On a medium site in northern California, a mostly shrub community was treated by two manual release techniques and by two herbicides, to study its development in both a natural (control) and treated condition. Survival and growth of planted ponderosa pine seedlings were quantified for 8 to 11 years after initial treatment applications. Treatments included manual release in a 4-foot radius around pine seedlings one, two, and three times; grubbing the entire one-seventh acre plot two times; applying 2, 4-D and Velpar herbicides to the entire plot one time; and a control. Data are presented for the most abundant species (greenleaf manzanita), second most abundant species (snowbrush), by the two species combined, and by all 10 shrub species combined. At the end of the study in 1990, manzanita was the most abundant species with 15,267 plants per acre, cover of 24,800 ft2, and height of 5.4 feet. Ponderosa pine developed best in plots where the entire area was grubbed twice (mean diameter at 12 inches above ground of 6.3 inches) and in the Velpar-treated plots (mean height of 14.2 feet). The cost of grubbing the entire area twice was almost $1,700 per acre. Applying Velpar, including cost of the the chemical, was about $100 per acre. Site preparation without subsequent release led to a brushfield similar to that present before the study began.
McDonald, Philip M.; Fiddler, Gary O. 1995. Development of a mixed shrub–ponderosa pine community in a natural and treated condition. Res. Paper PSW-RP-224. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture; 19 p