Dendroecological studies of tree growth, climate and spruce beetle outbreaks in Central British Columbia, Canada

Dendroecological techniques were used in this study to compare the radial g rowth patterns of different conifer species and to identify regional climat ic anomalies and spruce beetle (Dendroctonus rufipennis Kirby) outbreaks fo r the past four centuries in the McGregor Model Forest, central British Col umbia, Canada. Tree-ring chronologies of Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) France), subalpine fir (Abies lasiocarpa (Hook.) Nut t.), and interior spruce (Picea engelmannii Parry x P. glauca (Moench) Voss ) were developed for the Model Forest. Response function analysis showed th at (1) Douglas-fir is the most climate sensitive species, and its radial gr owth is mainly controlled by spring precipitation and early summer temperat ure, and (2) the ring growth of subalpine fir and spruce is negatively affe cted by high summer temperature. Comparisons of the tree-ring chronologies among the three species revealed dynamics of growth releases and suppressio ns which reflected climate variations and forest disturbance patterns in th e past several centuries. The climate during the late 1750s-1800s was chara cterized by slightly moist springs and probably moderate summers. During th e late 1860s and early 1870s, the region experienced dry springs, hot summe rs, and probably cold late falls. This study identified three intervals of major disturbances attributable to severe spruce beetle outbreaks: the Bate 1720s, 1810s-1820s, and 1960s-early 1980s. These coincided with periods of above average growth in Douglas-fir. The association suggested a possible moist spring-outbreak pattern. The multicentury tree-ring records of climat e anomalies and spruce beetle outbreaks could provide insight into the dyna mics of forest growth and its response to environmental changes. (C) 1999 E lsevier Science B.V. All rights reserved.