In 1950, the US Forest Service initiated a cutting practice level (CPL) study on the Penobscot Experimental Forest in Maine on the basis of findings of a national appraisal of forestland management. Silvicultural treatments, including the selection system with 5- and 15-year cutting cycles, fixed diameter-limit cutting, and variants of commercial clearcutting, were chosen to represent "High-order," "Good," "Fair," and "Poor" cutting practices as then defined for eastern spruce–fir (Picea–Abies; northern conifer) forests. After 60 years, selection treatments have maintained a wide distribution of tree sizes, increased the proportion of mature spruce, and decreased the proportion of hardwoods; selection cutting on a 15-year cycle resulted in the highest current stand value. Fixed diameter-limit cutting resulted in the greatest harvest revenue but degraded residual stand composition, structure, and value. Outcomes of commercial clearcutting varied as a function of treatment (none, repeated harvest, or rehabilitation) after the first harvest. After 60 years, the proportion of acceptable growing stock was highest in selection and rehabilitation treatments and lowest in fixed diameter-limit and commercial clearcut treatments. Findings confirm that long-term outcomes of silvicultural treatments with attention to residual stand condition surpass those managed for short-term financial gains with regard to residual stand structure, value, and quality.
Rogers, Nicole; Kenefic, Laura; Crandall, Mindy; Seymour, Robert; Sendak, Paul. 2017. Sixty Years of Silviculture in a Northern Conifer Forest in Maine, USA. Forest Science. 64(1): 102-111. https://doi.org/10.5849/FS-2016-014.