This post was originally published on April 25th, 2014. We’re republishing it today because it’s Arbor Day! Get out there and hug a tree, but first, read about someone who’s doing some awesome work to help save the American Chestnuts.
As we mentioned on Monday, today we’re introducing a new column called In the Field, where we tag along with someone doing interesting work. In this post we’re talking to Sara Lingenfelter (formerly Fitzsimmons), the regional science coordinator for the Pennsylvania Chapter of The American Chestnut Foundation (TACF). I think I can speak for both Sarah (my sister) and myself when saying that having an excuse to search out and talk to someone like Sara is just the sort of reason why we started Seasoned. I couldn’t wait to learn more about TACF’s mission and current projects as well as Sara’s research and the day-to-day aspects of her job!
Given that today is Seasoned’s first Arbor Day, we couldn’t think of a better tree to talk about than the American chestnut, Castanea dentata. Depending upon your age, you may have heard your parents, grandparents, and/or great-grandparents talk about the majesty of the American chestnut. These trees are native to the forests of the Eastern US, where they were considered extremely important for their role within the ecosystem and as a valuable economic resource.
Unfortunately, the tree’s population has been decimated by an invasive fungus, Cryphonectria parasitic, that was transported to the US in the early 1900s on a species of Asian chestnut. It was, and still is, common to import exotic species of plants to the US for use in home gardens and landscaping. The Asian trees were resistant to the fungus, while the American variety has no resistance to the fast-moving fungus, and by the mid-1900s, it is believed that over 3 billion trees were infected and eventually died. If this isn’t a reason to landscape with native species, we don’t know what is!
It is believed that 25% of the hardwood trees within the Appalachian mountains were once American chestnuts. These trees flower in the late spring or early summer, protecting their nut supply from frosts that would damage the flowers. By autumn, the mature nuts provide a reliable source of nutrition for many birds and mammals within the ecosystem at a time of year when the animals are building up their energy reserves for winter. Without this consistent supply, the ecosystems are now dependent upon mature oaks whose with an average nut production that is lower than the chestnut’s and that yo-yos from years with almost no yield to years of overabundance.
As an economic resource, the trees are valued for both their lumber and nuts. The value of nuts goes without saying. Chestnuts roasting over an open fire? Nothing better, but unfortunately you probably haven’t tasted an American chestnut, as today many of the roasted nuts you eat are from a European variety of the tree. The trees are the ideal lumber source because they are a fast-growing hardwood with a straight trunk. Additionally, the wood is rich in tannins, making it resistant to decay and maintaining its value as a reclaimed lumber long past its original use. Fun fact : Sara’s childhood home is paneled in American chestnut that her grandfather collected from a school-house that was being torn down. Numerous national and state park structures built by the Civilian Conservation Corp used American chestnuts.
Fortunately for us, there are a few remaining stands and a scattering of individual trees. Many scientists consider the species to be “effectively extinct” because the trees in their native range are too far apart to cross-pollinate, or are sprouts that will never reach maturity before succumbing to the fungus. I know what you’re thinking: without mature trees producing nuts, where are the sprouts coming from, right? Perhaps surprisingly, the blight that kills a mature tree, does not kill its root system. Sprouts are able to grow out of the remaining stump and root system but will become infected by the fungus before becoming mature enough to produce nuts.
There are smaller stands of the trees in their native range, including one in Ohio and another in Pennsylvania, but the largest and possibly most famous stand of American chestnuts is located in Wisconsin. Planted in the late 1800s, it is believed that this stand escaped the blight for over 80 years because they were outside of the tree’s native range, and there was no easy way for the fungus to travel from the forests in the eastern US to the forests of Wisconsin. Unfortunately, blight was discovered in the Wisconsin stand in 1987. Biologists and pathologists have been working to protect the trees ever since. In addition to that work, there are groups scientists and organizations like TACF working to develop a line of American chestnut that is resistant to the fungus with the hopes to successfully re-establish the species.
Founded in 1983, TACF’s mission is to breed a line of American chestnuts that are resistant to the blight while preserving the “genetic heritage” of the species. (I’m going to drastically oversimplify the process here, but you can read more about it by clicking on the links throughout this text.)
TACF uses a what they refer to as The Backcross Method, where they breed American chestnut trees with the resistant Asian variety. This produces a tree that is 50% American chestnut and 50% Asian chestnut. For the next three generations, they seedlings are “back-crossed” with pure American chestnuts to create a tree with 15/16, or about 94%, of its genetic material from the American tree. From there, they “intercross” the trees that are 15/16 American chestnut for two more generations. This link contains a helpful graphic of the breeding process. With each cross-pollination, the resulting seeds are planted, and the seedlings are inoculated with the fungus. Those that show no vulnerability to the fungus are selected for future breeding. The Foundation is now at the stage where they are planting resistant trees in their native range and monitoring their success!
