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

Abstract

Dendroecological techniques were used in this study to compare the radial growth patterns of different conifer species and to identify regional climatic anomalies and spruce beetle ( Dendroctonus rufipennis Kirby) outbreaks for the past four centuries in the McGregor Model Forest, central British Columbia, Canada. Tree-ring chronologies of Douglas-fir ( Pseudotsuga menziesii var. glauca (Beissn.) Franco), subalpine fir ( Abies lasiocarpa (Hook.) Nutt.), and interior spruce ( Picea engelmannii Parry × P. glauca (Moench) Voss) were developed for the Model Forest. Response function analysis showed that (1) Douglas-fir is the most climate sensitive species, and its radial growth is mainly controlled by spring precipitation and early summer temperature, and (2) the ring growth of subalpine fir and spruce is negatively affected by high summer temperature. Comparisons of the tree-ring chronologies among the three species revealed dynamics of growth releases and suppressions which reflected climate variations and forest disturbance patterns in the past several centuries. The climate during the late 1750s–1800s was characterized by slightly moist springs and probably moderate summers. During the late 1860s and early 1870s, the region experienced dry springs, hot summers, and probably cold late falls. This study identified three intervals of major disturbances attributable to severe spruce beetle outbreaks: the late 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 climate anomalies and spruce beetle outbreaks could provide insight into the dynamics of forest growth and its response to environmental changes.