Influence of Partial Cutting on Mountain Pine Beetle-Caused Tree Mortality in Black Hills Ponderosa Pine Stands; Forest Service research paper

摘要

Ponderosa pine stands were partially cut to various stocking levels at five locations, periodically surveyed, and remeasured during the 20 years after installation. Mean diameter generally increased 2 inches over the 20-year period on most partially cut plots and less than 2 inches on unmanaged controls. Average diameter growth for diameter classes in partially cut plots was generally significantly greater than average diameter growth for the same diameter classes in uncut control plots. Basal area increased 20 to 40 ft2/acre in partially cut plots and 5 to 21 ft2/acre in unmanaged controls at four locations over a 20-year period. Beetle-caused mortality ranged from 0 to 51 percent of the trees in partially cut plots and from 1 to 77 percent of the trees in control plots although mortality was generally less than 8 percent in partially cut plots. Beetles attacked trees ranging from 8 to 18 inches in partially cut stands and from 7 to 19 inches in unmanaged stands. Beetles did not exclusively attack greater than 16-inch diameter trees, so some trees greater than 16 inches may be selected as leave trees. However, if an infestation persisted in a stand, trees in diameter classes greater than 16 had the highest percentage mortality. The effectiveness of partial cutting for minimizing mountain pine beetle-caused mortality is influenced by: residual stocking level, size of the partial cut, amount of time since the area was cut, and proximity of beetle populations. Partial cuts of less than 10 acres may not minimize beetle-caused mortality if the cut stands are surrounded by unmanaged forest. Management to minimize beetle-caused mortality should be considered the top priority in mature ponderosa pine stands.