2073 Population dynamics of black spruce and white spruce near the arctic tree line in the southern

• Main Authors: Andrea H. Lloyd, Alexis E. Wilson, Christopher L. Fastie, R. Matthew L
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Arctic; Blanche; Noire; Alaska
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.419.9785; http://www.lter.uaf.edu/pdf/974_lloyd_wilson_2005.pdf

Abstract: Black spruce (Picea mariana (Mill.) BSP) is the dominant species in interior Alaska but it is largely absent from the arctic tree line. To evaluate the importance of climate and fire as controls over the species distribution, we reconstructed stand history at three sites near its northern limit in Alaska, where it grows with white spruce (Picea glauca (Moench) Voss). We developed a matrix model to explore black spruce population dynamics and response to varying fire intervals. All sites burned in the early 1900s. High recruitment of black spruce occurred for <30 years following the fire, but most current black spruce recruitment is clonal and seed viability is low. White spruce recruitment has been consistently high since the fire, and the majority of seedlings in the stands are white spruce. Despite low recruitment, the matrix model suggests that black spruce populations are nearly stable, largely because of low adult mortality rates. Although black spruce recruitment is stimulated by fire, the model indicates that fire intervals <350 years would destabilize the population, primarily because of slow growth and low seed production. Population dynamics of black spruce at its northern limit in Alaska thus appear to reflect an interaction between fire, which determines the temporal pattern of tree recruitment, and climate, which limits tree growth and, presumably, viable seed production. Résumé: L’épinette noire (Picea mariana (Mill.) BSP) est l’espèce dominante dans la région intérieure de l’Alaska mais elle est presque absente à la limite des arbres dans l’Arctique. Pour évaluer l’importance du climat et du feu en tant que facteurs déterminants pour la répartition géographique de cette espèce, les auteurs ont reconstitué l’historique du peuplement à trois endroits situés près de sa limite nord en Alaska, où elle croît avec l’épinette blanche (Picea glauca (Moench) Voss). Ils ont développé un modèle matriciel pour étudier la dynamique de population de l’épinette