Reproductive development and seed ripening inBetula papyriferaalong an altitudinal thermal gradient in eastern Appalachia (Canada)

Abstract

In several gymnosperm tree species of the circumboreal forest, reproductive development is closely associated with the accumulation of degree-days during the growing season. We wanted to verify whether this pattern holds for a widespread angiosperm species such as paper birch ( Betula papyrifera Marsh), a broadleaf tree distributed throughout the North American boreal forest. Stations to simultaneously measure the thermal sum (degree-days > 5 °C, DD) and the reproductive development (anatomical development and seed germination) were installed in four sites along an altitudinal thermal gradient totalling 541 m a.s.l. in the eastern Appalachian Mountains (Canada). In 2004, sites 1, 2, 3 and 4, received 973, 1099, 1266 and 1359 DD, respectively. A strong relationship was found between thermal sum and reproductive development (anatomical development: r2 > 0.90; seed germination r2 > 0.72). This relationship seems to be based on the absolute value of heat-sum received because (i) rates of reproductive development are twice as high in colder sites (1 and 2) than in warmer sites (3 and 4), and (ii) total seed germination did not differ among the sites. Along with this, we noted a lesser production of full seeds in colder sites, coupled with a higher success of germination in the coldest site (site 1), which appears to be a mechanism of phenotypic adaptation to cold.

Grasshopper Community Response to Climatic Change: Variation Along an Elevational Gradient

“…This will be important for many groups of organisms and may provide insight into why certain taxa respond to warming whereas others do not. In addition, as the utility of linking temperature, GDDs, and phenological development has shown in this study (see also [39] , [41] , [59] , [60] , [61] ), we suggest that through incorporation of GDDs into analyses and models of species and community responses, it will be possible to predict more precisely future phenological advancements based on different warming scenarios.…”

How climate change might affect tree regeneration following fire at northern latitudes: a review

“…For jack pine trees growing at the northern limit of their distribution range, higher than average temperatures during the three growing seasons required for seed production increase the production of viable seeds (Despland and Houle 1997). Similarly, paper birch produced more seeds on warmer sites in Appalachian forests (Grenier and Sirois 2009). Black spruce cone production does not increase with degree-days or maximum summer temperature in boreal Québec, Canada (Sirois 2000;Messaoud et al 2007), but the number of filled seeds (with embryo development) per cone is positively correlated with the cumulative number of degree-days (Sirois 2000).…”

“…For example, black spruce seeds germinate at temperatures > 15 °C (Black and Bliss 1980), or when the cumulative heat sum reaches from 800 to 940 degree-days (Meunier et al 2007). Germination success increases with both temperature and degree-days for black spruce (Hobbie and Chapin 1998;Sirois 2000;Munier et al 2010), paper birch (Hobbie and Chapin 1998;Grenier and Sirois 2009), and trembling aspen (Zasada and Viereck 1975;Hobbie and Chapin 1998), up to a maximum threshold. However, Grenier and Sirois (2009) found higher paper birch germination success on colder sites in Appalachian forests.…”