Partner Profile: Mapping Change - Monitoring Forest Dynamics

Marking a geographical point along the North Carolina/Tennessee boundary.

An NPS researcher marks a geographical point along the North Carolina/Tennessee boundary.

NPS photo.

It is a chilly morning. Bettina Uhlig, a researcher from Germany working for the National Park Service, pushes her way uphill through a tangle of trees, climbing on her hands and knees toward the blue sky glinting at the top of the ridge. When she arrives, she drops her bags, turns on her Geographical Positioning System (GPS), and breathes in the rich scent of forest growth and decay.

Why are we here? To answer, we need to go back 188 years. North Carolina became a state in 1789 and Tennessee in 1796, yet the boundary between the two was not decisively mapped until 1821, when William Davenport walked a line along the highest ridgetops in the Great Smoky Mountains. To mark his way, Davenport noted the species of “witness tree” at each milemarker and waypoint.

Topographical map showing Tennessee/North Carolina boundary.

Davenport marked the boundary between Tennessee and North Carolina, which the Appalachian Trail often follows through the National Park.

NPS map image.

Scientists conducting Inventory and Monitoring studies at the park knew that the written record of his route could lead to new research. They saw potential for a long-term monitoring study: Davenport had not only marked a state boundary, he had formed a 65-mile-long ecological transect (a line along which scientists take observations and samples) and documented the vegetation types existing in 1821 at regular intervals.

Bettina, who received her PhD in Geography comparing Chilean and Californian forests, came to the Great Smoky Mountains to work with scientists in the Inventory and Monitoring program. Before she left, she began a project to monitor the points along Davenport’s transect and compare the vegetation in 2008 to the vegetation in 1821. By doing so she hoped to record:

  • Species composition—which trees grow where, and with which other trees; are these the same communities Davenport noted? Bettina noted which species were dominant (existed in the highest numbers), co-dominant (shared habitat equally), occasional (perhaps not as well suited to the Appalachian ecosystem, but surviving), and rare (seldom found in the Appalachian mountains).
  • Forest health—does the forest consist of mature, healthy trees, or do only saplings remain? Davenport noted a large number of fir trees, which seemed to confirm past studies that indicated many, many more spruce-fir forests existed prior to European settlement. Many firs have fallen over the past decade due to Balsam Woolly Adelgid, a non-native insect from Europe, so Park biologists can use changes to monitor entire tree communities.
  • Shifts in ecological niches—have communities of birches, for example, moved to higher elevations over time? Do the beech gaps that Davenport recorded still exist amidst the spruce and fir?

Being able to compare—essentially to have a very long-term monitoring transect—is exciting because the park’s landscape has changed so much with logging and settlement, and will continue to change with climate shifts, air pollution, blights, and pests that have and are killing vast numbers of trees.

Leaf ID: Black gum, Chestnut oak, and Sugar maple.

Identifying species: Black gum, Chestnut oak, and Sugar maple at a site along Davenport's route.

NPS photo.

Before she leaves for the field, Bettina selects sites from Davenport’s route, which she’s charted on topographical map sections in the park’s Science and Education Center at Twin Creeks. She uploads topographical data into the GPS and packs this with a compass, plant guide, camera, paper and a pen, and plenty of snacks for the trail.

Often, the state line and the Appalachian Trail follow one another, so accessing Davenport’s “witness trees” is easier than it might otherwise be. In some sections, we hike for miles along the well-maintained trail and veer off for a quarter mile through thick forest. When we reach the site, she begins the site documentation: she notes the azimuth (compass direction) of the slope, marks the spot with the GPS so she can look at the route and points on a computer later, takes photos of the forest canopy and individual species, and then brings out the paper and pen.

Bettina notes every plant species that she finds within 50 meters of Davenport’s marked point. Ideally, she says, she would find a very old tree that perhaps had been marked with Davenport’s “X.” Even if she doesn’t, she checks to see if the species he noted are still growing at that point. Sometimes the forest is so dense that finding, identifying, and writing down all the species takes an hour or more. Other times, especially on high elevation ridgetops, there are only a few different species and she can record and move on to the next site quickly.

Dead firs from Balsam Woolly Adelgid near Clingmans Dome.

Changing landscapes: Balsam woolly adelgid (BWA) has killed firs all over the park, including these on a ridge near Clingmans Dome.

NPS photo.

After many attempts to find Davenport’s “X” marked witness trees, Bettina said that “even though we cannot hope to find very many old trees because they were farmed, or cleared, or fell victim to beetles and blights, the amazing thing is that the tree species Davenport noted still exist at the same points.” Early results contradict studies that said many more spruce-fir forests existed prior to European settlement.

The study has also recorded new data about Appalachian forests and how they change throughout the park. Bettina said she came here because it was an ideal place to study how tree species change their ecological niche (the conditions, including elevation, slope, soil type where they thrive) over different elevations. This is a good topic to investigate here because the mountains sit at the northern-most habitat range for many southern species, and the southern-most habitat range for many northern species, so we see many different trees coexisting and surviving in places they would not normally be found. For example the Sweet birch (Betula lenta) is a deciduous tree common in cold, moist Canadian ecosystems. In the Smoky Mountains, where temperatures are cool and precipitation high, the Sweet birch grows on ridges and north or south slopes—wherever there is space. At low elevations in the park, these trees are tied to shady riverbeds where it is wetter and cooler. We call the adjustments the birch makes to find its ideal home the Law of Relative Constancy of Habitat. This explains why it’s not contradictory for the birch to grow on exposed slopes at high elevation and only in deep, shady ravines at low elevation. We can see this Law at work all over the Great Smoky Mountains, where species adapt to varied habitats.

Rhododendron leaves curl to protect the plant from the cold atop Charlies Bunion.

Rhododendron varieties grow in specific ecological niches at the highest and lowest elevations in the park. This rhododendron curls its leaves to protect itself from the first cold snap.

Bettina hopes to find funding to return and finish her study next year, so that her species lists and photographs will be there to help future researchers study forest ecology along the transect and develop complete forest profiles. Bettina said that with this information scientists could compare habitat and ecological niches along the east and west sides of the park, and also on individual slopes. This would help managers in the park understand individual species better. It’s also vital that we know what’s there so we can protect it: this research provides another baseline documentation of the forest so we can monitor it as climate change, insects, invasive plants, and disease alter the landscape. Before Bettina left she reflected that “it may be impossible to see [these forest] changes in a lifetime, but the record [created] will exist for future scientists to monitor and compare forest ecology in the Smoky Mountains over time.”

Return to Dispatches from the Field: Issue 1 main page.

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