Mariana Trindade
Dendrochronology
A central component of our studies is the reconstruction of past climate and vegetation from indirect or “proxy” evidence. For the recent past, the annual growth rings of living and dead trees provide information about the age of the trees and about growing-conditions (dendrochronology). Sampling is done on selected trees in the region by taking small cores.
Previous studies of this kind have been done elsewhere in Newfoundland and Labrador, but generally not in the higher elevations. Sampling of White Spruce (Picea glauca) was done previously in the southern Mealy Mountains by Schweingruber (1993) as part of a large-scale Alaska to Labrador study. Those data, which span over two centuries, have been obtained for use in our study. Our focus is on the regional and local scale, hence our sampling is more intense. In addition to tree ages, and growth-climate relationship at treeline, this information will provide us with a means of producing a climate-ring width relationship for the area, which we will extend using cross-dating techniques.
In order to better understand treeline dynamics in Gros Morne National Park, tree samples were collected on Big Level at a range of altitudes. Samples consisted of both cores and disks (cross sections, of dead trees only). A total of 16 tree samples were collected, including 12 tree disks. Average age of live trees (cores) was 56, with 87 and 23 years being the oldest and youngest trees sampled, respectively. By contrast, disks (representing dead trees) were on average 38.58 years old, with the oldest being 68 and the youngest 6 years old.
Similar to Gros Morne, tree samples were collected in the Mealy Mountains study area through a range of altitudes near present tree-line. A total of four tree disks were sampled, and 19 trees were cored. Cores sampled (live trees) yielded an average age of 90.7 years, with the oldest living tree sampled being 183, and the youngest 55 years. By contrast, disks were on average 109.5, with the youngest being 6 and the oldest 161 years old. Crosscorrelations between live and dead trees have yet to be done.
Many of these older White Spruce are found growing above the present altitudinal limit in a zone where Black Spruce (P. mariana) and Balsam Fir (Abies balsamea) grow only in krummholz form (that is, as low, dense shrubs, locally known as ‘tuckamore’). These erect White Spruce are either survivors of a past period of more favourable growing conditions in the region or reflect locally anomalous conditions. They are a clear indication of the potential for the forest to advance to higher elevations in both areas.
