Archives For Julianne Beck

How Love and Science May Defend a Wild Orchid

Undercover Science

Julianne Beck —  February 18, 2016 — Leave a comment

Life on the prairie hasn’t been a breeze for the beautiful eastern prairie fringed orchid (Platanthera leucophaea).

Once common across the Midwest and Canada, the enchanting wildflower caught the attention of collectors and was overharvested throughout the 1900s. At the same time, large portions of its wet prairie, sedge meadow, and wetland habitat were converted to agriculture. By 1989, just 20 percent of the original population of Platanthera leucophaea remained, and the orchid was added to the federally threatened species list.

PHOTO: Claire Ellwanger takes a leaf sample in the field.

Claire Ellwanger takes a leaf sample in the field.

The struggles of the captivating orchid did not go unnoticed. Its lacey white flowers and unique biological attributes sparked a passion in scientists and volunteers across the Midwest who began gathering leaf samples for genetic analysis and recording measurements on the health of certain populations. Some volunteers dedicated decades to this work, and many continue to monitor their assigned location today.

As long ago as the mid 1800s, an earlier generation of the wildflower’s enthusiasts had preserved samples of actual plants, pressing them onto archival paper with their field notes and placing them in long-term storage facilities called herbaria, for future reference. As it turns out, some of the plant materials they saved are from populations that no longer exist.

Now, all of that data is coming together for the first time in a research study by graduate student Claire Ellwanger.

The master’s degree candidate—in a Plant Biology and Conservation graduate program run by the Chicago Botanic Garden and Northwestern University—is using modern analysis tools to uncover the genetic history of the species. What she finds will give scientists a better picture of the present-day status of genetic diversity of the species, and insight into the best ways to manage it for the future.

PHOTO: Clarie Ellwanger measures orchid seed pods in the field.

Claire Ellwanger measures orchid seed pods in the field.

“This orchid is a pretty interesting species because there has been this massive volunteer effort for over 20 years to restore it in Illinois,” noted Ellwanger, who said that Illinois currently houses more populations, or locations, of the species than any other state.

She is focused on collecting and analyzing genetic information on the remaining plants, working with field collectors in the Midwest from Iowa to Ohio, and also from Maine. She is examining the genes, or DNA, of each of the sampled populations, along with genetic information she collected at eight sites right here in Illinois.

Ellwanger is also extracting DNA from the older herbarium samples to better understand how much genetic diversity was a part of the species in the past. “The herbarium samples will allow us to get a sense of historic genetic variation to compare to levels today,” she explained.

Along with her thesis advisor, Garden molecular ecologist Jeremie Fant, Ph.D., she is especially interested in finding ways to maintain genetic diversity. “We know that if you are able to preserve the most genetic diversity in a species, it is more likely to persist for longer,” she explained.

PHOTO: Extracted DNA is ready for analysis in the laboratory.

Extracted DNA is ready for analysis in the laboratory.

In the lab today with her research assistant, Laura Steger, she uses a genetic fingerprinting technique on all groups in her study subjects. By watching the same sequence of genes over time and locations, she can see clear patterns and any changes. The bonus to it all is that “understanding more about these plants and their genetic variation will be pretty applicable to other species that have undergone the same processes,” she noted.

As scientists and volunteers worked in the field over the last several decades, they did more than collect genetic information. They also took steps to boost new seed production by hand pollinating plants or conducting a form of seed dispersal. Through her study, Ellwanger is also tracking the success of each technique. “I’ll be able to complete a genetic comparison over time to see if these recovery goals are achieving what they set out to do,” she said, by comparing the genetic composition of a given population from the recent past to today.

PHOTO: A compound light microscope reveals some plump, fertile embryos inside seeds

A compound light microscope reveals some plump, fertile embryos inside seeds.

At sites Ellwanger visited personally, she collected seeds as well, and brought them back to the lab for examination. There, looking under a compound light microscope, she checked to see what percentage of seed embryos from the sites were plump and therefore viable. Her findings offer an additional perspective on what her genetic analysis will show. After examination, the seeds were returned to their field location.

