A Silvicultural Assessment Of 10 Lodgepole Pine Stands After Partial Cutting To Reduce Susceptibility To Mountain Pine Beetle

Over the past 15 years, selective cutting prescriptions have been applied by forest operations in southeastern British Columbia as part of a strategy to reduce landscape-level susceptibility to damage from mountain pine beetle outbreaks. The prescriptions have been applied in stands where maintenance of some mature forest cover is needed to meet management objectives for viewscapes, recreation and habitat or to hold some pine volume during periods of rising beetle activity until it is required or available for harvest. In this study, we examined 10 of these sites 5 to 14 years after harvest, and determined current stand composition and structure from direct sampling and pre- and post-treatment stand characteristics from stand reconstruction. We then related these characteristics to original treatment specifications; the volume removed during harvest and remaining on site after treatment; subsequent losses to wind, snow or bark beetle damage; current stocking status; radial growth rates of residual overstorey trees; and the nature of fuel complexes created and effects of treatment on potential fire behaviour.

Periodic diameter and basal area growth were determined for partially cut stands of lodgepole pine at five locations over approximately 10 year periods. After cutting, average diameters in the partially cut plots generally increased by 0.8 inches or more, while average diameter in the uncut controls increased by 0.6 inches or less. Diameter growth in the partially cut plots was generally significantly greater than diameter growth in the controls. Individual tree growth is discussed in relation to potential susceptibility to mountain pine beetle infestation. Basal area decreased in three of the four GSL (growing stock level) 40 stands because of windthrow. Basal area generally increased >1.0 ft 2 / acre/year in partially cut plots except in the GSL 40 stands with substantial windthrow and one GSL 100 with an Armillaria infection pocket. Basal area increases in the control plots ranged from 0.2 to 1.1 ft 2 /acre/year, although the one control with a BA growth rate of 1.1 ft 2 /acre/year had a relatively low initial BA. Data from the stands are employed in the susceptibility rating methods of Amman et al.(1977), Shore and Safranyik (1992),and Anhold et al. (1996 to determine stand susceptibility and the results discussed in terms of general applicability of these methods to partially cut stands. Basal area growth is used to estimate the length of time required for various stand densities to reach specific susceptibility thresholds for mountain pine beetle infestation. Several of the GSL 40 stands are not projected to reach the susceptibility thresholds in 100 years because of windthrow. Barring mortality 1%,GSL 80 stands are estimated to reach the basal area threshold of 120 ft 2 per acre in

"The purpose of this study was to compare and contrast microclimatic and fine fuel moisture conditions in a natural stand of mature lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) with an adjacent stand which was thinned to a uniform 4-m spacing between stems with respect to: within-stand microclimate elements that are likely to affect the moisture content of fine, dead surface fuels; measured moisture content of fine, dead surface fuels; and, differences between the actual moisture content of lodgepole pine needle litter versus equivalent values predicted by the Canadian Forest Fire Weather Index (FWI) System (Van Wagner 1987)."--Document.