Pro-B: A Practical Management Tool for Implementing Selection Silviculture

Pro-B, a method developed by U.S. Forest Service research, helps make uneven-aged management of longleaf pine and other forest types a practical and efficient option for landowners and managers. A field study by researchers showed that after less than three hours of training on the Pro-B (proportional basal area) method, managers were able to accurately mark stands using only a single marking pass.

Dale Brockway, research ecologist with the Forest Service Southern Research Station (SRS) Longleaf Pine Restoration and Management unit, worked with SRS emeritus scientist Ken Outcalt and Auburn University’s Ed Loewenstein (formerly of the Forest Service Northern Research Station) to create a technique that managers can easily use to apply uneven-aged management in the forest. Pro-B may be used to implement selection silviculture in a variety of forest types in the Southeast, elsewhere in North America, and perhaps on other continents as well.

Uneven-aged management (single-tree selection and group selection) is sometimes considered the more “natural” way to manage forests and involves selecting trees to harvest based on values such as protecting native plant communities, maintaining continuous forest canopy cover through time, and facilitating the development of large, old trees while providing a reliable supply of quality timber products.

“In the past, longleaf pine was mostly managed with even-aged methods such as shelterwood, and even thought to be too intolerant for uneven-aged silviculture, though recent evidence suggests that it’s a viable alternative,” said Brockway. “Even-aged methods were better developed than uneven-aged approaches, and earlier uneven-aged methods seemed to be too complicated and constraining for longleaf pine management.”

The researchers developed a method based on basal area, the cross-sectional area at breast height (4.5 feet) of all trees summed per unit area within a stand. Pro-B apportions stand basal area into a 1:2:3 ratio among three broad tree diameter classes, combining smaller diameter classes into three ecological and product-relevant categories. This requires tree markers to remember only three fractions as they mark the fraction of trees that should be removed in each broad diameter class.

The researchers conducted a study on two longleaf pine site types (flatwoods and uplands) in 18 stands on the Florida Coastal Plain to examine the effects of applying Pro-B on pine regeneration, stand development, and volume growth while observing how easily the method could be learned by managers from a range of professional backgrounds.

Results from two training workshops, which included field applications where managers marked trees to be harvested, confirmed the ease of learning and using the Pro-B method, and preliminary findings about its treatment effects are promising.

“Early results show that using Pro-B, managers achieved the target residual basal area with a high level of precision,” said Brockway. “Although our results suggest that Pro-B is an effective method for applying uneven-aged management to longleaf pine stands, one or more cutting cycles will be needed before its regeneration success can be more fully evaluated.”

Pro-B allows managers to retain large trees that enhance structural diversity and improve wildlife habitat, and to leave trees with abundant seeds or good form while removing less desirable trees and adjusting the spacing among retained trees. Pro-B provides guidance for thinning toward a stable stand structure while allowing for periodic removal of high quality forest products on a 10 to 15-year cutting cycle.

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

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