Early survival and growth of planted Douglas-fir with red alder in four mixed regimes.

Abstract

To quantify between-species interactions, we measured and compared survival and growth of planted Douglas-fir and associated planted and volunteer red alder at a location on the west side of the Cascade Range in Washington. The planted alder were wildlings dug either from a nearby area or from a distant, coastal site and interplanted into a 3-year-old Douglas-fir plantation. The volunteer alder became established in year 1; these were cut at year 3 or 7 depending on the regime tested.

The data indicated no apparent advantage in using nonlocal red alder to reduce aboveground competition with Douglas-fir at this location. Survival of both sources of interplanted alder was high, and the average diameter and height were similar through plantation age 10. Retaining about 1100 volunteer alder per hectare (445/acre) through plantation age 7 had no measurable positive or negative effect on the associated Douglas-fir.

When alder densities are less than about 1 250/ha (500/acre), silviculturists can safely delay alder control on most average or below-average site quality land until 6 to 8 years after planting Douglas-fir. This reduces alder sprouting and permits combining complete or partial control of alder with precommercial thinning of associated Douglas-fir. To ensure timely control, periodic observations of Douglas-fir red alder mixtures are necessary, however.

Citation

Murray, Marshall D.; Miller, Richard E. 1986. Early survival and growth of planted Douglas-fir with red alder in four mixed regimes. Res. Pap. PNW-RP-366. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 13 p