In early analysis results, “it looks like reproductive fitness does differ between sites so it will be really interesting to see if those sites that have lower reproductive fitness also have higher levels of inbreeding,” noted Ellwanger. Inbreeding, the mating of closely related individuals, can result in reduced biological fitness in the population of plants. In such cases, it could be helpful to bring in pollen or seed from other populations to minimize mating with close relatives and strengthen populations for future generations.

PHOTO: Eastern prairie fringed orchid (Platanthera leucophaea).

Eastern prairie fringed orchid (Platanthera leucophaea)

The eastern prairie fringed orchid will soon be better understood than ever before. The findings of the study may also provide insight into other problems that may be happening in the prairies where they live. “Orchids will be some of the first organisms to disappear once a habitat starts to be degraded. If we can better understand what’s going on with this plant it, could help out similar species,” said Ellwanger.

The researcher is looking forward to the impact this work could have on the future of the plant and the habitat that sustains it. “What motivates me about research is definitely the conservation implications,” said Ellwanger, who developed her love of conservation while growing up on the East Coast and learning about the complex systems that play a role in the health of the environment.

Read more about orchid research at the Garden, and don’t forget to visit the Orchid Show, open through March 13, 2016.


©2016 Chicago Botanic Garden and my.chicagobotanic.org

Water Works

Undercover Science

Julianne Beck —  January 2, 2016 — Leave a comment

In a first-time summer internship research project, two college students set out to understand how plants were responding to the Garden’s shoreline restoration projects. They took a deep look into how variations in water levels may be affecting the health of the young plants. The results of their work will help others select the best plants for their own shorelines.

A silent troop of more than one-half million native plants stand watch alongside 4½ miles of restored Chicago Botanic Garden lakeshore. The tightly knit group of 242 taxa inhibit erosion along the shoreline, provide habitat for aquatic plants and animals, and create a tranquil aesthetic for 60 acres of lakes.

PHOTO: The North Lake shoreline.

The North Lake shoreline restoration was completed in 2012. Photo by Bob Kirschner

Now ranging from 2 to 15 years old, the plants grow up from tiered shelves on the sloping shores. Species lowest on the slope are always standing in water. At the top of the slope, the opposite is true, with only floods or intense downpours bringing the lake level up to their elevation.

Wading In

Jannice Newson and Ben Girgenti moved through clusters of tightly knit foliage along the Garden shoreline from June through August, taking turns as map reader or measurement taker. On a tranquil summer day, one would step gingerly into the water, settling on a planting shelf, before lowering a 2-foot ruler into the water to take a depth measurement. The other, feet on dry land, would hold fast to an architectural map of the shoreline while calling out directions or making notes.

Newson, a Research Experiences for Undergraduates (REU) intern and sophomore at the University of Missouri, and Girgenti, a Garden intern and senior at Brown University, worked under the guidance of Bob Kirschner, the Garden’s director of restoration ecology and Woman’s Board curator of aquatics.

PHOTO: Interns Ben Girgenti and Jannice Newson.

Interns Ben Girgenti and Jannice Newson gather plant data on the shoreline.

When the summer began, Girgenti and Newson had hoped to locate and measure every single plant. But after the immense scope of the project became clear in their first weeks, they decided to focus on species that are most commonly used in shoreline rehabilitation, as that information would be most useful for others.

View the Garden’s current list of recommended plants for shoreline restoration.

“We’re interested in which plants do really badly and which do really well when they are experiencing different levels of flooding, with the overall idea of informing people who are designing detention basins,” explained Girgenti, who went on to say that data analysis of the Garden’s sophisticated shoreline development would be especially useful for others.

“The final utility of this research will be to inform other natural resource managers,” confirmed Kirschner, who added that successful Garden shoreline plants must be able to withstand water levels that can rise and fall by as many as 5 feet several times in one year.

Steering the Ship

Along the shoreline, the interns followed vertical iron posts that were installed as field markers during construction, in order to find specific plants shown on the maps. “The posts are pretty key to being able to map out the beds,” said Girgenti.

