A Race with the Red Queen

No disrespect to the ancients, but the best time to plant a tree was not 20 years ago. It might be this spring.

A variety of leaves from trees planted last fall in Highland Park. Photo by Taiji Nelson.

Whether plant, animal, virus, or bacteria, all living organisms are locked in battle with the pathogens, pests and parasites in their surrounding environment, using the tools and tricks nature’s equipped them with to keep them in the game. One of the strongest tools in this arsenal? The ability to adapt, to one-up opponents in a constant arms race.

One huge task that the Parks Conservancy faces is shoring up this arsenal for the trees in our care. The founders of these fine parks left quite the legacy, not only in the consideration that they gave to the design and experience of the parks, but also the impressive diversity of the urban forests.

It’s tough to overstate the importance of biodiversity to healthy parks. Voracious pests and sneaky diseases gain a slight foothold within the bounds of our parklands and spread like wildfire, faster than we can catch and quarantine them — even with sharp eyes out at all times. Our trees need their natural defenses as they stand on the front lines of these attacks, especially since they face added stresses of living in the city: polluted water, poor air quality, micro-climates, and human intervention.

London plane tree in Schenley Plaza.

A general in this battle, the Parks Conservancy’s Director of Park Management and Maintenance Phil Gruszka is a seasoned veteran. Phil has been rocking war paint for years now. Since conducting a study with Dr. Cynthia Morton of the Carnegie Museum of Natural History, he’s realized that our legacy park trees are impressive in their biodiversity… but that we have to really work to keep it that way. Their study found that tree stock from major nurseries across the country have actually been whittling down the tree gene pool.

“When London plane trees were first introduced to the United States, one nursery had a tree that did very well. But they couldn’t get it to reproduce from seed, so they started getting cuttings to grow out. Then they released it to the trade and named that cultivar ‘Bloodgood.'”

Selected for it’s superior resistance to the fungus anthracnose, the cultivar (a plant chosen for its particular genetic makeup) Bloodgood has been spread around now for about 30 years, dominating nursery stock of London planes. Plane trees bought from nurseries have identical genetic material to every other plane tree — they have not been grown from seed from two parent trees. They’re clones.

“Today, if I wanted to replace a London plane, I can only buy the cultivar Bloodgood.”

But trees from Schenley Plaza and around the park surprised them. “The Schenley Plaza trees were all genetically different, very diverse.” The park trees, planted before Bloodgood started to gain popularity, were much more diverse than the current nursery stock. The surviving 100, of the 200 that were planted years ago, were of a strong and diverse population, toughened from years of fighting off pests and disease.

Then, they widened their net. Was this true only for London planes? How much more diverse are our park trees than trees sold around the country? After polling nurseries from various parts of the country, they found that ten common trees used all over the U.S. were clones — their genetic diversity was actually getting less and less diverse.

Red oaks with oak wilt in Schenley Park, soon to be cleared.

Why has this study been so important? As the Parks Conservancy has taken on ecological restoration projects in the parks over the years and established the Park Tree Action Plan with the City of Pittsburgh, TreeVitalize, and Tree Pittsburgh, we’ve actively worked to increase biodiversity in the parks. Taking cuttings of our own heterogeneous tree stock, we’ve started growing new trees around the park and city in our own sort of diversity study, learning as we go about resistant new cuttings that withstand biological threats. This knowledge gives us only a peek at the immeasurable value of Pittsburgh’s parks; less mature forests and parks elsewhere are markedly more homogeneous, posing a threat to themselves and surrounding forests against the pests and diseases that have shown an uptick in recent years. Our trees are better equipped to keep our parks healthy and beautiful.

This week, a large stand of red oaks — about 50 trees in total — will be cleared from Prospect Drive in Schenley Park. Oak wilt, discovered earlier this year by an observant park user, got a stranglehold on the interlocking root system of the trees, infecting an entire grouping of trees. Left there, the trees are a risk to the health of other park trees. It’s terrible to have to take down so many trees, but it’s something that needs done for the overall well being of the park. And when these trees are replanted in the spring, a variety of new and diverse tree stock will be added to the expanding biodiversity and health of the park.

Wondering about the title of this post? Read more about the Red Queen Effect here.

Paints and Plants: What Ten High School Students See for Pittsburgh’s Future

The following post is from an area high school student, Lucy Newman, who worked with The Pittsburgh Parks Conservancy to lead a group of high school students in learning about the local environment.

Sketching out mural ideas

Last summer, I led a group of ten Pittsburgh high schoolers to paint a mural to answer an important question: What would Pittsburgh’s landscapes and communities look like if they were part of a healthy ecosystem?

