E-mail : lilywang15@hotmail.com

Black spruce growth as an indicator of climate change at the tree line in northern Quebec
Director : Serge Payette
Co-director : Yves Bégin 

Growth rings of black spruce (Picea mariana) obtained from the northern tree line were studied with the aid of a densitometer and image analysis. Several parameters related to these methods were used to analyze ring growth between 694 and 1994 AD in order to establish a long chronology. Of particular importance were the presence of light rings in the samples. These rings are formed by thin-walled latewood cells and are frequently found at the tree limit. The density and structure of these light rings were analyzed in order to better understand the mechanisms responsible to their formation The densiometric data obtained was significantly correlated with the three tree categories examined : living, dead, and subfossil. Ring width, however, was better correlated amongst the living trees than the dead or subfossil ones. The maximum density and the mean density of the latewood were significantly correlated with all of the temperature parameters examined. Finally, the widths of both the initial and latewood, as well as the total ring width, were strongly positively correlated with the July temperature. The light rings were indexed and then grouped into three classes according to maximum density. The thickness of the cell walls in the latewood is less than that of the early wood, although the diameter of the cells do not vary between the two types of rings. The factors responsible for the formation of the pale rings are related to cold summers or short growing seasons. The relationship between the double thickness of the cell walls and the diameter of the cells show a similar profile to that of the densiometric data. The correlation between the maximum proportions and the maximum density is highly significant (r : 0.66, p < 0.0001). A strong portion (83%) of the visibly lightest rings correspond with rings with thin cell walls. Sixteen of the rings were particularly identifiable within the image analysis and densiometric data and are associated with major volcanic eruptions.

Publications

Wang, L., Payette, S., Bégin, Y., 2002. Relationships between anatomical and densitometric characteristics of black spruce and summer temperature at tree line in northern Quebec. Canadian Journal of Forest Research, 32: 477-486.

Wang, L., Payette, S., Bégin, Y., 2001. 1300-year tree-ring width and density series based on living, dead and subfossil black spruce at tree-line in subarctic Québec, Canada. The Holocene, 11: 333-341.


Wang, L., Payette, S., Bégin, Y., 2000 A quantitative definition of light rings in black spruce (Picea mariana) at the arctic treeline in northern Québec, Canada. Arctic, Antarctic and Alpine Research, 32: 324-330.