Ponderosa pine seedlings and competing vegetation: ecology, growth, and cost

Foresten oftm need information on the cost effedivenessofmanual and chemical release treatments for individual and combined species in young mixed-shrub communities. A studvin northern Califomia evaluated fivemanual and chemical treatmcnts and their effect an several shmbs and grasses. Treatments were grubbing at age 1 to 2-and 441 (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 Velparherbicide to the entire plot at age 2. Five yean after initial manual release and 4 yean after chemical releare, ponderosa pine (Pinus ponderoso Dougl. ex Laws. var. ponderosa) stem caliper at 12 in. (30 cm) above mean ground line d a r e d significantly k w e e n Velpar and the untreated cmIml. 2-ft radius, 441 radius, and 2-ft radius expanded to 4 ft. Expanding the radius from 4 to 6 feet provided a pine stem caliper that d i f f e d 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 thesixtreatmentr, which arepresented in 15 canparirons of stem caliper and treatment production rates, provide forest managers with growth and cost cmparisans, and should aid them in seleeling the release treatment best suited to their particular situation. When foresters contemplate releasing young conirer plantations , they often ask: What is the most cCfecdve lrcallnent and how cost effective is it? A related question usually follows: Whenis thebest time to apply the treatment? Theccntral thcme of the study reported here, which is one of many in a National Forest Service Administrative Study on vegetation management , addresses these questions. A 1-year-old ponderosa pine plantation on the Shasta-Trinity National Foresls in northern California was released Crom mixed shrubs and grasses by several manual and chemical techniques. Around selected seedlings a 2-it (0.6-m) radius was grubbcd, and around others a 4-ft (1.2-m) radius. At age4, half of the 2-Ctradii wereregrubbcdand expanded to4-ftradii, and halfof the 4-ft radii were regrubbed and expanded to 6-ft (1.8-m) radii. Other areas were Ueated with Velpar herbicide at age 2. Two years after Velpar was applied, stem caliper and height of ponderosa pines in this Lreatmcnt differed at the 5 pcrccnt level from counterpartsin thelcastintensive trcauncnts(contro1, 2-ft,4-ft, and 2-11 expanded radii)-the fist …