The idea to paint a mural came to me while I was working at Sylvania Natives, a nursery that sells plants native to Pittsburgh. Kathy McGregor, the owner of the nursery, told me that I could create an internship project for myself. 

I like art, so I challenged myself to think of an artistic project about native plants. As I was walking home, I passed the five blank garage doors that are part of the nursery’s property. The idea struck me — I could paint them!

Two problems came to mind: it takes a long time to paint that much area (I’m a slow worker), and the cost of paint was too much for our small budget. I came up with the perfect solution to make this happen.

Why not turn this into a community effort and apply for a grant?

With lots of help from Kathy and Ms. Hetrick, my art teacher, the project evolved into a workshop. During the workshop, high school students learned about ecology and infrastructure and worked on designing the mural.

Sketching out mural ideas

“What would Pittsburgh’s landscapes and communities look like if they were part of a healthy, functioning ecosystem?” 

The question led the project. We talked to various environmental organizations, including The Pittsburgh Parks Conservancy, Tree Pittsburgh, the Clean River Campaign, Sierra Club Allegheny Group, and Sylvania Natives about our project. They gave us their take on the most important components of a healthy ecosystem. We discussed biodiversity, green infrastructure, and energy sources, among other topics. We assessed issues from multiple perspectives — the community, politics, and economic issues as well as the environment.

Pairing off to paint the mural

Next, we used these ideas to create sketches. We split off into pairs, with each pair tackling one of the five garage doors. Working together on this was really fun, and each group had a good deal of artistic talent. Talented local artists, like Silvija Singh, Karen Coyne, and Maria Harrington, also lent a hand. They helped us think about color, lines, unity and continuity. I was amazed that by the end of the second day each group had come up with great designs. Everyone had a unique take on the question, and was able portray their ideas in a way that looked awesome.

The last three days of the week, we painted. Supplies were donated through The Sprout Fund’s Hive Fund for Connected Learning. After outlining, we began filling in details, adding swirls of white in the blue water of a river, drawing veins onto leaves.

A week later, the mural was finished and we had all become great friends. And before we knew it, we were done! We had analyzed the question considering environmental, social, political, and economic aspects, and we had created a finished mural that depicted our answers. We had just designed a healthier, more sustainable future. And it was so fun, too!

Rock on, eco artists!

Life Goes Wherever Water Flows: Keeping Our Watersheds Healthy

Watersheds play an important part in maintaining healthy biodiversity in our local environment. Watersheds can carry sewage, pesticides and other harmful elements that can damage our ecosystem. What many people may not realize is that we all live in a watershed. Nine Mile Run and Panther Hollow are two examples of area watersheds the Pittsburgh Parks Conservancy are working to restore in partnership with the City of Pittsburgh and other area non-profits. Through the Carnegie Science Center’s “Take a Hike!” program sponsored by The Sprout Fund, our own director of education, Marijke Hecht, shows us what we can do in our own backyard to help keep area watersheds clean and thriving. For more information on the Nine Mile Run Watershed or Panther Hollow Watershed, visit our website www.pittsburghparks.org. To learn how you can get your own rain barrel to help divert extra water from the sewer systems, visit the Nine Mile Run Watershed Association website at www.ninemilerun.org.

Four Unsung Spots #3: Highland Park Seasonal Pools

What do you get when you cross a lawnmower with a huge, completely flat field of grass that just happens to be located at the foot of a very steep hill?

The lawn in February 2006

The lawn in February 2006

If you answered “a maintenance nightmare,” you’ll appreciate one of the Conservancy’s lesser-known capital projects, known as the Highland Park seasonal pools.  Once a large patch of grass that regularly flooded and contributed to water runoff onto Washington Boulevard near its intersection with Allegheny River Boulevard, this area is now a wetland habitat that’s unique in the Pittsburgh park system. 

Much like the Schenley pool meadow that we covered as our first unsung spot, the seasonal pools weren’t an original part of our Regional Parks Master Plan, instead arising out of a problem that more or less demanded a solution.  Several years ago, then-Mayor Tom Murphy commissioned a new trail in Highland Park to provide a link between the park and the rest of the citywide trail system.  The trail was originally slated to run across the lawn area, but the Parks Conservancy saw its construction as an opportunity to combat the woody invasive species that were aggressively taking over the bottom of the slope. 

