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General Technical Report
Title: Risk-rating systems for mature red fir and white fir in northern California
Author: Ferrell, George T.
Source: Gen. Tech. Rep. PSW-39. Berkeley, CA: Pacific Southwest Forest and Range Exp. Stn., Forest Service, U.S. Department of Agriculture; 29 p
Station ID: GTR-PSW-039
Description: On the basis of crown and bole characteristics, risk-rating systems to predict the probability that a tree will die within 5 years were developed for mature red fir and white fir in northern California. The systems apply to firs at least 10 inches (25.4 cm) in diameter-at-breast-height (d.b.h.), growing in mature stands, with the original overstory at least partially intact. From 1975 to 1977, 1012 red firs (851 live, 161 dead) and 2571 white firs (2430 live, 141 dead) were examined in virgin and cutover stands. Tree characteristics were selected and used as predictor variables in regression equations. The risk equations were then translated into Award-Penalty Point Systems for field use. A tree is awarded points on the basis of ratings of some characteristics, and penalized points on the basis of ratings of others. The difference between the Award and Penalty Point Totals-the Risk Point Total-is the value used to predict a tree's death within 5 years. This report describes studies designed to develop, test, and extend the risk-rating systems. Properly used, these systems should contribute to the sound, long-term management of California's true firs.
Key Words: Abies concolor, Abies magnifica, California, mortality, risk rating, bark boring insects.
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Ferrell, George T. 1980. Risk-rating systems for mature red fir and white fir in northern California Gen. Tech. Rep. PSW-39. Berkeley, CA: Pacific Southwest Forest and Range Exp. Stn., Forest Service, U.S. Department of Agriculture; 29 p.