Proportional basal area method for implementing selection silviculture systems in longleaf pine forests
Proportional basal area (Pro-B) was developed as an accurate, easy-to-use method for making uneven-aged silviculture a practical management option. Following less than 3 h of training, forest staff from a range of professional backgrounds used Pro-B in an operational-scale field study to apply single-tree selection and group selection systems in longleaf pine (Pinus palustris Mill.) stands. Field crews achieved precision levels often within 3%–5% of the 11.5 m2·ha−1 target residual basal area. By aggregating many diameter classes into only three diameter-class groups, Pro-B improves efficiency by requiring tree markers to remember only three fractions, while making a single pass through the stand. Trees of large size, specific species and with good form, broad crowns and cavities can be retained, while adjusting spacing to release residuals. Systematic quantification of marking trees for removal enables different individuals to obtain similar results. Early observations revealed encouraging levels of pine regeneration and stand development, along with continuing good volume growth rates of 3% per year. Although less certain until one or more cutting cycles are completed, these early tests indicate that a stable mature forest structure should develop, which is characterized by the presence of large trees and natural regeneration.