White Oak Regeneration in Canopy Gaps

Femelschlag study update

Clark and Scott Schlarbaum, UT-TIP Director, sort white oak seedlings into quality grades for planting. Poor quality seedlings are discarded. USFS photo.

In February 2020, USDA Forest Service scientist Stacy Clark planted 720 white oak (Quercus alba) seedlings on the Pisgah National Forest in western North Carolina.

“White oak is declining in abundance across the eastern U.S., and we are concerned that wildlife species and industries around cooperages, distilleries, and flooring will be negatively affected without proactive forest management,” says Clark. “We established this study to provide landowners with practical options for maintaining white oak trees in their forests.”

This planting is part of a larger, long-term study established in 2014 by Tara Keyser, research forester and project leader for the SRS Upland Hardwood Ecology and Management unit.

Keyser is researching how a silviculture practice called femelschlag promotes the regeneration of oaks. The practice is an irregular shelterwood system that creates an opening, or gap, in the canopy. Oak species are less tolerant of shade and are able to develop into the overstory of the canopy with more sunlight.

“This broad-scale manipulative study presents a unique opportunity to examine how silvicultural practices affect a wide array of ecological attributes that contribute to ecological complexity at a variety of spatial scales – in the gaps, at the stand level, and across the landscape,” says Keyser.

Her study is examining how gap-based silviculture affects ecological complexity, including natural tree regeneration, carbon dynamics, pollinators, herbaceous communities, and wildlife. Research partners include the Northern Research Station, North Carolina State University, Auburn University, and National Forests in North Carolina.

The survival of a planted white oak seedling is dependent on its root system. Photo by Stacy Clark, USFS.

Clark’s new planting provides an additional research component to the existing multi-faceted study. The Pisgah National Forest and the University of Tennessee’s Tree Improvement Program (UT-TIP) are cooperating on the study.

She will examine how seedling survival, growth, and competitive ability varies with location in and around the canopy gaps. Six half-acre canopy gaps were created through commercial timber harvesting on the study site in 2019.

UT-TIP collected acorns from mature oak trees in the region, which were grown for one year in a commercial tree nursery. The seedlings were then measured for height and root characteristics, tagged, and sorted into an experimental design for planting.

Researchers from Keyser and Clark’s research unit planted the seedlings with help from their partners on the national forest and with UT-TIP. They planted seedlings directly in the middle of a gap, along north and south aspects on the edges of the gaps, and a few meters outside of the gaps.

The gaps will be expanded in a few years to create a diversity of age and size structures that benefit tree species — including oaks — and wildlife species.

This study is one of the first of its kind to examine how an economically and ecologically important tree species like white oak can be regenerated artificially through planting in gap-based systems.

Forestry technician Jacquelyne Adams stands in the middle of a gap and plants seedlings in the 2 by 2 foot spacing treatment marked by pink flags. Photo by Stacy Clark, USFS.

“What makes this study unique is that genetic heritage is known for every seedling planted,” adds Clark. “Each seedling is highly characterized, so its size and root characteristics can be correlated later to survival and growth.”

The white oak study will provide information to managers and landowners who want to maintain or increase their oak component for future generations.

Research entomologist Bud Mayfield, in collaboration with Robert Jetton at NC State Camcore, also completed a recent planting of hemlock seedlings on the Pisgah. This study is evaluating how differences in sunlight levels across the femelschlag gaps affect eastern hemlock (Tsuga canadensis) and Carolina hemlock (Tsuga caroliniana) trees’ ability to fight off hemlock woolly adelgid infestations.

Recent and ongoing studies by Mayfield, Jetton, and research ecologist Chelcy Miniat suggest that the additional light from gaps created around hemlock trees may have both improved the trees’ growth and affected the size of adelgid populations.

The Femelschlag study was funded in part by a four-year NIFA-AFRI grant awarded in 2018. Tara Keyser and Jodi Forrester with North Carolina State University are its Principal Investigators.

Learn more about femelschlag and oak regeneration.

For more information, email Stacy Clark at stacy.l.clark@usda.gov.

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