The relationship between tree diameter growth and climate for coniferous species in northern California

The difference between actual and predicted growth rates for the conifer re gions of northern California has been observed to vary with climatic change s. This study presents a method to investigate the relationship between gro wth and climate. Growth variations attributable to biological and cultural factors were removed by using the CACTOS (California conifer timber output simulator) program. The remaining variation was then associated with relati ve precipitation and temperature for the projected period and the CACTOS ca libration period. Climatic data from the current and preceding years were c onsidered. Elevation, stand density, and species were also investigated to determine their effects on the format and magnitude of the relationship bet ween growth and climate. The results of this study, which included tests of stem analysis data taken over 15 years, indicate that growth variation is associated with the climatic changes of winter precipitation and summer tem peratures for the region, in addition to biological and cultural factors. W inter precipitation and summer temperatures affect growth in the current an d the subsequent years. Moreover, the relationship between climate and grow th changes by densities and species. This study provides a basis for using short-term growth data to make long-term growth projections with growth adj usted to long-term climatic conditions.