DISTURBANCE REGIME OF A COLD TEMPERATE FOREST AS DEDUCED FROM TREE-RING PATTERNS - THE TANTARE-ECOLOGICAL-RESERVE, QUEBEC

In an old-growth sugar maple Acer saccharum-yellow birch Betula alleghaniensis forest, the age, size and spatial pattern of gaps formed since the mid-19th century were inferred from tree-ring signatures of standing trees. From 1860 onwards, >30 gaps of various form and size occurred, most gaps being <200 m2 and covering a total area of 3775 m2. During 1930-1985, tree-fall frequency was 0.45 y-1, the tree fall free interval was 3.2 yr, and the tree-fall rotation period (turnover rate) was 45 yr. The rather short life-span of most trees (<125 yr) may be attributed to the cool and humid conditions prevailing at the site, which stimulated self-pruning of mature trees. The spatiotemporal development of the sugar maple forest has been active during the past 2 centuries through small-scale disturbances associated with successive, often overlapping, single and multiple tree falls. This situation explains the uneven age distribution of sugar maple and yellow birch populations subjected to differential survival conditions caused by gap dynamics. Tree-ring patterns corresponding to periods of suppression and release will likely give a finer resolution record of gap dynamics than other methods of determining natural disturbance regime and reconstruction of recent stand history. -from Authors