The completed seasonal pools

The completed seasonal pools

So instead of creating a trail on a lawn that regularly flooded, the City’s Department of Public Works Construction Division routed the trail partially through the woods, creating a more unique experience for cyclists and hikers.  The team created basins, culverts, and outfalls so that the energy of the water coming down the hillside would dissipate, reducing flooding.  Along the south side of the trail, the seasonal pools (also called vernal ponds) were created to catch the water.  As Phil Gruszka, our Management and Maintenance Director, puts it, “That’s what that area wanted to be anyway,” but instead of being regularly mowed, now it could collect water and provide habitat.  In 2006, the trail and the pools were completed.

The Parks Conservancy began sowing native seed mixes all around the ponds, instantly laying the foundation for a biodiverse habitat.  Now instead of flooding a lawn full of grass whose roots aren’t deep enough to soak it up, the water goes into the wetland, filling the pools and infiltrating via the deep roots of dozens of different types of wildflowers.

Wildflowers spotted at the seasonal pools.  Top: Bloodroot, ironweed, and black-eyed susan.  Bottom: Blue vervain, buttercup, and butterfly weed.

Wildflowers spotted at the seasonal pools. Top: Bloodroot, ironweed, and black-eyed susan. Bottom: Blue vervain, buttercup, and butterfly weed.

The wildflowers are striking, especially this time of year when the black-eyed susans, ox-eyes, and bergamot create a sunny spectacle dotted with pale purple.  But what’s even more encouraging is the amount of animal species that have been spotted in this previously non-existent wetland habitat.  Some birds, such as the red-winged blackbird, prefer to live in wetlands, and there is a large colony of them that inhabits this space.  Dragonflies and damselflies buzz around the water, lighting on cattails.  Other species that have been spotted include great blue herons, snakes, slimy salamanders,  red tail hawks, and raccoons.  The pools have been a true success story in terms of bringing biodiversity into the parks.

Volunteers planting bald cypress trees

Volunteers planting bald cypress trees

They’ve been a success in other ways too, including as a site of community involvement.  In 2007 a group from the Girls Math and Science Partnership came out several times to do monitoring of water levels and quality.  We’ve had several cleanup events where we fished litter out of the pools that had run off the hillside.  And ecological restoration efforts on the site have been continual: the hillside had a number of invasive trees (mostly Norway maple) that have been removed, and new trees have been planted each season.  This spring we kicked off our Home Runs for Trees initiative by planting several bald cypress trees in the area between the pools and Washington Boulevard.  Now we’re focused on keeping all the new trees watered and healthy so that we can add biodiversity to the tree canopy in addition to the wetland.

So the next time you head over to the Washington Boulevard bike track to catch a race (or participate in one!), take a few extra steps and check out this relatively new habitat that’s bringing all kinds of new creatures into the park.   And don’t forget to bring your camera, just in case you spot a turkey hiding among the wildflowers!

(Wildflower ID thanks to this great site!)

The plants have really sprung up around the pools; heres the same view from April 2007 and July 2009.

The pools have really filled in; here's the same view from April 2007 and July 2009.

Nature by design

This is an article I originally drafted for Sylvan Communities magazine, but I thought I’d share it here as well.

It’s easy to forget when taking a walk through the lush woodlands in our regional parks that these natural wonders are actually designed landscapes.  When Frick, Highland, Riverview, and Schenley Parks were being developed from the late 19th to mid-20th centuries, teams of landscape architects worked to shape park users’ experience of nature.  Working largely in a traditional romantic picturesque style, they laid out parks with open meadows surrounded by woodlands that emphasized a rustic view of nature.  While there was certainly some vegetation in place when the parks opened, the selection of trees, shrubs, and herbaceous plants for the park was an important component of these designers’ work.

We can still see the efforts of these original craftsmen in places such as the Reynolds Street entrance to Frick Park, which contains open fields and planting beds leading into a series of forested trails.  Preserving these historic designs–and balancing them with the needs of today’s users–is a guiding principle of the Pittsburgh Parks Conservancy’s work with the City of Pittsburgh.  But along with history and modern use comes a third, and equally important element–ecology.

Stands of Japanese knotweed like this one in Highland Park grow quickly and are difficult to eradicate.

Stands of Japanese knotweed like this one in Highland Park grow quickly and are difficult to eradicate.

Today we have much more information about the ecological impact of the plants that are selected for the parks than the original designers had available to them.  The parks are collections of native and non-native species, many of which were imported from other areas of the world for their aesthetic beauty or their ability to grow well in this climate.  Over the years it became apparent that some of these non-native species were also environmentally invasive, and they began to have a devastating impact on the parks’ natural areas.  Trees such as Norway maple, Siberian elm, and tree of heaven, shrubs such as jetbead and privet, and herbs such as garlic mustard and Japanese knotweed have overtaken entire sections of parkland, killing or crowding out native species and vastly reducing the amount of biodiversity in the area.

