Sensitivity of tree growth to the atmospheric vertical profile in the Boreal Plains of Manitoba, Canada

Abstract

This paper investigates the influence of surface climate and atmospheric circulation on radial growth of eight boreal tree species growing in the Duck Mountain Provincial Forest, Manitoba, Canada. Tree-ring residual chronologies were built, transformed into principal components (PCs), and analysed through correlation and response functions to reveal their associations to climate (temperature, precipitation, and drought data for the period 1912–1999, as well as local geopotential height data for the period 1948–1999). Geopotential height correlation and composite charts for the Northern Hemisphere were also constructed. Correlation and response function coefficients indicated that radial growth of all species was negatively affected by temperature-induced drought stresses from the summers previous and current to ring formation. The summer drought stress alone explained nearly 28% of the variance in PC1. Warm spring temperature was also a positive factor for Pinus banksiana Lamb. and Picea glauca (Moench) Voss, but a negative one for all hardwoods. Analyses performed on geopotential height highlighted the importance of the Northern Hemispheric atmospheric circulation in the species' response to climate. The variability within the 500-hPa level over southern Manitoba explained 39% and 58% of the variability in PC1 and PC2, respectively. The relationships were highly significant with the middle and high troposphere during spring and late summer (determinant factor for growing season length) and with the troposphere and stratosphere during summer. The sensitivity of tree growth to atmospheric circulation exceeded the synoptic scale, with a response associated with yearly variations in the amplitude of the mid-tropospheric longwaves.