Longleaf Pine Silviculture

Selection Systems and Shelterwood Methods

By best estimate, longleaf pine forests once spanned over 90 million acres – an area more than twice the size of Georgia. “Today, 97 percent of these forests are gone,” says U.S. Forest Service research ecologist Dale Brockway. “However, the longleaf pine ecosystems that remain are home to a very diverse community of plants and animals.”

Longleaf pine ecosystems are home to many threatened and endangered species, such as the red-cockaded woodpecker. Photo by Mary Snieckus, USDA.

Longleaf pine ecosystems provide a host of ecological, economic, and social benefits, and many private landowners and public land managers want to restore the species. Currently, managers often use even-aged silvicultural methods. Even-aged methods result in stands where all the trees are roughly the same age and size.

However, there is growing interest in using uneven-aged methods. Uneven-aged silviculture results in stands where there is a range of tree ages and sizes, from small seedlings to growing saplings to adults that dominate the canopy. In uneven-aged stands, forest regeneration is almost always occurring, while in even-aged stands, it usually occurs after harvests.

“An extensive body of research exists about even-aged methods for longleaf pine, such as shelterwood with natural regeneration or clearcutting followed by planting nursery-grown seedlings,” says Brockway. “Uneven-aged silviculture, using single-tree selection or group selection, has received less attention, but our recent study shows it to be a viable management option for longleaf pine.” Brockway led the study which was published in the journal Forest Ecology and Management.

“Uneven-aged methods may help forest managers achieve a broader range of stewardship goals,” says Brockway. “These methods mimic natural regeneration patterns and small-scale natural disturbance regimes and can help create and maintain high-quality wildlife habitat, as well as provide many other ecosystem services.”

Single-tree selection results in stands where there is more space between individual trees, as the stand in the center of the photo shows. Photo by Bobby Cahal, Florida Forest Service.

Brockway and his coauthor Kenneth Outcalt – an SRS research ecologist who is now retired – compared the effects of even-aged and uneven-aged silvicultural techniques on two Florida forests, in partnership with the Florida Forest Service. Brockway and Outcalt tested two uneven-aged techniques – single-tree selection and group selection.

“Group selection closely mimics the natural regeneration process observed in longleaf pine ecosystems,” says Brockway. Group selection removes trees from a small area – anywhere between a quarter acre and two acres – to create gaps in the canopy, where longleaf pine seedlings can germinate and develop.

Instead of cutting groups of trees, single-tree selection removes individual trees throughout an entire stand. Single-tree selection harvests many sizes of tree – from small pulpwood sizes through larger sawtimber sizes. Single-tree selection creates very small canopy gaps.

“We found that single-tree selection produced less overall change in the forest ecosystem than group selection, which caused less alteration than shelterwood treatment,” says Brockway. “Single-tree selection appears to be an effective way to obtain natural regeneration in a stand.”

Longleaf pine can survive and thrive in a wide variety of habitats – mountains, dry sandhills, mesic uplands, flatwoods, savannas and swamps. Because of the incredible adaptability and wide range of this tree species, management decisions must be tailored to the habitat conditions and specific goals for each forest location.

“Long-term observation will be required to verify that selection can sustain forest ecosystems on sites characterized by differing environments,” says Brockway. “However, selection silviculture is perhaps the most cautious and seems to be a lower risk approach for guiding forests along a trajectory of gradual improvement through time.”

Read the full text of the article.

For more information, email Dale Brockway at dbrockway@fs.fed.us.

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