2001a: Dendroclimatic response of mountain hemlock (Tsuga mertensiana

Abstract: In this paper we review the ecology and physiology of mountain hemlock (Tsuga mertensiana (Bong.) Carrière) in the context of a dendroclimatological analysis. To better understand the relationship between mountain hemlock growth and climate variability throughout its range we have analyzed chronologies from 10 coastal sites, lo-cated along a transect extending from northern California to southern Alaska. The chronologies exhibit significant large-scale cross-correlations, with two distinct growth regions implied: chronologies from the northern Cascades in California, to the Queen Charlotte Islands, British Columbia, are correlated with each other but are distinct from Alas-kan chronologies. While intervals of coherent reduced growth along the entire transect occur episodically throughout the record, intervals of coherent enhanced growth are less common. Response function analyses indicate that summer temperature is the most influential factor limiting growth throughout the study region, while winter precipitation is an additional limiting factor south of Alaska. Warm summer temperatures are associated with enhanced growth in the cur-rent year but with reduced growth in the following year. This response is believed to be a reflection of the energy re-quired to mature cones initiated in the preceding year. The association with winter precipitation may reflect the role of deep, persistent snowpacks in regulating the duration of the growing season. Résumé: Dans cet article, les auteurs réexaminent l’écologie et la physiologie de la pruche subalpine (Tsuga merten-siana (Bong.) Carrière) dans le cadre d’une analyse dendroclimatologique. Afin de mieux comprendre la relation entr