PHOTO: The Malott Japanese Garden shoreline 3 years after the 2011-12 restoration project.

The Malott Japanese Garden shoreline two years after the 2006 restoration project.

Once they found a target plant, they then counted clumps of it, and put it into one of six categories based on the amount of current coverage, ranging from nonexistent to area coverage of more than 95 percent.

They also measured the average depth of water for beds with plants below the water line, noting their elevation. For plants above the water line, the elevation was derived from the architectural drawings.

Data about the elevation and coverage level of each measured plant, together with daily lake water level readings dating back to the late 1990s, was then entered into a spreadsheet and prepared for analysis to identify correlations between planting bed elevation and plant survival.

Beneath the Surface

For her REU research project, Newson was careful to collect data for one species in particular, blue flag iris. “As a preliminary test of the project hypothesis, data relating to 101 planting beds of Iris virginica var. shrevei were analyzed to see if there was a significant correlation between the assessed plant condition and each planting bed’s elevation relative to normal water,” she explained in her final REU poster presentation in late August.

PHOTO: Southern blue flag iris.

Southern blue flag iris (Iris virginica var. shrevei), photo by Jannice Newson

An environmental science major, she initially experienced science at the Garden as a participant in the Science First Program, and then as a Science First assistant, before becoming an REU intern.

Girgenti began his Garden work in the soil lab, where his mentor inspired him to focus on local, native flora. “I was kind of pushed up a little bit by the Garden,” he said. The following year he did more field work in the Aquatics department. “I wanted to come back because I really enjoyed being here the last two years,” he said. “Every year I’ve come back to the Garden, I’ve been very excited about what I’m going to do.”

Aside from the scientific discovery, the two also refined their professional interests. “I do enjoy being out in the field as opposed to maybe working in a lab; it’s a lot more interesting to me. And also just working in the water with native plants is very interesting,” said Newson.

“I was really interested in getting into more of the shoreline science and also learning which native species were planted there,” said Girgenti. “I really love working here. I’ve never really been involved this much in science, so this has been a really great experience—just all of the problem solving that we’ve had to do over the course of the summer.”

Newson also enjoyed the communication aspect of her work, as Garden visitors stopped to ask what work she and Girgenti were doing along the shoreline. She was especially excited to share with them and her fellow REU interns that “the purpose of why we are doing this is that it provides a beautiful site for visitors to see, it helps with erosion, and also improves aquatic habitat.”

PHOTO: View of the Kleinman Familly Cove.

A view of the Kleinman Family Cove highlights the small bay where our youngest science explorers can learn about the shoreline.

Although the interns have left the Garden for now, the data they collected will have a lasting impact here and potentially elsewhere. Kirschner is currently working with his colleagues on the data analysis to complete a comprehensive set of recommendations for future use.


©2016 Chicago Botanic Garden and my.chicagobotanic.org

The Secret Society of Soil

Undercover Science

Julianne Beck —  December 21, 2015 — 4 Comments

When you lift a rock in your garden and glimpse earthworms and tiny insects hustling for cover, you’ve just encountered the celebrities of soil. We all know them on sight. The leggy, the skinny, the pale…the surprisingly fast.

Behind this fleeting moment are what may be considered the producers, editors, and set designers of the mysterious and complex world of soil—fungi. They often go unrecognized, simply because most of us can’t see them.

PHOTO: Otidea decomposer.

Otidea, a decomposer

Fortunately, new technologies are helping experts, like Chicago Botanic Garden scientist Louise Egerton-Warburton, Ph.D., get a better look at fungi than ever before, and discover vital information.

“One of the problems we have with soil science is that you can’t see into it so you really depend on a lot of techniques and methods to work out what’s happening,” explained Dr. Egerton-Warburton, associate conservation scientist in soil and microbial ecology. 

In the last year, she has used high-throughput sequencing (also termed Next Generation Sequencing) to identify more than 120 species of mycorrhizal fungi in a single plant community. In contrast, previous reports suggested there were, at most, about 55 mycorrhizal species in a plant community. These tiny heroes are microscopic organisms that attach themselves to plant roots, for example, to carry out critical functions that support all life on earth. They are essential for the well-being of more than 85 percent of all plants, including those in your garden.

