http://worldcat.org/entity/work/id/2487616650

Surveys to measure tree damage caused by a western spruce budworm outbreak on the Carson National Forest, 1984 and 1991

"In 1984 a survey using double sampling techniques was conducted in a portion of the Carson National Forest, New Mexico, to measure the damage to mixed conifer stands caused by a persistent oubreak of the western spruce budworm. The method used was a stratified random sampling design using color infrared aerial photography followed by ground truth. In 1991, using the 1984 aerial photographs to located the primary sampling units, the ground portion of the survey was repeated with slight modification. A statistical analysis of survey accuracy showed good agreement with photo interpretation (stratification) and ground sampling, and that stratification into 4 damage classes improved survey efficiency, particularly with the larger trees in the more heavily damaged areas. Forest composition was primarily Douglas-fir, followed by Engelman spruce, white fir and corkbark fir. Non-host species made up 13 percent of the stands. Douglas-fir suffered the heaviest mortality and permanent crown damage. In the two heaviest damage strata, white fir was the second most abundant host species, while in the two least damaged strata, Engelmann spruce was the second most abundant host species. The smaller diameter classes of all host species experienced the most damage. There was no consistent relationship between stand density and damage, but the two extreme basal area densities of 115.3 ft.² and 158.3 ft.² occurred in the no-damage and dead strata, respectively. The relative abundance of Douglas-fir increased with increased damage. Reproduction was considered ample, but varied considerably between damage strata. It was recommended that, where practical, future damaging outbreaks of the western spruce budworm could be minimized by reducing the basal area, removing the shade tolerant host trees (primarily the larger white firs) and favoring the nonhost species, particularly ponderosa pine. It was also suggested that the survey be repeated at 4 to 5 year intervals to monitor the stands recuperative abilities, to record changes in succession and to evaluate future budworm outbreaks and impacts."

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