DEVELOPMENT OF A MIXED SHRUB-TANOAK-DOUGLAS-FIR COMMUNITY IN A TREATED AND UNTREATED CONDITION

On a medium site in northern California, a tanoak-mixed shrub communit y was given several treatments (manual release two and three times, a combination chainsaw and cut surface herbicide treatment, two foliar h erbicides, and a tank mix of the two herbicides) to study its developm ent in both a natural (control) and treated condition. The herbicides were 2,4-D, Garlon 3A, and Garlon 4, each applied two times. Survival of planted Douglas-fir seedlings was recorded for 11 years and growth was quantified for 9 years after the last treatment application. In ad dition to Douglas-fir, data are presented individually for the two mos t abundant species (tanoak and snowbrush), for greenleaf manzanita, an d for the hardwood tree and shrubs combined. At the study's end in 199 5 combined vegetation in the control had a mean density of 1,800 plant s per acre, foliar cover of 23,700 ft(2) per acre, and height of 11.2 feet. In contrast, combined tree and shrubs in the most effective trea tment for controlling them--cut and spray Garlon 3A--had a mean densit y of 150 plants per acre, foliar cover of 150 ft(2) per acre and heigh t of 5.9 feet at study end. And because competition for site resources was low Douglas-fir seedlings developed best in this treatment. Mean Douglas-fir diameter was 4.6 inches at 12 inches above mean ground lin e, height averaged more than 21 feet, and mean foliar cover was 39,850 ft(2) at the end of the study. The cost was $227 per acre. The treatm ent response data, cost information, and plant community relationships provide the forest land manager with knowledge on how to attain some specific plant communities in the future, and their developmental pote ntials.