Mycorrhizal fungi are fungi that have a symbiotic relationship with roots of a vascular plant; from the Greek for “fungus” and “root.”

PHOTO: White mushrooms.

Mushrooms are the above-ground fruiting body of fungi.

If climate change results in more intense rainfall and drought—as is predicted by climate change scientists—mycorrhizal fungi will also play an important role in processing varied levels of water in the soil.

Egerton-Warburton has just returned from November field work in the Yucatán peninsula of Mexico, where she has been testing the responses of mycorrhizal fungi to changes in rainfall and soil moisture, especially to drought. Will fungi be able to keep pace? Will they be able to survive? What does that mean for other plant life? “Fungi are really good indicators of any environmental problems. So they are more likely to show the effects of any environmental stress before the plants will,” she said.

Each type of fungi also has a specific role, according to Egerton-Warburton, with some specialized to take up nutrients from the soil, while others cooperate to complete a function, such as fully decomposing a leaf.  A lot of fungi are needed to keep the system working. “You get 110 yards of fungal material in every teaspoon of soil,” she explained.

Aside from breaking down deceased plant material, fungi play a key role in many plant-soil interactions and the redistribution of resources in an ecosystem. They filter water that runs into the ground, cleaning it before it hits the bottom aquifers and drains out into rivers. Also, in the top few inches of soil, many fungi are respiring, along with their earthworm and other living counterparts, helping to filter gases and air that move through the system. Of growing interest, is also the fact that fungi could have a major role in soil carbon sequestration.

Soil carbon sequestration is the process of transferring carbon dioxide from the atmosphere into the soil in a form that is not immediately reemitted.

PHOTO: Leucocoprinus fungi.

Leucocoprinus fungi

For the past four years, Egerton-Warburton and colleagues at Northwestern University have been working to better understand the flow of carbon through fungal communities that results in long-term soil carbon sequestration. Soil’s capacity to store carbon is a reason for hope and a potential way to mitigate climate change. According to Egerton-Warburton, soil is known to hold three times more carbon than plants and trees above ground. “Maybe there are other ways we can manage the systems and enhance that capacity in the soil,” she said.

The study has required a lot of ‘getting to know you’, as the researchers first sought to identify each type of fungi involved in the process of carbon sequestration. As plant parts above ground are faced with absorbing and converting larger and larger amounts of carbon dioxide from our atmosphere into sugars, and sending it down into their roots, the more beneficial it will be to have a healthy suite of fungi waiting to receive it, use it, and move it along for future long-term storage.

Part of this equation has been to understand which fungi benefit from the increasing supply of sugar. Previous work by Egerton-Warburton has shown that mycorrhizal fungi respond to increases in atmospheric carbon dioxide by producing large quantities of hyphae, a fine root-like structure, in the soil. This is because increases in atmospheric carbon dioxide allow a plant to produce more sugars during photosynthesis, and these sugars are shunted below ground for use by roots and their mycorrhizal fungi. At the other end of the equation are saprophytic and decomposer fungi, waiting to break down the new hyphae.

Recent work in the Dixon Prairie has used the high throughput sequencing and chemical fingerprinting to identify the fungi involved in this decomposition phase. Once that is resolved, they will be able to better understand how the fungi interact and balance the cycle carbon through specific pathways of activity.

Learn more about soil science in the winter 2015-16 issue of Keep Growing, pages 28-30.

PHOTO: Louise Egerton-Warburton.

Louise Egerton-Warburton at work in the soil lab

The more the merrier, when it comes to fungi, and when it comes to people who are willing to help them endure, said Egerton-Warburton. The scientist often works with students who are interested in careers in the field, but encourages additional people to consider this critical line of work. “There’s a real need for soil ecologists in the country,” she said.

The good news is that the future story of fungi is one we can all help to script. Gardeners, she advised, can pay attention to the type of mulch they use in their garden, and plant lots of native species that will naturally enrich the function of that wonderful world that holds us up.


