Bark Beetle-Fire Associations in the Greater Yellowstone Area

The large forest fires in and around Yellowstone National Park in 1988 bring up many ecological questions, including the role of bark beetles. Bark beetles may contribute to fuel buildup over the years preceding a fire, resulting in stand replacement fires. Fire is important to the survival of seral tree species and bark beetles that reproduce in them. Without fire, seral species are ultimately replaced by climax species. Following fire, bark- and wood-boring beetles respond to fire-injured trees. Because of synchrony of the fires and life cycles of the beetles, beetle infestation in 1988 was not observed in fire-injured trees. However, endemic populations of beetles, beetle infestation in 1988 was not observed in fire-injured trees. However, endemic populations of beetles, upon emergence in 1989, infested large numbers of fire-injured trees. Of the trees examined in each species, 28 to 65 percent were infested by bark beetles: Pinus contora (28 percent) by Ips pini:; Pseudotsuga menziesii (32 percent) by Dendroctonus pseudotsugae; Picea engelmannii (65 percent) by Dendroctonus rufipennis; and Abies lasiocarpa (35 percent) by Buprestidae and Cerambycidae. Most trees infested by bark beetles had 50 percent or more of their basal circumference killed by fire. Bark beetle populations probably will increase in the remaining fire-injured trees

Interactions Between Fire-Injured Trees and Insects in the Greater Yellowstone Area

After the 1988 Greater Yellowstone Area (GYA) fires, 24 permanent plots were established at 6 sites within 4 different burned areas. The purpose was to evaluate the effects of fire injury on susceptibility to insect attack and tree survival. Mensuration, fire injury, and insect attack data were collected on four species of burned conifers. By July 1991 76 percent of the 125 Douglas-fir had been infested by bark beetles and wood borers; 58 percent of the 151 lodgepole pine were infested; 82 percent of the 17 Engelmann spruce were infested; and 88 percent of the 17 subalpine fir were infested. Fire injury combined with subsequent insect attack resulted in death to 55 percent of the Douglas-fir, 69 percent of the lodgepole pine, 82 percent of the Engelmann spruce, and all of the subalpine fir

Bark Beetle and Wood Borer Infestation in the Greater Yellowstone Area During Four Postfire Years

Extensive surveys of bark beetles and wood bores in the Greater Yellowstone area were conducted in 1991 through 1993. The study objectives were to determine the effect of delayed tree mortality following the 1988 fires on mosaics of fire-killed and green tree stands, the relationship between fire injury and subsequent infestation, and the effect of insect buildup in fire injured trees on infestation rates for uninjured trees. Surveys were conducted adjacent to roads, and plots wee selected randomly. In 1991, 321 plots were measured, 198 plots in 1992, and 127 plots in 1993. Insects killed 12.6 percent of the Douglas-fir, 17.9 percent of the lodgepole pine, 6.6 percent of the Engelmann spruce, 7.5 percent of the subalpine fire, and 2.8 percent of the whitebark pine. Delayed mortality attributed to fire injury accounted for more mortality than insects. Both types of mortality greatly altered the original fire-killed/green tree mosaics that were apparent immediately after the 1988 fires. Insect infestation was strongly and positively correlated with the percent of the basal circumference of the tree that was fire killed in the species, except in Engelmann spruce where infestation peaked in the middle fire-injury class. Infestation in Douglas-fir, lodgepole pine, and Engelmann spruce increased through 1992 then declined in 1993. Although it cannot be said with certainty that insects built up in fire-injured trees and then caused increased infestation of uninjured trees, the high level of infestation suggests this is the case

Demonstration of the effectiveness of basal area cutting to reduce tree killing by the mountain pine beetle in ponderosa pine, Crow and Northern Cheyenne Indian Reservations, Montana, 1984 : establishment report

During 1984, a demonstration project was established on the Crow and Northern Cheyenne Indian Reservations to determine the effectiveness of basal area cutting in second-growth ponderosa pine stands to reduce losses to the mountain pine beetle. This project will help develop management strategies for susceptible stands in eastern Montana. Four treatments, replicated twice on each Reservation, will be implemented: reduction of existing basal area through partial-cutting to 50, 65, and 80 square feet/acre and no-cutting (control). After treatment, each block will be monitored yearly for the first 5 years, then at 5-year intervals for 20 years

Lodgepole Pine Vigor, Regeneration, and Infestation by Mountain Pine Beetle Following Partial cutting on the Shoshone National Forest, Wyoming

