Forest Plant Community Monitoring at Lincoln Boyhood National Memorial: 2011–2024

Light shining through the forest canopy at Lincoln Boyhood National Memorial, 2024.

NPS

Park Forests

Lincoln Boyhood National Memorial includes 200 acres of old fields and hardwood forest. Historical land surveys from 1805 show that the area was covered in oak-hickory woodlands, with a rich array of tree species including beech, black cherry, flowering dogwood, elm species, gum, shagbark hickory, ironwood, black locust, sugar maple, oak species, tuliptree, pawpaw, redbud, sassafras, sycamore, and black walnut.

When Abraham Lincoln's family settled here in 1816, they began clearing the land for farming. Much of the original forest was lost, with only small woodlots on the hilltop cemetery remaining intact. When the memorial was established, managers decided to restore the forest to provide visitors with a sense of what early settlers faced as they developed the land. Guided by the 1805 survey, nearly 40,000 trees and shrubs were planted.

Since the mid-1990s, the park has experienced a warmer and wetter climate. These warming temperatures may contribute to water stress for plants despite increasing rainfall. The Heartland Inventory and Monitoring Network monitors forest composition and structure to understand current condition of the forests and how they may be changing over time. This information helps parks evaluate how well their efforts are working to promote open woodland forests.

Monitoring the Forests

We have monitored forests at Lincoln Boyhood National Memorial since 2011. Four monitoring sites were established in the southern part of the park and sampled in 2011, 2015, 2019, and 2024. The sites represent a mix of successional hardwood forest and the old homesite restoration.

At each site, we collect detailed data on tree composition and structure. This includes identifying tree species, measuring diameter at breast height (DBH), and calculating basal area—a measure of how much area trees occupy based on the cross-sectional area of tree stems at breast height. We also record the number of seedlings and saplings, the tree status (live or dead), and evaluate canopy closure. For non-tree vegetation, we identify plants and estimate the percentage of ground area occupied by each plant species—a measure called plant cover, which helps track the abundance of plants over time.

A forest monitoring site at Lincoln Boyhood National Memorial

NPS

Forest Plants (2011–2024)

Trees

Forests on the park are dense with a closed canopy. Large trees—those exceeding 45 cm diameter at breast height—made up the greatest amount of tree basal area on monitoring sites. There were fewer overstory tree species in 2024 than in other years, although mean densities were similar. Management efforts to reduce invasive plants and promote a more open canopy will continue to be important for meeting park vegetation objectives.

Above average precipitation and a closed canopy have favored mesic tree species—those that require more water—over xeric trees species that are adapted to drier conditions. White ash trees continue to decline, which is expected with the persistent threat from the emerald ash borer. Although white ash seedlings and saplings are abundant, they remain highly vulnerable to infestation as they mature. The fast-growing tuliptree and more mesic sugar maple may benefit from the deep shade, increased moisture, and loss of ash trees.

Ground Layer

The ground layer of the forest is largely unvegetated and covered with shallow leaf litter. Ground flora species are not abundant, but plant cover was similar through time. Woody plants and forbs (non-woody, non-grass flowering plants) were the most abundant types in the limited ground flora. The shade-producing closed canopy and thick leaf litter are not ideal conditions for high ground flora diversity.

We observed 14 nonnative plant species since 2011 and 12 of these were present in 2024. The number of nonnative plant species has increased over time, but abundance of the two dominant nonnative species varied: Japanese honeysuckle declined while common periwinkle was greater in 2024 than in other years.

This homestead replica is typical of the 1820s. It is located on four of the original 160 acres owned by Thomas Lincoln, Abraham Lincoln's father.

NPS

Did You Know?

Restoring the oak-hickory woodland that was present when Abraham Lincoln’s family settled the area is a complex and ongoing challenge. Left undisturbed, these woodlands naturally undergo ecological succession, gradually becoming denser over time. As more trees fill in the gaps, less light penetrates the tree canopy. This allows more shade-tolerant trees to thrive. Over time, the woodland is transformed into a closed canopy forest.

Disturbances like fire can keep a woodland from progressing to a closed canopy forest. The park has implemented management actions to promote a more open canopy, including tree seedling plantings in 2018, 2019, 2022, and 2023; thinning trees; invasive plant treatments; and prescribed fire.

Despite these efforts, the forest at Lincoln Boyhood National Memorial has a closed canopy, with fewer herbaceous plant species growing on the forest floor. However, the forest that exists here today does meet the goal of providing visitors with a visual representation of the challenges the Lincoln family faced in clearing the forest and settling their homestead.

For More Information

View the Full Report. Visit the Heartland Inventory & Monitoring Network website.