©2015 Chicago Botanic Garden and my.chicagobotanic.org

Capturing the Value of Wild Plants

Undercover Science

Julianne Beck —  October 11, 2015 — 2 Comments

Maps had been followed, clues tracked, and early this summer the fortune was found.

Standing on the far side of a hummock swamp in Delhaas Woods in Bristol, Pennsylvania, Andrew Bunting had located a unique magnolia tree population on the edge of fading away. He had discovered the treasure he set out to find. Often, this is where the story ends. But when the prize is an elusive plant sought by scientists nationwide, this is where the story begins.

PHOTO: Andrew Bunting collecting sweet bay magnolia samples in Delhaas Woods, Bucks County, Pennsylvania.

Andrew Bunting collecting sweetbay magnolia samples in Delhaas Woods, Bucks County, Pennsylvania.

Bunting, the assistant director and director of plant collections at the Chicago Botanic Garden, was on day three of a nine-day adventure across the East Coast to collect northern populations of Magnolia virginiana var. virginiana L.

Bunting welcomes any opportunity to stroll the Garden campus. “I like all the Gardens, of course, but there are a few favorites,” he admitted. “Part of me likes horticulture and part of me likes the scientific evaluation side of things.” He often stops through the Heritage Garden with a nod to statue of Carolus Linnaeus and the Bernice E. Lavin Plant Evaluation Garden.

After locating a group of trees in Delhaas Woods, he and his team took cuttings from new growth and packed them into their bags. The murky waters that now stood between them and a successful exit from the overgrown site were deep and dangerous, and wading out was not an option. They had no choice but to leap between hummocks—floating islands—of knotted blueberry vines, wild roses, and other invasive plants to reach stable ground.

It’s all in a day’s work for Bunting, who has gone on wild plant-collecting trips around the country and world during his career. Days after returning home, he explained that this adventure was no more tame than those in tropical jungles. However, the importance of this collection made it all worthwhile. The target species, commonly called sweetbay magnolia, is generally underrepresented in living collections and arboreta. That means that if it is lost in the wild due to extreme weather or other threats, there is no backup. It could be gone for good.

PHOTO: A sweetbay magnolia tree stands out in Delhaas Woods, Bucks County, Pennsylvania.

A sweetbay magnolia tree stands out in Delhaas Woods, Bucks County, Pennsylvania.

By taking plant samples from the field, he and his team hope to grow new generations of sweetbay magnolia plants that can be safely maintained in secure locations long term and used to study and potentially boost the wild populations in the future.

The success of the trip required more than one stop. The team visited multiple locations, collecting from several plant populations across the northern range of the species. Their goal was to collect trees with novel traits, or genes, which would be beneficial for future breeding.

When the team navigated the swamp, their spirits were still high from an especially unique collection they made the day before in the Michaux State Forest, about 125 miles west of Philadelphia. There, they had carefully taken cuttings from a population of state-threatened magnolias that grows far from any other. “I’m hopeful that some of our work may lead to help figure out why that population is where it is,” remarked Bunting, who theorized that the population may have had a broader range millions of years ago and retracted to the coastal plain. He hopes that future DNA tests of the samples will provide answers by clarifying genetic similarities and differences between this and other populations they collected.

Moving into New Jersey, he and his team next gathered additional cuttings. Working closely with project partner Joe Rothleutner, tree and shrub breeder at the Morton Arboretum, and other local experts who joined them along the way, Bunting assembled a detailed logbook to accompany the physical samples.

PHOTO: Magnolia virginiana var. virginiana L. in Michaux State Forest, Pennsylvania.

Magnolia virginiana var. virginiana L. in Michaux State Forest, Pennsylvania.

At every collection location, each team member played a specific role to capture information about the site; from the type of soil to the slope of the land to a description of the local ecosystem, and a list of associated plants. At each site, two 10-inch plant samples, ideally with forming fruits and/or flowers, were pressed between cardboard and labeled for future storage in a herbarium. Other samples were packaged for propagation. The collection project was funded by the U.S. Forest Service and American Public Gardens Association (APGA).

