Book Description

Multivariate regression analysis was used to explore the relationship of weather and tree growth to the average volume of Abies concolor sawtimber killed annually by fir engraver (Scolylus ventralis Lec.) and roundheaded fir borer (Tetropiurn abietis Fall) beetles. Data for the years 1944 to 1954 from 22 plots in northern California showed that white fir mortality increased in years when (a) fir radial growth during the cunent and previous 2 years declined an average of 2.5 percent per year, (b) precipitation during the current and previous years averaged 11 percent below normal, or (c) spring precipitation averaged 32 percent below normal. Levels of mortality were related chiefly to regional fluctuations in radial growth of dominant and intermediate fir.