Competition between trees in brush-free plots began during the eighth year for trees spaced 6 by 6 feet and during the tenth year for trees spaced 9 by 9 feet.

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.