A method of site quality evaluation for red alder.

Abstract

A field guide to predict site index for red alder (Alnus rubra Bong.) was developed for use in western Washington and Oregon. The guide requires the user to evaluate 14 soil-site properties that are grouped into three general factors: (1) geographic and topographic position, (2) soil moisture and aeration during the growing season, and (3) soil fertility and physical condition. Construction of the guide was modeled after a method of site evaluation developed for several southern hardwood species. The red alder model is accurate when used properly. The correlation (r) between predicted and measured site index was 0.97 for the basic data set of 25 plots and 0.96 for the 15 plots used for verification. Estimated site index should be within ¡À 2 meters of measured site index 95 percent of the time. Use of a second independent data set for model verification resulted in a somewhat lower correlation (r = 0.89) between measured and predicted site index than was achieved with the original data set, but the model continued to meet the accuracy standard of ¡À 2 meters (p¡Ü0.05).

Citation

Harrington, Constance A. 1986. A method of site quality evaluation for red alder. Gen. Tech. Rep. PNW-GTR-192. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 22 p