The challenges along the way made every discovery that much sweeter. “What’s nice is you all kind of bring your own expertise and experiences and figure out how to navigate the areas and how to extricate yourself from the areas,” said Bunting. “What’s great about the collecting trips is that you can do a lot of front-end research but there are always surprises,” he added.

On the final leg of the journey, the team members found themselves wearing knee-high boots in the thigh-high waters of a sphagnum swamp in Staten Island. Sinking in deeper with every step, they waded through, only to find no evidence of magnolias. Swatting away mosquitoes and dodging deer ticks, they navigated a thick understory of sharp phragmites reeds and Japanese knotweed to make their escape.

PHOTO: An extended telescopic pole is used to take cuttings of the current season’s plant growth.

An extended telescopic pole is used to take cuttings of the current season’s plant growth.

In all, they returned home with representatives from nine populations and 850 unique cuttings.

Many of the species on display at the Garden today were once such wild treasures, explained Bunting, who, after years working for esteemed institutions across the country, returned to the Garden this spring in part to re-establish a collection program.

Records of wild collected plants’ origins hold a value that extends beyond dollars. Details of when and where each collected plant was gathered are stored in the Garden’s plant records database. Those pieces of information build a story for each specimen. The stories provide guidelines for conservation scientists who may need to propagate the species should a natural habitat be temporarily lost, and for breeders who may wish to develop a new, hardy species to better endure harsher winters, for example.

Many other species of plants are preserved when their seeds are collected and placed in seed banks. However, for some, such as the sweet bay magnolias, timing the seed collection and storing them long term is difficult, so the cuttings are the best approach.

Mapping the Journey

Bunting is building a ten-year collection plan that he expects will take Garden experts to one or two national and one international location(s) each year. “I would like this new plant-collecting program to really think about filling a lot of needs at the Garden, whether it’s evaluation, breeding, plant conservation, adding to our horticulture collection, or maybe interpretation and education,” he said. Collections will take place in similar climates to the Chicago area.

PHOTO: In Delhaas Woods, cuttings are labeled and pressed between pieces of cardboard for transportation to a herbarium for further processing and storage.

In Delhaas Woods, cuttings are labeled and pressed between pieces of cardboard for transportation to a herbarium for further processing and storage.

Plants selected for collection may be representative of a different country, or they may expand the Garden’s representation of a specific species, for example. Working with other Garden scientists, graduate students, and the Morton Arboretum, he is also building in steps to ensure that species are screened in advance so that no potentially invasive species are collected.

“There are lots of parameters and variables that will evolve over time and also partnerships,” he said. The collecting trips will be done with a consortium of institutions from across the country. Results will be shared and tracked among them, and stored at the herbarium at the U.S. National Arboretum in Washington, D.C. Many will also remain long term at the Garden or other similar institutions. “We do want to fill in gaps (in the Garden’s collection), but we also want to add diversity,” said Bunting.

Sweet bay magnolia trees in a New Jersey state forest

Sweetbay magnolia trees in a New Jersey state forest

Over the next several months, Rothleutner will work to propagate the recent sweetbay magnolia cuttings. They will then be dispersed among selected gardens, including several that together hold a full representation of magnolia species from the United States and that are coordinated by the APGA. Plants will also be cultivated at the Chicago Botanic Garden.


©2015 Chicago Botanic Garden and my.chicagobotanic.org

Embracing Trees for Our Future

Undercover Science

Julianne Beck —  July 13, 2015 — Leave a comment

If you spot a Chicago Botanic Garden volunteer wrapping their arms around a tree trunk this summer, don’t be surprised—what looks like a loving hug is actually a scientific measurement in process.

Using a specially designed tape measure, volunteers are recording the diameter of each tree before calculating the amount of carbon dioxide it stores. The study, launched by the Living Plant Documentation department five years ago, records the amount of the pervasive greenhouse gas stored by the Garden’s trees. The research team is interested in determining which trees are able to hold the most carbon for the longest amount of time.

PHOTO: Boyce Tankersley is researching the trees' response to increased carbon in the atmosphere, using data such as the growth rate of the particular tree species.

