Future Longleaf Pine Forests in Virginia

Longleaf pine cones. Photo by U.S. Forest Service, courtesy of Bugwood.org.

Southeastern Virginia marks the northern boundary of the natural range of longleaf pine forests, which once stretched along most of the Atlantic and Gulf Coastal Plains from Virginia to eastern Texas. Research aimed at finding the best seed sources to restore longleaf pine forests to southeastern Virginia area is also providing important clues for adapting forest ecosystems to changing climate.

When Captain John Smith landed in Jamestown in 1607, longleaf pine forests covered well over a million acres in southeastern Virginia. By the early 1800s, almost all of those forests were gone. Today, with the help of U.S. Forest Service genetics research, the Virginia Department of Forestry (VDOF) is working with partners to restore longleaf pine to the northern edge of its former range.

In 2005, only a few thousand longleaf pine trees still stood in Virginia, with less than 500 of those know to be genetically native. The VDOF started producing seedlings from native seeds, at the same time beginning research to evaluate whether, in light of the scarcity of native material and changing climate, they should also use seed sources from other parts of the species range.

In 2006, VDOF established longleaf pine provenance tests on three sites near New Kent, Virginia, in the northernmost part of the species native range. Provenance tests, long used to test the viability of seed sources, also provide a way to look at climate effects on trees from other areas. For these tests, seed came from a seed orchard in North Carolina and natural stands in North Carolina, South Carolina, Georgia, Florida, Alabama, and Mississippi.

In addition to the basic growth data collected  by the VDOF, researchers from the Forest Service Southern Research Station (SRS) Forest Genetics and Ecosystems Biology unit have been collecting data on the physiological processes of the test trees in relation to seed source.

“The original purpose was to find out if stock from nearby North Carolina could perform as well as native stock in Virginia, since there were so few trees native to Virginia left,” says Kurt Johnsen, SRS plant physiologist who leads the project. “We soon realized that this also gives us the ability to test the viability of stock from more southern sources. An interesting question is if more southerly seed sources can be planted in Virginia now to ‘pre-adapt’ them in case of climate change.” 

Longleaf pine seedlings in the “grass” stage. Photo by Ricky Layton, courtesy of Bugwood.org.

At the end of the fifth growing season on the test sites, SRS researchers assessed water use efficiency in relation to molecular genetic profiles of longleaf pine trees on all sites and from all sources. They found water use efficiency greatest in the Virginia trees, which also had the greatest growth on all three sites until the fifth year, when trees from other provenances caught up on two salubrious former nursery sites. Virginia sources still had the advantage on the third site planted on a clearcut with poorer soils and that experiences higher stress. Seven year growth will be measured shortly.

“Longleaf pine trees live from 60 to 200 years, so this data can only be seen as preliminary,” says Johnsen. The results indicate that Virginia seed sources are the most adapted to the region, but they also show that more southern sources adapt well to the northern climate. In the context of climate change, it may well be prudent for managers to incorporate some southern seed-derived seeds when restoring longleaf pine at the northern edge of its range.”

For more information, email Kurt Johnsen at kjohnsen@fs.fed.us .

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