Gas exchange measurements were made with two portable open-path gas-exchange systems (Li-6400, Li-Cor, Lincoln, NE, USA), equipped with a Lighted Conifer Chamber (6400-22L, Li-Cor, Lincoln, NE, USA) and the expanded Temperature Control Kit (6400-88, Li-Cor, Lincoln, NE, USA). Temperature (T) response curves of shoot respiration (Rd–T) and net photosynthesis (An–T) were generated for one randomly selected plant per plot at each plantation site (2 seed sources × 3 blocks × 8 sites = 48). Both An–T and Rd–T curves were assessed using 1-year-old needles of the uppermost lateral shoot. The measurements were carried out in June 2015 in the plantations of Watford, Asselin, Deville, Wendover and Lac Bergeron, and in June 2016 in the plantations of Watford, Dorion, Picard and Rousseau. At the Watford, Asselin, Deville and Picard sites, plants were at their third growing season, whereas those at the remaining sites were at their second growing season. The results obtained in Watford during the third and fourth growing seasons were quite similar for thermal acclimation-related traits, which suggested the absence of an age effect on the observed patterns.