Browsing by Subject "Picae mariana"

The responses of understory saplings of black spruce (Picea mariana) and balsam fir (Abies balsamea) to overstory disturbances were studied in the Eastern Canadian boreal forest of Quebec‘s North Shore region. Death of the overstory trees causes an increase in available resources, leading to a growth release in the understory saplings. Two hypotheses were tested: 1) relative dominance, i.e. the size differences at the time of disturbance determine the post-disturbance canopy positions, and 2) rapid response, i.e. the capacity to quickly utilize resources released in a disturbance determine the post-disturbance canopy positions. To test these hypotheses, stem-disks were collected from saplings in unmanaged old-growth forests. Eight sample plots were selected with varying levels of domination by the two conifers. Dominant saplings from both species were selected from disturbed areas in each plot, as well as their strongest competitors from both species. The collected stem-disks were analyzed by a dendroecological method known as growth release analysis. The compositional development of mixed stands of P. mariana and A. balsamea in the North Shore region are largely driven by the prevalent disturbance regime, especially its effects on the ability of A. balsamea to establish and retain a dominant understory before and after a disturbance. In the absence of a disturbances that affect the established understory of A. balsamea, it is able to invade stands of pioneering P. mariana. If the post-disturbance sapling stand does not contain strongly enough established saplings of A.balsamea, P.mariana is able outgrow and increase dominance in relation to A.balsamea.