The influence of partial cutting on mountain pine beetle-caused tree mortality in Black Hills ponderosa pine stands

Abstract

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 ft 2 /acre in partially cut plots and 5 to 21 ft 2 /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 <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 >16-inch diameter trees, so some trees >16 inches may be selected as leave trees. However, if an infestation persisted in a stand, trees in diameter classes >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 <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.

Multi‐temporal ecological analysis of Jeffrey pine beetle outbreak dynamics within the Lake Tahoe Basin

“…The positive relationship between JPB-attack and basal area grew progressively stronger through incipient and epidemic phases then waned during the post-epidemic portion of the outbreak. This relationship found within Jeffrey pine forest type is similar with those consistently found between bark beetle-caused mortality and stand density during outbreaks of MPB and western pine beetle (D. brevicomis) within ponderosa pine forest types (Oliver 1997;Cochran and Barrett 1998;Schmid et al 2007;Egan et al 2010). Dense forest stocking levels have been identified as beneficial habitat for a variety of bark beetle species as these characteristics promote tree competition for limited light and water resources and thus reduce individual tree vigor, while providing beneficial microclimate habitat that promote pheromone plume stability, shading to limit bark temperatures, reduced wind speeds, and other factors that have not received scientific evaluation to-date (Mitchell et al 1983;Coops et al 2006;Thistle et al 2011).…”

“…These results are mixed in comparison to studies of MPB outbreaks in respective ponderosa and lodgepole pine forest systems. For example, they are consistent with long-term studies within the Black Hills of South Dakota that indicated MPB-caused tree mortality initiated within small-diameter trees at an incipient outbreak phase then progressed into larger diameter stems (Schmid et al 2007). They are also consistent with studies that reported drought-related MPB outbreaks led to mortality rates skewed away from the large-diameter ponderosa pines that exceeded 51.0 cm DBH within the Warner Mountains of California and Elkhorn Mountains of Montana (Egan et al 2010;Randall et al 2011).…”

“…Bark beetle outbreak phases have been characterized into four unique categories of endemic, incipient, epidemic, and post-epidemic (Safranyik and Carroll 2006;Schmid et al 2007). The endemic phase is characterized by having an individual-tree spatial pattern of attack with no clustering, epidemics have clusters C5 trees per attacked group, and the incipient phase is between these thresholds (Sartwell and Stevens 1975).…”

“…Insect behavior during an outbreak fluctuates through various phases of an outbreak that lead to differences in the size, quality, and quantity of mass-attacked trees, degree of spatial clustering in host mortality, beetle dispersal distance to new host trees, and population control mechanisms (Sartwell and Stevens 1975;Safranyik and Carroll 2006;Kautz et al 2011;Walter and Platt 2013). Common characteristics describing these phases have been summarized for the mountain pine beetle (D. ponderosae) (MPB) within lodgepole pine (P. contorta) forests (Safranyik and Carroll 2006;) and, to a lesser extent, for ponderosa pine (P. ponderosa) systems (Schmid et al 2007). Only limited study of outbreak phases have occurred for other bark beetles in western North America, and no evaluation of JPB-caused mortality patterns during these phases has occurred to-date.…”

Large-Scale Thinnings, Ponderosa Pine, and Mountain Pine Beetle in the Black Hills, USA

“…At 13%, the treated stands are maximizing tree growth and will presumably be more vigorous, which according to previous studies, translates to higher tree resistance (Larsson et al 1983, Waring andPitman 1985). This suggests that treated stands are positioned to benefit over the long-term from thinning by maintaining lower susceptibility to bark beetle attacks until increased tree growth carries them to a susceptible state again (Schmid et al 2007). Consistent with these findings Oliver (1995) examined even-aged ponderosa pine stands in California and reported substantial mortality when the relative SDI was Ͼ54% (based on a maximum SDI of 450 as used in this study).…”