The influence of winter temperatures on the annual radial growth of six northern range margin tree species

This study explores the influence of temperature on the growth of six northern range margin (NRM) tree species in the Hudson River Valley (HRV). The HRV has excellent geographic and floristic qualities to study the influence of climate change on forested ecosystems. Indices of radial growth for three populations per species are developed and correlated against average minimum and maximum monthly temperatures from 1897 to 1994. Only positive correlations to temperature are considered for this analysis. Principal component analysis (PCA) is performed on chronologies over the entire HRV and at four subregions. PCA reveals a strong common signal among populations at subregional and regional scales. January temperatures most limit growth at the ecosystem level, supporting the hypothesis that winter temperatures may control vegetational ecotones. Surprisingly, growth of the oak–hickory ecosystem is most limited by January temperatures only in the southern half of the study region. Chestnut and white oak are the primary species driving the geographic pattern. As winter xylem embolism is a constant factor for ringporous species, snow cover and its interaction on fine root mortality may be the leading factors of the pattern of temperature sensitivity. Species-specific differences in temperature sensitivity are apparent. Atlantic white-cedar (AWC) and pitch pine are more sensitive to the entire winter season (December–March) while oak and hickory are most sensitive to January temperatures. AWC is most sensitive species to temperature. Chestnut and white oak in the HRV are more sensitive to winter temperature than red oak. Pignut hickory has the most unique response with significant relations to late growing season temperatures. Interestingly, AWC and pitch pine are sensitive to winter temperatures at their NRM while oak and hickory are not. Our results suggest that temperature limitations of growth may be species and phylogenetically specific. They also indicate that the influence of temperature on radial growth at species and ecosystem levels may operate differently at varying geographic scales. If these results apply broadly to other temperate regions, winter temperatures may play an important role in the terrestrial carbon cycle. r 2004 Elsevier GmbH. All rights reserved.