Mechanical and chemical release treatments applied to a 16-year-old pine plantation

Abstract

To increase the growth of planted conifer saplings, the competing vegetation in a 16-year-old pine plantation on the Plumas National Forest in northern California was mechanically treated with the Tracmac mechanical cutter. The large size of this vegetation (chinkapin, greenleaf manzanita, whitethorn, huckleberry oak) eliminated other release methods as feasible alternatives. Additional treatments were a chemical treatment, in which 2,4-0 was applied to a portion of the study site that had been treated with the Tracmac 2 years previously, and untreated control. Eleven growing seasons after treatment, mechanical release alone did not significantly increase diameter, height, or crown cover of the pines compared to the control. In contrast, the Tracmac plus herbicide (chemical) treatment statistically increased conifer crown cover compared to the other two treatments. Pine diameter and height were also larger in the chemical treatment than in the other two treatments, but not significantly. Mean crown cover was 120 percent greater in the saplings in the chemical treatment than for pines in the control, height was 35 percent greater, and diameter was 50 percent greater. Relative costs were $218 per acre for the mechanical treatment and $267 per acre for the Tracmac plus herbicide (chemical). The most cost-effective treatment was Trac-mac plus herbicide.

Citation

Fiddler, Gary O.; McDonald, Philip M.; Mori, Sylvia R. 2000. Mechanical and chemical release treatments applied to a 16-year-old pine plantation. Res. Note PSW-RN-425. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 11 p