A Model for Tree-Ring Time Series to Detect Regional Growth Changes in Young, Evenaged Forest Stands

Abstract

Time-related region-wide growth declines or increases due to environmental impacts are not readily detected in rings of young trees because the intrinsic age-related decrease in ring widths is too prominent. Standardization techniques often obscure gradual growth changes due to exogenous factors such as regional atmospheric deposition. The model presented here uses a linear aggregate analysis of ring widths that permits age to be held constant while time varies. Rigorous testing requires tree-ring observations from evenaged stands exhibiting a range of current ages normal for the species and region. With age held constant, the key variable is simply the calendar year to which given rings are dated, a measure of the passage of time. An application of the model is given in which a 36 -year growth decline is identified in 20- to 40- year-old Pinus taeda L. in the southeastern United States.