Predicting Release of Advance Reproduction of Mixed Conifer Species in California Following Overstory Removal

Phase I of this study was aimed at determining the most important variables influencing post-release height growth of white fir. Of the 17 variables measured on 96 samples, the most important were pre-release height growth, live crown ratio, and pattern of height growth which accounted for 46 percent of the variability. The addition of four more factors accounted for an additional 10 percent of the variability. Average time before response was between 2 and 4 years. The three most important factors affecting post-release diameter growth rate were prerelease diameter growth rate, diameter, and pre-release height which accounted for 67 percent of the variability. In Phase II, the sample was enlarged to a total of 592 trees of white fir, red fir, and Douglas-fir. Discriminant analysis was used to characterize trees which were likely to exceed alternative levels of average annual post-release height growth. Using pre-release height growth and live crown ratio, the post-release height growth of each species was correctly classified 63 to 84 percent of the time. Independent samples of 30 trees of each species used to validate the model were correctly classified 45 to 100 percent of the time. Forest Sci. 31:3-15.