Radial-Growth Response of Forest-Tundra Trees to Climate in the Western Hudson Bay Lowlands

Abstract

ABSTRACT. The effects of climate on radial growth of Larix laricina (Du Roi) K. Koch, Picea glauca (Moench) Voss, and Picea mariana (Mill) BSP were investigated in the Hudson Bay Lowlands of northern Manitoba. The objective was to characterize spatial and temporal variations in growth of trees across the forest-tundra ecotone. Along a 250 km transect, 299 trees were sampled in three zones: northern forest, central tundra, and southern forest. Ring-width indices were compared with climate through correlation-and response-function analyses. Numerous years of suppressed growth at the three locales resulted from cooling that followed major volcanic eruptions at much lower latitudes. Temperatures during July of the current year and autumn of the previous year were most limiting, particularly for L. laricina, which was temperature-sensitive across the region. A weakened growth response to temperature during the 1940-60 period was likely due to atmospheric circulation shifts. Most chronologies were intercorrelated, which suggests common environmental forcing, though environmental influences differed in the southern forest (particularly for P. mariana). The source of this disparity has yet to be determined.

Ecophysiological modeling of photosynthesis and carbon allocation to the tree stem in the boreal forest

“…As expected, the ring growth variability at our sites was more linked to temperature than to precipitation variables (see Fig. 4a and Gennaretti et al, 2014;Mamet and Kershaw, 2011;Nicault et al, 2014). The model reproduced this correlation pattern (Fig.…”

“…Contrasting correlations with summer temperature values of the previous and the current growing year are also visible in Fig. 4a and have already been observed for black spruce (Mamet and Kershaw, 2011;Ols et al, 2016).…”

“…However, at the beginning of each year, the model defines the maximum amount of carbon that the canopy can potentially contain that year (AlloCcanopy j ; g C m −2 of stand) as a function of previous-year climate variables. Based on previous studies on black spruce forests (Girardin et al, 2016;Ols et al, 2016;Mamet and Kershaw, 2011), we modified the model to consider the effect of the previous-year April precipitation and July-August temperature that likely influence the length and the thermal-hydraulic stress of the previous growing season, respectively. Previous-year climate conditions of specific months are known to influence the shoot extension of boreal trees likely because they control the accumulation of resources in the buds (Salminen and Jalkanen, 2005).…”

Ecophysiological modeling of the climate imprint on photosynthesis and carbon allocation to the tree stem in the North American boreal forest

“…As expected, the ring growth variability at our sites was more linked to temperature than precipitation variables (see Fig. 6 and Gennaretti et al, 2014;Mamet and Kershaw, 2011;Nicault et al, 2014). The model explained about 20-30% of the observed yearly RWhighF variability corresponding to correlations of 0.58-0.66 (Fig.…”

“…However, at the beginning of each year, the model defines the maximum amount of carbon that the canopy can potentially contain that year (AlloCcanopy j ; g C m -2 of stand) as a 10 function of previous year climate variables. Based on a correlation analysis (see our results below) and on previous studies on black spruce forests (Girardin et al, 2016;Ols et al, 2016;Mamet and Kershaw, 2011), we modified the model to consider the effect of the previous year July-August temperature and April precipitation in replacement of the mean soil water content for May-December of the previous year such as in Gea-Izquierdo et al (2015). Previous year climate conditions of specific months are known to influence shoot extension of boreal trees likely because they control 15 accumulation of resources in the buds (Salminen and Jalkanen, 2005).…”