Another extremely important component of their work is preserving the genetic diversity of the species and the blight resistant genes. With a native range as large as that once occupied by the American chestnut, the success of the species is dependent upon a population of trees that can live across a range of temperatures, precipitation regimes, soil types, and elevations. TACF increases the genetic diversity of their breeding program by adding new American trees to the program; at this time they have incorporated over 500 American chestnuts to their breeding line. It is possible for the fungus to evolve to overcome the trees’ new resistance, but this will be more difficult to do if there is variation in the genes coding for resistance against the fungus. To address this issue, the program has incorporated a number of Asian chestnuts that have shown particularly strong resistance to the fungus into the breeding program.
After learning about TACF and being excited about their mission, I couldn’t wait to talk to Sara. Approaching Sara’s office door, it was obvious that she’s someone who enjoys her job and is excited to share her passion. Our meeting was scheduled for 10am, and I walked into her office just in time to hear her bird clock chirp. Similar to the format of this post, I came to our meeting with a lot of information about the American chestnut and TACF’s work, and so I wanted to talk to Sara about some of the finer details of her days, her long-range plans, and the people actively involved with the foundation’s latest venture: planting late generation nuts and seedlings to repopulate their native range with blight-resistant trees.
This week alone, Sara was traveling to one planting near Pittsburg and then two days later heading to the other end of the state for a planting near Allentown. On the day I visited, Sara showed me the greenhouses with some of the seedlings that will be planted this year. I was so excited to hear about these large-scale plantings and asked about how they pick their sites. I had assumed that they were only planting in state forests, but learned that they have a range of sites from private farms and orchards to nature reserves and reclaimed strip mines. To date over 75,000 trees have been planted in PA alone. The sites donate their space for the planting, but just as important is that they provide volunteers capable of monitoring and caring for the trees. Sara is always fielding requests to plant resistant trees, and she said the biggest challenge to those requests is being able to determine if the person making the request has the long-range health of the trees in mind.
Of course, then there are the dream sites like the Milford Experimental Forest that have the support necessary to foster the trees and are tied to a rich history of forest conservation. This forest was established by James Pinchot, the father of Gifford Pinchot, founder and first chief of the U.S. Forest Service. Today members of the Pinchot family, including his great-granddaughter, Leila, carry on his work and are actively involved in the chestnut restoration plantings at the site.
Listening to her schedule, it’s obvious that Sara’s busy with plantings at this time of year, but I was still curious what a typical day was like for her, and I couldn’t have been more excited by her answer. Point blank: it varies by the season! As Sara is quick to point out, tree breeding is great for someone who likes to dabble in everything, from basic plant biology, to microbiology for culturing the fungus, understanding host-parasite interactions, and knowing statistics to be able to analyze the data. In the winter she’s busy going to meetings, presenting her work, doing data analysis and ecosystem modeling. In the spring she’s planting and distributing nuts for planting. That’s followed by tree selection and inoculating breeding trees with the fungus. By late spring and early summer they are pollinating the trees that have been selected for breeding. In late summer there’s a moment of rest, and then work picks up again in September and October when they harvest the year’s nuts. Then comes winter and the work starts all over again. How awesome is that? (Sarah here: I’ve picked the wrong profession. Abort life path, rewind, start over. I’m so jealous over here! What an intimate tree life Sara is living.)
As if that weren’t enough, Sara’s currently working towards her PhD, studying the few natural regenerating stands that exist to inform the planning and planting of future sites. The American chestnuts were lost when forestry and forest science was in its infancy, there’s very little known about the species and very little quantifiable data about the sites where the trees prospered in the forest; most of the information we have is from observational data.
When asked if she has an interest in expanding her research beyond chestnuts, she said she didn’t think she has “the bandwidth for another species”. Between the breeding work, and the planning and planting required to get the trees back into the woods Sara’s convinced that there’s enough work to keep everyone involved and busy for decades to come. I thought this was such an important point worth emphasizing. A good scientist can take a difficult problem, work towards solving it, and then explain the activities in such a way that it makes their work sound easy and it makes the problem sound like it’s been solved. Even in this post, I whittled down TACF’s work to a few simple paragraphs, making it sound much easier than it is, but there’s so much more to do. Sara, the other scientists, and the volunteers working for TACF will continue their breeding program, selecting trees with the highest resistance, trying to increase genetic diversity whenever possible, and introducing the trees into the forests, none of that work will end tomorrow. And what about the possibility of developing the American chestnut timber and lumber industry? That’s a dream to aim for in 100 years.
I asked Sara what she expects the PA forests to look like as these chestnut plantings mature. One thing is for sure, she doesn’t expect the chestnuts to re-establish the population they had before the blight, but given enough time, she does expect a healthy mix of chestnuts, oaks and beeches in the forest. As the chestnuts died off, they were replaced by oak and beech varieties. Knowing that the chestnuts are such a valuable food resource, Sara thinks that the ecosystems as a whole will do better with the chestnuts and the consistent nutrient resource they provide.
Wow. Do you want to get involved?
The first thing you can do is find the TACF chapter nearest you. The chapter websites have information about local plantings and volunteer opportunities. If you’re an educator, the foundation sells learning boxes with curricula for the classroom. Do you think you have an American chestnut near you? Collect a sample and send it in for proper identification. If it is a true American chestnut, collect the nuts and send them in for breeding! And finally, become a member of TACF! They still have a lot of important work to do.