The Parks Conservancy leads numerous volunteer projects aimed at educating the community about invasive species control.  Managing invasives is a major task of the Urban EcoStewards, volunteers who provide long-term care to designated areas of parkland.  Corporate and community volunteer days provide hands-on training to Pittsburghers of all ages, while putting thousands of hours annually into park maintenance.

In addition to combating invasive species, the Parks Conservancy is working to improve the long-term outlook for native plants.  The American chestnut tree made up almost 25% of Pennsylvania’s forests before the fungus that causes chestnut blight was imported in the late 1800s.  By 1950, the tree had been almost completely eradicated.  An extremely valuable source of food, habitat, and timber, the loss of the American chestnut was economically and ecologically devastating.  But foresters have hope that through backcross breeding techniques, new cultivars can be created from surviving American chestnut trees and the more blight-resistant Chinese chestnuts.  Pittsburgh’s Highland Park is home to an experimental orchard that is growing these hybrid trees.

Phil harvests chestnuts at the Highland Park orchard.

Phil harvests chestnut seeds at the Highland Park orchard.

The Highland Park orchard was planted in 1996 when the City of Pittsburgh, led by the support of then-City Forester Dale Vezzetti and then-City Councilman Dan Onorato, joined The American Chestnut Foundation‘s breeding program.  Blight-resistant Chinese chestnuts are pollinated with some of Pennsylvania’s surviving American chestnuts, with the ultimate goal of creating a tree with the characteristics of the American chestnut but the genes to resist blight.  Each year hundreds of seeds are generated, and these hybrid trees have been planted throughout the city parks, including test sites in Frick and Riverview Parks and in the Highland Park orchard.  The trees are studied over the years to determine how well the breeding process has worked, with a goal of using a new hybrid chestnut as a restoration planting when invasive trees are removed from a site.  The Parks Conservancy has been testing chestnut seeds in areas heavily populated by Norway maples to determine whether chestnuts can grow in soil that has been altered by the Norway maple.  The chestnut is an ideal restoration tree because it grows rapidly and can quickly re-establish a canopy, which in turn discourages the growth of sun-loving invasive species on the forest floor.

Another important park tree that fell victim to disease is the American elm, and the Conservancy is also part of efforts to reintroduce a hybrid elm that will be resistant to disease.  The Schenley Park Overlook is ringed by six hybrid elm varieties which are being studied by the Conservancy and the Penn State Cooperative Extension to determine their viability as landscape trees.  A crucial aspect of the study is whether these trees, which are bred partially from the invasive Siberian, Chinese, and other elm varieties, will become invasive in the surrounding woodlands.  The mulch beds around the trees are carefully observed for seedlings, and the forests (which contain no other elms) are watched to determine whether new trees are becoming aggressive and require action.  So far, the trees are not exhibiting aggressive tendencies and are functioning as positive replacements to the Norway maples that used to occupy the site.

Despite the many benefits of genetically diverse tree populations, modern horticulture is actually trending toward less genetic diversity in tree propagation.  New tree stock is often replicated from tissue culturing and cuttings, which can result in thousands of trees with the exact genetic makeup of a single parent tree.  Hybridization and sexual reproduction, by contrast, produce trees with diverse genetic makeup, reducing a tree population’s susceptibility to catastrophic loss.

The London Plane trees at Schenley Plaza have defined the space for almost a century.

The London Plane trees at Schenley Plaza have defined the space for almost a century.

In 2004, the Conservancy’s Director of Parks Management and Maintenance, Phil Gruszka, began working with Dr. Cynthia Morton of the Carnegie Museum of Natural History to study the genetic makeup of 81-year-old London Plane trees at Schenley Plaza.  Almost half of the original London Plane population at the Plaza had been lost to disease, and the Conservancy wanted to replant a new, genetically diverse group of London Planes as part of the Plaza’s 2006 restoration.  The study revealed that the remaining trees were very genetically diverse, providing an excellent alternative to the “Bloodgood” cultivar (which was originally taken from a single-parent cutting) that is most often raised and sold by nurseries.  Local nurseries began propagating new trees from the diverse population at Schenley Plaza, reducing the possibility that these new trees could infect each other should some of them contract a disease.  Schenley Plaza’s London Plane trees now represent a genetically diverse, historically inspired population.

The people of Pittsburgh owe a great debt to the original park designers, whose vision of beautiful natural retreats still enriches our lives today.  But the parks are more than attractive places to enjoy a stroll–they are ecological treasure troves, and maintaining them requires extensive knowledge and effort.  The Pittsburgh Parks Conservancy is proud to carry on the parks’ legacy and continue improving their ecological health for future generations of park users.