Growth responses of three coexisting conifer species to climate variables across a range of climate conditions.

Tree ring analyses and an interpolated climate model (ClimateBC) were used to compare radial growth responses to climate variables among three coexisting, ecologically distinct conifer species, including interior spruce (Picea glauca x Picea Engelmannii), lodgepole pine (Pinus contorta var. latifolia) and subalpine fir (Abies lasiocarpa) across a range of climate conditions in western Canada, and altitudinal treelines in the Engelmann Spruce-Subalpine Fir forests in central British Columbia (BC). Ring-width chronologies were developed and correlated with site-specific climate data in the past 50 years from 1953-2002. June-July temperature appeared to be the dominant climate factor influencing radial growth of spruce across the sample sites, and the relationships changed from positive to negative as summer site temperature increased. Growth-climate relationships of lodgepole pine and subalpine fir varied within species. October-March temperatures appeared to be important for growth of lodgepole pine and subalpine fir at colder sites in BC. The Pacific Decadal Oscillation during October and March was also important for pine and fir at altitudinal treelines. Given the species- and site-specific growth responses to climate, future climate change will likely alter interactions among coexisting species, potentially leading to changes in species dominance, compositions and distribution of forest communities.--P.ii.