Site index curves for young-growth California white fir were developed by using stem analysis data from 77 dominant and codominant trees growing in mixed-coniferstands on the western slopes of the Sierra Nevada. Site index reference age is 50 years at breast height. A family of 11 curves is presented for site index estimation. For more precise estimates, the site index estimating equation can be solved by using appropriate values of total tree height and breast-height age.
Mixed-conifer forests are the largest vegetation type in California, covering more than 13 million acres (Barbour and Major 1977). This type, the Sierra Nevada Mixed Conifer (Society of American Foresters Forest cover type 243, Tappeiner 1980) dominates mid-elevations of the Sierra Nevada's western slopes. The extent of the mixed-conifer type and the amount of timber harvested from the west slopes of the Sierra Nevada emphasize the need for accurate growth and yield prediction methods for this area.
In a 1964-1967 study on the Challenge Experimental Forest, seedfall was evaluated in 2-, 5-, and 10-acre circular clearcuttings. During the 4 years, 10 seed crops, ranging from light to bumper, were produced by ponderosa pine. white fir, Douglas-fir, and incense cedar. Seedfall ranged from 76 to 40,691 sound seed per acre (188 to 100,547/ha) for a single species in a given year. From 89 to 100 percent of each species' seed fell within an area 1 1/2 times the height of the average dominant tree. Overall, seed distribution was highly variable.
Foresters often need information on the cost effectiveness of manual and chemical release treatments for individual and combined species in young mixed-shrub communities. A study in northern Califomia evaluated five manual and chemical treatments and their effect on several shrubs and grasses. Treatments were grubbing at age 1 to 2- and 4 ft (0.6- and 1.2-m) radii, regrubbing and expanding the 2-ft radii to 4 ft, regrubbing and expanding the 4-ft radii to 6 A (1.8 m) at age 4, and applying Velpar herbicide to the entire plot at age 2. Five years after initial manual release and 4 years after chemical release, ponderosa pine (Pinus ponderosa Dougl. ex Laws. var. ponderosa) stem caliper at 12 in. (30 cm) above mean ground line differed significantly between Velpar and the untreated control, 2-ft radius, 4-ft radius, and 2-ft radius expanded to 4 ft. Expanding the radius from 4 to 6 feet provided a pine stem caliper that differed significantly from that in the control, and the 2-ft and 4-ft radii treatments. Additional analyses with ponderosa pine seedling height also indicated significant differences among treatmenu that were generally similar to those above. Differences among the six treatments, which are presented in 15 comparisons of stem caliper and treatment production rates, provide forest managers with growth and cost comparisons, and should aid them in selecting the release treatment best suited to their particular situation.
Summaries from 49 published articles on site-index and dominant-heightgrowth curves and equations are presented for 20 tree species or species groups found in California, Oregon, Washington, British Columbia, southeastern Alaska, Idaho, and western Montana. The summaries are organized by species. Each summary describes the modeling approach, type of curves/ equations, base age, and type of age presented in the article. In addition, the geographic location, number of trees or plots, range in age, and range in site index used to develop the curves/equations are also described.
