Recovery Plan for the Northern Spotted Owl - DRAFT

CaliforniaAsrow (1983) sampled the vegetation of four occupied spotted owl managementareas (SOMAs) in old-growth Douglas-fir/white fir forests on the Scott RiverRanger District of the Klamath National Forest. Owl presence was documentedusing a combination of night and day surveys during the 1983 breedingseason. Vegetation was sampled on six variable-radius plots in each SOMA.One plot was centered on the location of the bird; other plots were placed 132feet from the central plot and equal distances from each other.Bingham (1991) described stands used by 20 radio-transmittered owls forroosting and foraging in Douglas-fir/tanoak/madrone forests on the Mad RiverRanger District (Six Rivers National Forest) in the Klamath province. Utilizedstands were defined as those with more than 3 telemetry locations. Data weresummarized separately for roosting stands (based on daytime locations) andforaging stands (based on nighttime locations) in the breeding and nonbreedingseason. Vegetation was sampled on 3 to 8 0.25-acre plots per stand. Theauthor presented the data as means for each of three vegetation classes(defined on the basis of a cluster analysis): the data presented in this appendixare' the means of these three classes, weighted by sample sizes.Blakesley et al. (1992) recorded 421 owl locations, including 79 nest sites,during the breeding seasons of 1985 to 1989 in the Willow Creek study area innorthwest California. Stand types were defined by dominant vegetation (conifers,hardwoods, unvegetated), mean dbh, elevation, aspect, position (lower,middle, or upper third), and slope.Chavez-Leon (1989) measured habitat structure in 14 stands used by owlsduring 1987 and 1988 in the Klamath province (Humboldt and MendocinoCounties) in northwestern California. Pairs occupied nine and 10 sites in 1987and 1988, respectively: nesting pairs occupied five and three sites in 1987 and1988, respectively. Twelve of the 14 sites were in typical Douglas-fir/tanoak/madrone forests, and two were in redwoods. The landscape was highly fragmented:stands used by owls sometimes were fragmented and varied in sizefrom 49 to 642 acres. Habitat structure was measured on five or more variable-radiusplots randomly placed within each stand. Chavez-Leon excludedsome plots in calculating mean densities and basal areas, but we used all plotsfor our analysis.Folliard and Reese (1991) measured 30 nest sites and nest stands during 1990in second-growth redwood/Douglas-fir forests of the California Coast province(Humboldt and Del Norte Counties). Plots were circular and covered 0.18 acres(radius = 50 feet). Nest-site plots were centered on the nest but did not includethe nest tree in measures of density and basal area. Four or five plots weredistributed randomly within 0.5 miles of the nest and in the nest stand.Jimerson et al. (1991a) quantified the structure of old-growth Douglas-fir/tanoak/madrone stands in SAF 234 (i.e., Society of American Foresters foresttype 234) in the Klamath province. Data were collected on the Six Rivers,Siskiyou, and Klamath (western half National Forests, and the NorthernCalifornia Coast Range Preserve. Vegetation was sampled on three variableradiusplots in each old-growth stand. Bingham and Sawyer (1991) presenteda summary of this information.Jimerson et al. (1991b) quantified the structure of old-growth Pacific Douglasfirforests stands in SAF 229 in the Klamath province. Data were collected onthe western half of the Klamath and Six Rivers National Forests. Vegetationwas sampled on three variable-radius plots in each old-growth stand.291