Size‐, species‐, and site‐specific tree growth responses to climate variability in old‐growth subalpine forests

Tree‐ring data have become widely used to model tree growth responses to climate variability and gain insight about the potential effects of global warming on forests. We capitalized on a rare opportunity to develop growth–climate models using tree‐ring data collected from all trees (>4 cm in diameter at breast height) within 50 × 50 m plots established in subalpine old‐growth forests of western Canada. Our objective was to determine how tree growth responses to climate vary among tree size classes, species, and sites. We modeled relationships between times series of annual basal area increment (ΔBA) and yearly climate variables for individual trees; this approach obviated key statistical criticisms of “traditional” tree‐ring analysis methods. Time series of annual basal area increment were detrended a priori for size, age, legacy, and competition effects. We found that the overall climate signal in our time series of ΔBA was weak;