Evaluating the Climate Adaptability of White Oak Trees on the Green Mountain National Forest

Photo Credit

USDA Forest Service photo by John Butnor

Leaves of a white oak seedling damaged in a springtime freeze.

White oak (Quercus alba) is found throughout forests in the eastern United States and is important for forest biodiversity. Its acorns are a key food source for wildlife and its strong, rot-resistant wood is valuable for making furniture, cabinets, flooring, and whiskey barrels. However, threats like invasive plants, pests, and climate change are putting the long-term survival of this vital tree species and its habitat at risk. This has raised concerns about the regeneration of oak seedlings and saplings in existing forests, the re-establishment of oaks in forest stands where they have been harvested, and the future availability of high-quality oak wood.

In 2023, scientists established a white oak common garden on the Green Mountain National Forest (GMNF) in East Dorset, Vermont. Common garden experiments involve planting species or populations of plants from different places together in the same environment. These experiments help scientists study various questions and theories by observing how the plants grow under the same conditions.

This project is a collaboration with the White Oak Genetics and Tree Improvement Project at the University of Kentucky.

Key Findings

• A springtime freeze event hit the region on May 18, 2023 (one month after seedlings were planted) and caused significant leaf damage to all newly leafed-out seedlings. Despite this, the affected seedlings recovered and grew even taller than those that had not leafed out yet and were not affected by the cold. This may be because white oaks have a cluster of buds rather than a single terminal bud like other species. These additional buds may offer ready “replacements” for leaves damaged in isolated freeze events.
• In 2024, the survival rate of the common garden seedlings was excellent, ranging from 88% to 100%, depending on the family.
• In spring 2024, the research team noticed that seedlings from northern areas of the country were further along in their leaf development compared to those from warmer, southern areas. This early leaf development may make them vulnerable to freeze events.
• The average height of seedlings from different families when planted in Vermont in April 2023 was linked to how well they germinated at the Kentucky state nursery. Factors like pollen availability, genetic diversity, and environmental conditions during flowering can affect acorn quality and germination. Families with higher germination rates produced taller seedlings.
• Seedlings from northern latitudes tended to be taller at planting but this trend leveled off by the end of the growing season.

Photo Credit

USDA Forest Service photo by Paula Murakami

The white oak common garden on the Green Mountain National Forest.

The research team planted seedlings from 44 half-sib families in 20 replicates in the common garden. Scientists are monitoring their growth, leaf development in spring and fall, and other aspects of leaf health. In winter 2024-2025, the research team will also assess the seedlings’ cold tolerance using differential thermal analysis.

The seedlings represent a significant portion of white oak’s natural growing range and are roughly grouped into eastern (from North Carolina to Vermont) and western (from Ohio to Minnesota) regions for analysis. Additionally, acorns collected from Vermont, New Hampshire, Massachusetts, and New York in fall 2023 were planted at the New York State tree nursery. The resulting seedlings will be added to the common garden in 2025.

Expected Outcomes

The aim of this project is to evaluate traits that help white oaks adapt to climate change, test their suitability in different locations, identify the best-performing trees, and guide restoration and assisted migration strategies for the species.