White fir regeneration and growth coincides with adequate or above normal moisture, which allows this species to occupy sites once dominated by more drought-tolerant pine species. During protracted drought periods, however, white fir mortality exceeds acceptable amounts and affects management goals in many watersheds. Although the majority of the white fir mortality associated with the recent drought happened before 1994, some areas are still experiencing dramatic increases in tree decline and death. Lodgepole pine . In the northeast part of this ecological section, lodgepole pine is mainly in frost pockets or along riparian areas.
Many stands have chronic mortality despite normal precipitation.
During droughts, increased mountain pine beetle activity contributes to even higher rates of tree mortality. Over the past two years, increases in tree mortality have been observed primarily on the Truckee District, Tahoe National Forest, and at Donner Memorial State Park. Tree mortality is apparent along the Truckee River in and around campground sites and in undeveloped areas. Conifer health declined suddenly near Horseshoe Lake on the Inyo National Forest in 1992. Extensive mortality and severe needle loss were observed on 15 acres, which included primarily lodgepole pine but also red fir, mountain hemlock, and western white pine.