Dendroclimatic response of a coastal alpine treeline ecotone: a multispecies perspective from Labrador

Coastal alpine forests are highly vulnerable to oceanic climate trends, yet these diverse environmental interactions remain poorly understood. We used a multispecies perspective to try to better assess the radial growth response of alpine treeline species within the Northeast Atlantic region of North America to climate variables using bootstrapped correlation analysis. The four species present, black spruce (Picea mariana (Mill.) B.S.P.), white spruce (Picea glauca (Moench) Voss), balsam fir (Abies balsamea (L.) Mill.), and eastern larch (Larix laricina (Du Roi) K. Koch) were sampled in an effort to capture tree-climate sensitivity that is representative of this entire alpine treeline. The climate-growth relationships of spruce trees were comparable with those reported in other Labrador studies, but spring drought sensitivity as reported for coastal northern white spruce trees was not observed. Rather, high levels of precipitation suggest that drought did not limit the radial growth of any of the four species. The relatively small number of statistically significant correlations between monthly climate variables and fir and larch trees suggests that factors other than climate limit their radial growth. The multispecies approach better highlighted the range of species-specific relationships between alpine treeline forests and maritime climates (monthly temperature and precipitation) found at the treeline ecotone. Resume: Les forets alpines cotieres sont tres vulnerables aux tendances climatiques oceaniques bien que ces diverses interactions environnementales demeurent peu comprises. A l'aide d'une analyse de correlation par la methode bootstrap, nous avons utilise une perspective multispecifique pour tenter d'ameliorer l'estimation de la reaction en croissance radiale d'especes aux variables climatiques, a la limite alpine des arbres, dans la region du nord-est de l'Atlantique en Amerique du Nord. Les quatre especes presentes, l'epinette noire (Picea mariana (Mill.) B.S.P.), l'epinette blanche (Picea glauca (Moench) Voss), le sapin baumier (Abies balsamea (L.) Mill.) et le meleze laricin (Larix laricina (Du Roi) K. Koch), ont ete echantillonnees de facon a detecter une sensibilite entre l'arbre et le climat qui soit representative de l'ensemble de la limite alpine des arbres. La relation entre le climat et la croissance des epinettes etait comparable a celle rapportee par d'autres etudes realisees au Labrador, mais la sensibilite a la secheresse printaniere rapportee pour l'epinette blanche cotiere nordique n'a pas ete observee. Au contraire, de fortes precipitations indiquent que la secheresse n'a limite la croissance radiale d'aucune des quatre especes. Le nombre relativement faible de correlations statistiquement significatives entre les variables climatiques mensuelles et la croissance radiale du sapin et du meleze indiquent que des facteurs autres que le climat limitent leur croissance radiale. L'approche multispecifique a permis de mieux faire ressortir la gamme des relations propres a chaque espece entre les forets de la limite alpine des arbres et le climat maritime (temperature et precipitation mensuelles) de l'ecotone de la limite des arbres. [Traduit par la Redaction]
Introduction The climate of most coastal forests is regulated by the proximity of the ocean, which imparts a maritime climate to the region through a complex suite of forcing mechanisms [...]