Boyce Tankersley and volunteers measure the diameter of each tree on the Garden campus.

The Tall and Short of It

It is one of the first such studies underway in a botanic garden setting. “We know carbon is increasing but we don’t have the numbers on how much carbon is being locked up by the urban forest,” said Boyce Tankersley, director of the Living Plant Documentation department. “This is where the Garden can play a role.”

Although similar studies have been completed by the lumber industry and others, it is important to understand how increased levels of carbon dioxide in the atmosphere are mitigated by cultivated trees, explained Tankersley. It’s also essential to document how those trees fare long term in evolving conditions.

The Garden has an especially diverse number of taxa, Tankersley said, positioning it perfectly to document how numerous species behave in locations from the McDonald Woods to the English Walled Garden to the parking lot. “The Garden is among the first to look at the trees in a Garden setting and at the diversity of taxa,” said Tankersley. “That’s a piece we’d like to shed more light on.”

This summer marks the second time the trees have been measured since the original data was gathered in the first year. Measurements will continue to be taken for another 15 to 20 years.

“We hope, when the data is analyzed, to be able to identify not only the trees that are best but the Garden settings that support their efforts in this regard,” anticipated Tankersley.

PHOTO: Tree canopy.

The Living Plant Documentation department is calculating the amount of carbon dioxide stored in each of the Garden’s trees.

Deep in the Woods

Trees are lauded for coming to our rescue in the face of climate change, but scientists have learned that these strapping heroes may not be infallible. “One thing we are looking for is the influence of carbon on the growth rate,” said Tankersley. His research team is paying close attention to the trees’ response to increased carbon levels in our atmosphere.

According to Tankersley, it has been documented that trees are growing more quickly than they have in the past, which comes with positive and negative repercussions. “Trees are providing an environmental service in a major way by absorbing carbon, but there’s a point of diminishing returns,” he explained. The wood of a fast-growing tree is softer, for example, which has a negative impact on the lumber industry, he explained. In addition, “with an increased growth rate, you also get increased susceptibility to insects and diseases.”

The concern underscores the need to observe the Garden’s trees for many years to take all such factors into consideration.

In addition, the team is watching the impact of weather on the trees, and taking dry spells or rainy periods, for example, into account when documenting tree growth over a given time frame. The Garden hosts a National Weather Service monitor on-site, which allows for weather-related calculations to be even more precise.

The Zipline

When the measurement phase of the study is complete, Tankersley plans to provide the data to a doctoral student in the Garden’s joint degree program with Northwestern University for formal analysis. “My take-home would be a list of the six best trees, perennials, and shrubs for sequestering carbon in the landscape in Chicago,” he said.

“We expect to find that trees like oaks, elms, and hickories—trees that are long-lived—provide a greater environmental service in this regard,” he added.

For homeowners who would like to assist with the issue now rather than wait for the final analysis, he suggests that they begin planting longer-lived trees. It may help mitigate, or reduce, the amount of carbon in the air and resulting climate change impacts such as extreme weather.

Our 2013 adaptive planting study carefully selected 60 suitable trees to plant for future generations. View the full list of suggested trees here.
PHOTO: Fastigiate English Oak acorns (Quercus robur).

It takes more than one year for the Garden volunteers to check the diameter of the 13,493 trees on-site, and enter the estimated carbon storage into a specialized database. The calculations are made using a formula developed by the U.S. Forest Service, said Tankersley.

The technique of measuring existing trees and planning for new plantings is something Tankersley hopes will have broad impact. He has already shared his process with countries in Africa through The Eden Projects and in China in an effort to help governments replace denuded forests there.

Tankersley is hopeful about the long-term implications of the study. After all, he said, when pioneers first came to the United States, they found oak trees that were about 300 years old, and had been providing benefits such as carbon sequestration for all of that time. Many of those hard-working, long-lived species have been a key part of our natural heritage since the beginning. By embracing the issue now, Tankersley and team have cleared the way for trees and their vital functions to endure.


©2015 Chicago Botanic Garden and my.chicagobotanic.org