Lodgepole pine stands were thinned in the Shoshone National Forest of northwestern Wyoming in 1979 and 1980 using different forms of partial cutting. Average losses of trees 5 inches diameter at breast height and larger to mountain pine beetles during the 5 years following thinning ranged from less than 1 percent in spaced thinnings to 7.4 percent in the 12-inch diameter limit cut, compared to 26.5 percent in check stands. Residual trees increased radial growth significantly, but change in growth efficiency is slow. Regeneration 5 years after thinning ranged between 1,160 and 3,560 seedlings per acre, with pine being favored in the more open stands

Temperature-Dependent Development of the Mountain Pine Beetle (Coleoptera : Scolytidae) and Simulation of its Phenology

Temperature-dependent development of the egg, larval, and pupal life-stages of the mountain pine beetle (Dendroctonus ponderosae Hopkins) was described using data from constant-temperature laboratory experiments. A phenology model describing the effect of temperature on the temporal distribution of the life-stages was developed using these data. Phloem temperatures recorded in a beetle-infested lodgepole pine (Pinus contorta Douglas) were used as input to run the model. Results from model simulations suggest that inherent temperature thresholds in each life-stage help to synchronize population dynamics with seasonal climatic changes. This basic phenological information and the developed model will facilitate both research and management endeavors aimed at reducing losses in lodgepole pine stands caused by mountain pine beetle infestations

Microclimate : An Alternative to Tree Vigor as a Basis for Mountain Pine Beetle Infestations

Microclimates of thinned and unthinned stands of lodgepole pine (Pinus contorta var. latifolia) were monitored and related to mountain pine beetle (Dendroctonus ponderosae) response on the north slope of the Uinta Mountains in northeastern Utah. Thinning increased light intensity, wind movement, insolation and temperature. Fewer beetles were caught in pheromone-baited traps in the thinned stand than in the unthinned stand. Beetles killed 2% of trees in the thinned stand and 16% in the unthinned stand

Bark Beetle Activity and Delayed Tree Mortality in the Greater Yellowstone Area Following the 1988 Fires

After the 1988 Greater Yellowstone Area fires two studies were begun to monitor beetle activity in burned and unburned conifers and to evaluate the susceptibility of fire injured trees to bark beetle attack. An intensive survey was conducted annually from 1989 through 1992 on 24 permanent plots located in or near stands burned by surface fire. Stands were located adjacent to areas of extensive crowning and torching. By August 1992, 79% of the 125 Douglas-fir had been infested by bark beetles (primarily by the Douglas-fir beetle) and wood borers; 62% of the 151 lodgepole pine were infested (primarily by the pine engraver); 94% of the 17 Engelmann spruce were infested (primarily by the spruce beetle); and 71% of the 17 subalpine fir were infested (primarily by wood borers). Fire injury combined with subsequent insect attack killed 77% of the Douglas-fir, 61% of the lodgepole pine, 94% of the Engelmann spruce, and all of the subalpine fir. An extensive survey was conducted in 1991 and 1992 on 519 randomly located plots throughout the area. Plots were located in unburned and surface fire-burned areas. Insects killed 13% of the 1,012 Douglas-fir, 18% of the 4,758 lodgepole pine, 7% of the 439 Engelmann spruce, 8% of the 134 subalpine fire, and 3% of the 144 whitebark pine. Foe all species, insect infestation increased with the percent of the basal circumference killed by fire, except for Engelmann spruce where infestation was greatest with 40 to 80% of the basal circumference girdled. Infestation in Douglas-fir, lodgepole pine, and Engelmann spruce increased with time. The age level of infestation suggests that insect populations increased in fire-injured trees and the spread to uninjured trees. Increases form 1991 to 1992 suggest that additional tree mortality will occur in 1993, and that a major outbreak could occur in Engelmann spruce. Delayed tree mortality attributed to fire injury accounted for more mortality than insects. Both types of mortality greatly altered the original mosaics of green trees and dead trees that were apparent immediately after the 1988 fires

Mountain Pine Beetle Dynamics in Lodgepole Pine Forests, Part 1: Course of an Infectation

Much of this work is original research by the authors. However, published literature on the mountain pine beetle is reviewed with particular reference to epidemic infestations in lodgepole pine forests. The mountain pine beetle and lodgepole pine have evolved into an intensive and highly compatible relationship. Consequently, stand dynamics of lodgepole pine is a primary factor in the development of beetle epidemics. the diameter-growth relationship and the effects of environmental factors on the beetle population provide the basis for assessing potential tree losses and some forest management alternatives to be used. Stand susceptibility and acceptable risk are considered in the use of these management alternatives in order to achieve management\u27s goals