trees.

KH: Is this something that’s worrying for foresters?

MK: Absolutely. Tree of heaven, not only can outcompete native species that might seed into those same clearings, but it also produces compounds that inhibit the germination of native plants. It’s called allelopathic and what it does is it produces these compounds that make the site more suitable for itself to regenerate and less suitable for native plants. If we think about the spotted lanternfly which is a new pest that’s just been found in Pennsylvania, it actually requires Tree of Heaven to fulfill its lifecycle: It feeds on the foliage, it lays eggs on the stems, and it’s a real threat to the grape industry. Tree of heaven is pretty well established throughout most of the counties in Pennsylvania with the exception of a few of the northern tier counties. So, in that sense, it could follow tree of heaven up towards Erie and up to New York into the Finger Lakes region where it could directly threaten and impact the grape and wine industries in those regions.

KH: How can you get rid of them? Can you cut them down? What are some of the ways that you can remove them?

MK: I’ve been working on biological control using native fungi to kill Tree of Heaven in these forest settings for about a decade now. But there’s still plenty of stands of Atlantis that haven’t been controlled. And until they’re removed, whether it be through biological control or chemical applications or mechanical removal, they’re going to continue to be under-productive forests that supplant native species and prevent future generations of native forested stands from establishing.

KH: Tree of Heaven is commonly thought of as an urban tree. How did they move into the forest?

MK: That’s a good question. For a long time it just kind of hung out in Philadelphia and New York is kind of a botanical oddity passed around among early botanists and then seed producing trees were established and soon seedlings were available through a lot of the nursery trade and followed the railroad corridors east and west. We noticed a huge spike in the spread of tree of heaven in Pennsylvania following the completion of the Horseshoe Curve which connected the east and western part of the state.

Tree of heaven moved along those transportation corridors much like they move along our interstate highways now. But as to how they got in the forest, with building of roads and things like that, we see movement of invasive species whether it be through gravel or just that there’s a lot of exposed soil which allows prolific seed producing species to establish.

There was a recent study done out of Penn State that showed that these Marcellus shale well sites are now being taken over by a number of invasive plant species. We predict that tree of heaven will follow suit because it does occur up in those northern tier counties but they’re not really widespread as of yet. But with all this new road building and road construction to support the gas industry, I think we’ll see a lot more spread of these invasive species that are common throughout the the southern part of the state.

>>> Matt Kasson is an assistant professor of forest pathology at West Virginia University.

Colorful Tree of Heaven seed pod

Japanese stiltgrass spreading in WV & PA

From an Article by Leon Valsechi, Centre Daily News, August 4, 2017

Researchers at Penn State have discovered in a recent study that Marcellus Shale fracking activity (adds to) the spread of invasive, non-native plant species.

The findings, published in July in the Journal of Environmental Management, are a result of research that began in 2012 and focused on 127 natural gas well pads on state forest land in the north-central part of the state.

Lead researcher Kathryn Barlow, a doctoral candidate in Penn State’s department of plant sciences, said the team found that 61 percent of the wells studied have at least one invasive, non-native plant species growing around the edges of the well pads or along the sides of the access roads.

Of the wells that are being colonized by invasive plants, 19 percent have more than one non-native plant, such as Japanese stiltgrass, reed canary grass and crown vetch, according to the study.

“We suspected that with any disturbance to a forest and human activity, there’s going to be spread of invasive plants, so it’s not surprising that we found them,” Barlow said. “But we felt that it would be important to quantify and better understand the colonization so far.”

As the research progressed, the team began discussions with the Department of Conservation and Natural Resources on a potential collaboration effort to advance the efforts of both parties to understand non-native plant behavior.

“These conversations led ultimately to a monitoring protocol that was adopted by both the bureau of forestry and Penn State,” Kelly Sitch, an ecologist at the state Department of Conservation and Natural Resources, said in an email.

The protocol helps DCNR’s gas monitoring teams to track invasive plants on the 180 well pads, 28 freshwater impoundments, 17 compressor stations and 34 infrastructure pads located on state forest land, Sitch said.

In addition to tracking the plants using the survey protocol, Penn State analyzed the role fracking vehicle traffic plays in spreading the seeds.

Fracking or hydraulic fracturing is the process of drilling into the earth and injecting fluid at high pressure into rock, fracturing the formation and releasing natural gas. To reach the desired well depth, about 1,200 one-way truck trips are required to deliver the fluid needed for the process, Barlow said.

The Penn State team measured how far the invasive plant seeds can blow based on the wind speed created by a passing vehicle. The team also discovered that the seeds can stick to the undercarriage of the vehicles, which Barlow said accelerated the spreading rate of the plant colonies.

While the study focused on fracking well pads and access roads, Sitch said the gas activity is not the lone propagation source of the invasive plants in the state forests.

“Any activity that results in the opening of the forest canopy or soil disturbance increases the likelihood of colonization by invasive plants,” Sitch said. “Certainly, as a result of the disturbance caused by Marcellus Shale-related construction, Penn State’s study has shown that invasive plants are spreading across many well pads.”

Invasive plants can grow and spread across sites quickly and displace native vegetation, Sitch said. In those areas, plant diversity is often reduced to one or two species. The ecosystem services provided by the once diverse collection of plants is lost, which creates a ripple effect for all other species in the forest habitat, he said.

Over the past decade, Barlow said the threat that fracking poses to an area’s water system has been well-covered, but as more research about the unintended consequences of natural gas extraction is published, a full understanding of the process is possible.

“It’s of course important to understand the impact on our water, but there’s been less emphasis on plant communities with this development,” Barlow said. “If plants are the foundation for what creates a habitat, I think the full story needs to be told.”

Tree of Heaven spreading wildly