Reproductive potential of Balsam fir (Abies balsamea), White spruce (Picea glauca), and Black spruce (P. Mariana) at the ecotone between mixedwood and coniferous forests in the boreal zone of Western Quebec.
Yassine Messaoud, Yves Bergeron, Hugo Asselin.
The reproductive potentials of balsam fir and white spruce (co-dominants in mixedwood forests) and black spruce (dominant in
coniferous forests) were studied to explain the location of the ecotone between the two forest types in the boreal zone of Quebec.
Four sites were selected along a latitudinal gradient crossing the ecotone. Cone crop, number of seeds per cone, percentage filled
seeds, and percentage germination were measured for each species. Balsam fir and white spruce cone crops were significantly
lower in the coniferous than in the mixedwood forest, while black spruce had greater crop constancy and regularity between both
forest types. Mast years were more frequent for black spruce than for balsam fir in both forest types (mast year data not available
for white spruce). The number of seeds per cone was more related to cone size than to forest type for all species. Black spruce
produced more filled seeds in the coniferous forest than balsam fir or white spruce. The sum of growing degree-days and the
maximum temperature of the warmest month (both for the year prior to cone production) significantly affected balsam fir cone
production. The climate-related northward decrease in reproductive potential of balsam fir and white spruce could partly explain
the position of the northern limit of the mixedwood forest. This could change drastically, however, as the ongoing climate
warming might cancel this competitive advantage of black spruce.